1 | (* *********************************************************************) |
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2 | (* *) |
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3 | (* The Compcert verified compiler *) |
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4 | (* *) |
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5 | (* Xavier Leroy, INRIA Paris-Rocquencourt *) |
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6 | (* *) |
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7 | (* Copyright Institut National de Recherche en Informatique et en *) |
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8 | (* Automatique. All rights reserved. This file is distributed *) |
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9 | (* under the terms of the GNU General Public License as published by *) |
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10 | (* the Free Software Foundation, either version 2 of the License, or *) |
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11 | (* (at your option) any later version. This file is also distributed *) |
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12 | (* under the terms of the INRIA Non-Commercial License Agreement. *) |
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13 | (* *) |
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14 | (* *********************************************************************) |
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15 | |
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16 | (* * Abstract syntax for the Clight language *) |
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17 | |
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18 | (*include "Integers.ma".*) |
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19 | include "common/AST.ma". |
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20 | include "utilities/Coqlib.ma". |
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21 | include "common/Errors.ma". |
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22 | include "common/CostLabel.ma". |
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23 | |
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24 | (* * * Abstract syntax *) |
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25 | |
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26 | (* * ** Types *) |
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27 | |
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28 | (* * The syntax of type expressions. Some points to note: |
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29 | - Array types [Tarray n] carry the size [n] of the array. |
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30 | Arrays with unknown sizes are represented by pointer types. |
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31 | - Function types [Tfunction targs tres] specify the number and types |
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32 | of the function arguments (list [targs]), and the type of the |
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33 | function result ([tres]). Variadic functions and old-style unprototyped |
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34 | functions are not supported. |
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35 | - In C, struct and union types are named and compared by name. |
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36 | This enables the definition of recursive struct types such as |
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37 | << |
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38 | struct s1 { int n; struct * s1 next; }; |
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39 | >> |
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40 | Note that recursion within types must go through a pointer type. |
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41 | For instance, the following is not allowed in C. |
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42 | << |
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43 | struct s2 { int n; struct s2 next; }; |
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44 | >> |
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45 | In Clight, struct and union types [Tstruct id fields] and |
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46 | [Tunion id fields] are compared by structure: the [fields] |
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47 | argument gives the names and types of the members. The identifier |
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48 | [id] is a local name which can be used in conjuction with the |
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49 | [Tcomp_ptr] constructor to express recursive types. [Tcomp_ptr rg id] |
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50 | stands for a pointer type to the nearest enclosing [Tstruct] |
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51 | or [Tunion] type named [id] in memory region [rg]. For instance. |
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52 | the structure [s1] defined above in C is expressed by |
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53 | << |
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54 | Tstruct "s1" (Fcons "n" (Tint I32 Signed) |
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55 | (Fcons "next" (Tcomp_ptr Any "id") |
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56 | Fnil)) |
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57 | >> |
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58 | Note that the incorrect structure [s2] above cannot be expressed at |
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59 | all, since [Tcomp_ptr] lets us refer to a pointer to an enclosing |
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60 | structure or union, but not to the structure or union directly. |
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61 | *) |
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62 | |
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63 | inductive type : Type[0] ≝ |
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64 | | Tvoid: type (**r the [void] type *) |
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65 | | Tint: intsize → signedness → type (**r integer types *) |
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66 | | Tpointer: (*region →*) type → type (**r pointer types ([*ty]) *) |
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67 | | Tarray: (*region →*) type → nat → type (**r array types ([ty[len]]) *) |
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68 | | Tfunction: typelist → type → type (**r function types *) |
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69 | | Tstruct: ident → fieldlist → type (**r struct types *) |
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70 | | Tunion: ident → fieldlist → type (**r union types *) |
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71 | | Tcomp_ptr: (*region →*) ident → type (**r pointer to named struct or union *) |
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72 | |
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73 | with typelist : Type[0] ≝ |
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74 | | Tnil: typelist |
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75 | | Tcons: type → typelist → typelist |
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76 | |
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77 | with fieldlist : Type[0] ≝ |
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78 | | Fnil: fieldlist |
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79 | | Fcons: ident → type → fieldlist → fieldlist. |
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80 | |
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81 | (* XXX: no induction scheme! *) |
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82 | let rec type_ind |
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83 | (P:type → Prop) |
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84 | (vo:P Tvoid) |
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85 | (it:∀i,s. P (Tint i s)) |
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86 | (pt:∀t. P t → P (Tpointer t)) |
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87 | (ar:∀t,n. P t → P (Tarray t n)) |
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88 | (fn:∀tl,t. P t → P (Tfunction tl t)) |
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89 | (st:∀i,fl. P (Tstruct i fl)) |
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90 | (un:∀i,fl. P (Tunion i fl)) |
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91 | (cp:∀i. P (Tcomp_ptr i)) |
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92 | (t:type) on t : P t ≝ |
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93 | match t return λt'.P t' with |
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94 | [ Tvoid ⇒ vo |
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95 | | Tint i s ⇒ it i s |
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96 | | Tpointer t' ⇒ pt t' (type_ind P vo it pt ar fn st un cp t') |
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97 | | Tarray t' n ⇒ ar t' n (type_ind P vo it pt ar fn st un cp t') |
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98 | | Tfunction tl t' ⇒ fn tl t' (type_ind P vo it pt ar fn st un cp t') |
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99 | | Tstruct i fs ⇒ st i fs |
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100 | | Tunion i fs ⇒ un i fs |
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101 | | Tcomp_ptr i ⇒ cp i |
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102 | ]. |
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103 | |
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104 | let rec fieldlist_ind |
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105 | (P:fieldlist → Prop) |
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106 | (nl:P Fnil) |
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107 | (cs:∀i,t,fs. P fs → P (Fcons i t fs)) |
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108 | (fs:fieldlist) on fs : P fs ≝ |
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109 | match fs with |
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110 | [ Fnil ⇒ nl |
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111 | | Fcons i t fs' ⇒ cs i t fs' (fieldlist_ind P nl cs fs') |
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112 | ]. |
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113 | |
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114 | (* * ** Expressions *) |
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115 | |
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116 | (* * Arithmetic and logical operators. *) |
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117 | |
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118 | inductive unary_operation : Type[0] ≝ |
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119 | | Onotbool : unary_operation (**r boolean negation ([!] in C) *) |
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120 | | Onotint : unary_operation (**r integer complement ([~] in C) *) |
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121 | | Oneg : unary_operation. (**r opposite (unary [-]) *) |
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122 | |
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123 | inductive binary_operation : Type[0] ≝ |
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124 | | Oadd : binary_operation (**r addition (binary [+]) *) |
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125 | | Osub : binary_operation (**r subtraction (binary [-]) *) |
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126 | | Omul : binary_operation (**r multiplication (binary [*]) *) |
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127 | | Odiv : binary_operation (**r division ([/]) *) |
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128 | | Omod : binary_operation (**r remainder ([%]) *) |
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129 | | Oand : binary_operation (**r bitwise and ([&]) *) |
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130 | | Oor : binary_operation (**r bitwise or ([|]) *) |
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131 | | Oxor : binary_operation (**r bitwise xor ([^]) *) |
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132 | | Oshl : binary_operation (**r left shift ([<<]) *) |
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133 | | Oshr : binary_operation (**r right shift ([>>]) *) |
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134 | | Oeq: binary_operation (**r comparison ([==]) *) |
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135 | | One: binary_operation (**r comparison ([!=]) *) |
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136 | | Olt: binary_operation (**r comparison ([<]) *) |
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137 | | Ogt: binary_operation (**r comparison ([>]) *) |
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138 | | Ole: binary_operation (**r comparison ([<=]) *) |
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139 | | Oge: binary_operation. (**r comparison ([>=]) *) |
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140 | |
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141 | (* * Clight expressions are a large subset of those of C. |
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142 | The main omissions are string literals and assignment operators |
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143 | ([=], [+=], [++], etc). In Clight, assignment is a statement, |
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144 | not an expression. |
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145 | |
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146 | All expressions are annotated with their types. An expression |
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147 | (type [expr]) is therefore a pair of a type and an expression |
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148 | description (type [expr_descr]). |
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149 | *) |
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150 | |
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151 | inductive expr : Type[0] ≝ |
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152 | | Expr: expr_descr → type → expr |
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153 | |
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154 | with expr_descr : Type[0] ≝ |
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155 | | Econst_int: ∀sz:intsize. bvint sz → expr_descr (**r integer literal *) |
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156 | | Evar: ident → expr_descr (**r variable *) |
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157 | | Ederef: expr → expr_descr (**r pointer dereference (unary [*]) *) |
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158 | | Eaddrof: expr → expr_descr (**r address-of operator ([&]) *) |
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159 | | Eunop: unary_operation → expr → expr_descr (**r unary operation *) |
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160 | | Ebinop: binary_operation → expr → expr → expr_descr (**r binary operation *) |
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161 | | Ecast: type → expr → expr_descr (**r type cast ([(ty) e]) *) |
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162 | | Econdition: expr → expr → expr → expr_descr (**r conditional ([e1 ? e2 : e3]) *) |
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163 | | Eandbool: expr → expr → expr_descr (**r sequential and ([&&]) *) |
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164 | | Eorbool: expr → expr → expr_descr (**r sequential or ([||]) *) |
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165 | | Esizeof: type → expr_descr (**r size of a type *) |
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166 | | Efield: expr → ident → expr_descr (**r access to a member of a struct or union *) |
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167 | | Ecost: costlabel → expr → expr_descr. |
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168 | |
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169 | |
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170 | |
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171 | |
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172 | (* * Extract the type part of a type-annotated Clight expression. *) |
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173 | |
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174 | definition typeof : expr → type ≝ λe. |
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175 | match e with [ Expr de te ⇒ te ]. |
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176 | |
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177 | (* * ** Statements *) |
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178 | |
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179 | (* * Clight statements include all C statements. |
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180 | Only structured forms of [switch] are supported; moreover, |
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181 | the [default] case must occur last. Blocks and block-scoped declarations |
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182 | are not supported. *) |
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183 | |
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184 | definition label ≝ ident. |
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185 | |
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186 | inductive statement : Type[0] ≝ |
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187 | | Sskip : statement (**r do nothing *) |
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188 | | Sassign : expr → expr → statement (**r assignment [lvalue = rvalue] *) |
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189 | | Scall: option expr → expr → list expr → statement (**r function call *) |
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190 | | Ssequence : statement → statement → statement (**r sequence *) |
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191 | | Sifthenelse : expr → statement → statement → statement (**r conditional *) |
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192 | | Swhile : expr → statement → statement (**r [while] loop *) |
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193 | | Sdowhile : expr → statement → statement (**r [do] loop *) |
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194 | | Sfor: statement → expr → statement → statement → statement (**r [for] loop *) |
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195 | | Sbreak : statement (**r [break] statement *) |
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196 | | Scontinue : statement (**r [continue] statement *) |
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197 | | Sreturn : option expr → statement (**r [return] statement *) |
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198 | | Sswitch : expr → labeled_statements → statement (**r [switch] statement *) |
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199 | | Slabel : label → statement → statement |
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200 | | Sgoto : label → statement |
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201 | | Scost : costlabel → statement → statement |
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202 | |
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203 | with labeled_statements : Type[0] ≝ (**r cases of a [switch] *) |
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204 | | LSdefault: statement → labeled_statements |
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205 | | LScase: ∀sz:intsize. bvint sz → statement → labeled_statements → labeled_statements. |
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206 | |
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207 | let rec labeled_statements_ind |
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208 | (P:labeled_statements → Prop) |
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209 | (LSd:∀s. P (LSdefault s)) |
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210 | (LSc:∀sz,i,s,tl. P tl → P (LScase sz i s tl)) |
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211 | ls on ls : P ls ≝ |
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212 | match ls with |
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213 | [ LSdefault s ⇒ LSd s |
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214 | | LScase sz i s tl ⇒ LSc sz i s tl (labeled_statements_ind P LSd LSc tl) |
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215 | ]. |
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216 | |
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217 | let rec statement_ind2 |
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218 | (P:statement → Prop) (Q:labeled_statements → Prop) |
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219 | (Ssk:P Sskip) |
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220 | (Sas:∀e1,e2. P (Sassign e1 e2)) |
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221 | (Sca:∀eo,e,args. P (Scall eo e args)) |
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222 | (Ssq:∀s1,s2. P s1 → P s2 → P (Ssequence s1 s2)) |
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223 | (Sif:∀e,s1,s2. P s1 → P s2 → P (Sifthenelse e s1 s2)) |
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224 | (Swh:∀e,s. P s → P (Swhile e s)) |
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225 | (Sdo:∀e,s. P s → P (Sdowhile e s)) |
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226 | (Sfo:∀s1,e,s2,s3. P s1 → P s2 → P s3 → P (Sfor s1 e s2 s3)) |
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227 | (Sbr:P Sbreak) |
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228 | (Sco:P Scontinue) |
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229 | (Sre:∀eo. P (Sreturn eo)) |
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230 | (Ssw:∀e,ls. Q ls → P (Sswitch e ls)) |
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231 | (Sla:∀l,s. P s → P (Slabel l s)) |
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232 | (Sgo:∀l. P (Sgoto l)) |
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233 | (Scs:∀l,s. P s → P (Scost l s)) |
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234 | (LSd:∀s. P s → Q (LSdefault s)) |
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235 | (LSc:∀sz,i,s,t. P s → Q t → Q (LScase sz i s t)) |
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236 | (s:statement) on s : P s ≝ |
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237 | match s with |
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238 | [ Sskip ⇒ Ssk |
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239 | | Sassign e1 e2 ⇒ Sas e1 e2 |
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240 | | Scall eo e args ⇒ Sca eo e args |
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241 | | Ssequence s1 s2 ⇒ Ssq s1 s2 |
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242 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s1) |
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243 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s2) |
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244 | | Sifthenelse e s1 s2 ⇒ Sif e s1 s2 |
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245 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s1) |
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246 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s2) |
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247 | | Swhile e s ⇒ Swh e s |
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248 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s) |
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249 | | Sdowhile e s ⇒ Sdo e s |
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250 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s) |
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251 | | Sfor s1 e s2 s3 ⇒ Sfo s1 e s2 s3 |
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252 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s1) |
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253 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s2) |
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254 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s3) |
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255 | | Sbreak ⇒ Sbr |
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256 | | Scontinue ⇒ Sco |
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257 | | Sreturn eo ⇒ Sre eo |
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258 | | Sswitch e ls ⇒ Ssw e ls |
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259 | (labeled_statements_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc ls) |
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260 | | Slabel l s ⇒ Sla l s |
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261 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s) |
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262 | | Sgoto l ⇒ Sgo l |
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263 | | Scost l s ⇒ Scs l s |
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264 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s) |
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265 | ] |
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266 | and labeled_statements_ind2 |
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267 | (P:statement → Prop) (Q:labeled_statements → Prop) |
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268 | (Ssk:P Sskip) |
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269 | (Sas:∀e1,e2. P (Sassign e1 e2)) |
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270 | (Sca:∀eo,e,args. P (Scall eo e args)) |
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271 | (Ssq:∀s1,s2. P s1 → P s2 → P (Ssequence s1 s2)) |
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272 | (Sif:∀e,s1,s2. P s1 → P s2 → P (Sifthenelse e s1 s2)) |
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273 | (Swh:∀e,s. P s → P (Swhile e s)) |
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274 | (Sdo:∀e,s. P s → P (Sdowhile e s)) |
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275 | (Sfo:∀s1,e,s2,s3. P s1 → P s2 → P s3 → P (Sfor s1 e s2 s3)) |
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276 | (Sbr:P Sbreak) |
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277 | (Sco:P Scontinue) |
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278 | (Sre:∀eo. P (Sreturn eo)) |
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279 | (Ssw:∀e,ls. Q ls → P (Sswitch e ls)) |
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280 | (Sla:∀l,s. P s → P (Slabel l s)) |
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281 | (Sgo:∀l. P (Sgoto l)) |
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282 | (Scs:∀l,s. P s → P (Scost l s)) |
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283 | (LSd:∀s. P s → Q (LSdefault s)) |
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284 | (LSc:∀sz,i,s,t. P s → Q t → Q (LScase sz i s t)) |
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285 | (ls:labeled_statements) on ls : Q ls ≝ |
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286 | match ls with |
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287 | [ LSdefault s ⇒ LSd s |
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288 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s) |
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289 | | LScase sz i s t ⇒ LSc sz i s t |
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290 | (statement_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc s) |
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291 | (labeled_statements_ind2 P Q Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs LSd LSc t) |
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292 | ]. |
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293 | |
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294 | definition statement_ind ≝ λP,Ssk,Sas,Sca,Ssq,Sif,Swh,Sdo,Sfo,Sbr,Sco,Sre,Ssw,Sla,Sgo,Scs. |
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295 | statement_ind2 P (λ_.True) Ssk Sas Sca Ssq Sif Swh Sdo Sfo Sbr Sco Sre Ssw Sla Sgo Scs |
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296 | (λ_,_. I) (λ_,_,_,_,_,_.I). |
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297 | |
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298 | (* * ** Functions *) |
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299 | |
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300 | (* * A function definition is composed of its return type ([fn_return]), |
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301 | the names and types of its parameters ([fn_params]), the names |
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302 | and types of its local variables ([fn_vars]), and the body of the |
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303 | function (a statement, [fn_body]). *) |
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304 | |
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305 | record function : Type[0] ≝ { |
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306 | fn_return: type; |
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307 | fn_params: list (ident × type); |
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308 | fn_vars: list (ident × type); |
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309 | fn_body: statement |
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310 | }. |
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311 | |
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312 | (* * Functions can either be defined ([CL_Internal]) or declared as |
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313 | external functions ([CL_External]). Similar to the AST definition, but |
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314 | with high level type information for external functions. *) |
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315 | |
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316 | inductive clight_fundef : Type[0] ≝ |
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317 | | CL_Internal: function → clight_fundef |
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318 | | CL_External: ident → typelist → type → clight_fundef. |
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319 | |
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320 | (* * ** Programs *) |
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321 | |
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322 | (* * A program is a collection of named functions, plus a collection |
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323 | of named global variables, carrying their types and optional initialization |
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324 | data. See module [AST] for more details. *) |
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325 | |
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326 | definition clight_program : Type[0] ≝ program (λ_.clight_fundef) (list init_data × type). |
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327 | |
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328 | (* * * Operations over types *) |
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329 | |
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330 | (* * The type of a function definition. *) |
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331 | |
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332 | let rec type_of_params (params: list (ident × type)) : typelist ≝ |
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333 | match params with |
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334 | [ nil ⇒ Tnil |
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335 | | cons h rem ⇒ let 〈id,ty〉 ≝ h in Tcons ty (type_of_params rem) |
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336 | ]. |
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337 | |
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338 | definition type_of_function : function → type ≝ λf. |
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339 | Tfunction (type_of_params (fn_params f)) (fn_return f). |
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340 | |
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341 | definition type_of_fundef : clight_fundef → type ≝ λf. |
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342 | match f with |
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343 | [ CL_Internal fd ⇒ type_of_function fd |
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344 | | CL_External id args res ⇒ Tfunction args res |
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345 | ]. |
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346 | |
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347 | (* * Natural alignment of a type, in bytes. *) |
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348 | let rec alignof (t: type) : nat ≝ (*1*) |
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349 | (* these are old values for 32 bit machines *) |
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350 | match t with |
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351 | [ Tvoid ⇒ 1 |
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352 | | Tint sz _ ⇒ match sz with [ I8 ⇒ 1 | I16 ⇒ 2 | I32 ⇒ 4 ] |
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353 | | Tpointer _ ⇒ 4 |
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354 | | Tarray t' n ⇒ alignof t' |
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355 | | Tfunction _ _ ⇒ 1 |
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356 | | Tstruct _ fld ⇒ alignof_fields fld |
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357 | | Tunion _ fld ⇒ alignof_fields fld |
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358 | | Tcomp_ptr _ ⇒ 4 |
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359 | ] |
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360 | |
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361 | and alignof_fields (f: fieldlist) : nat ≝ |
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362 | match f with |
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363 | [ Fnil ⇒ 1 |
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364 | | Fcons id t f' ⇒ max (alignof t) (alignof_fields f') |
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365 | ]. |
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366 | |
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367 | (* |
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368 | Scheme type_ind2 := Induction for type Sort Prop |
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369 | with fieldlist_ind2 := Induction for fieldlist Sort Prop. |
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370 | *) |
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371 | |
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372 | (* XXX: automatic generation? *) |
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373 | let rec type_ind2 |
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374 | (P:type → Prop) (Q:fieldlist → Prop) |
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375 | (vo:P Tvoid) |
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376 | (it:∀i,s. P (Tint i s)) |
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377 | (pt:∀t. P t → P (Tpointer t)) |
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378 | (ar:∀t,n. P t → P (Tarray t n)) |
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379 | (fn:∀tl,t. P t → P (Tfunction tl t)) |
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380 | (st:∀i,fl. Q fl → P (Tstruct i fl)) |
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381 | (un:∀i,fl. Q fl → P (Tunion i fl)) |
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382 | (cp:∀i. P (Tcomp_ptr i)) |
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383 | (nl:Q Fnil) |
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384 | (cs:∀i,t,f'. P t → Q f' → Q (Fcons i t f')) |
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385 | (t:type) on t : P t ≝ |
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386 | match t return λt'.P t' with |
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387 | [ Tvoid ⇒ vo |
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388 | | Tint i s ⇒ it i s |
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389 | | Tpointer t' ⇒ pt t' (type_ind2 P Q vo it pt ar fn st un cp nl cs t') |
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390 | | Tarray t' n ⇒ ar t' n (type_ind2 P Q vo it pt ar fn st un cp nl cs t') |
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391 | | Tfunction tl t' ⇒ fn tl t' (type_ind2 P Q vo it pt ar fn st un cp nl cs t') |
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392 | | Tstruct i fs ⇒ st i fs (fieldlist_ind2 P Q vo it pt ar fn st un cp nl cs fs) |
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393 | | Tunion i fs ⇒ un i fs (fieldlist_ind2 P Q vo it pt ar fn st un cp nl cs fs) |
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394 | | Tcomp_ptr i ⇒ cp i |
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395 | ] |
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396 | and fieldlist_ind2 |
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397 | (P:type → Prop) (Q:fieldlist → Prop) |
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398 | (vo:P Tvoid) |
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399 | (it:∀i,s. P (Tint i s)) |
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400 | (pt:∀t. P t → P (Tpointer t)) |
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401 | (ar:∀t,n. P t → P (Tarray t n)) |
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402 | (fn:∀tl,t. P t → P (Tfunction tl t)) |
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403 | (st:∀i,fl. Q fl → P (Tstruct i fl)) |
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404 | (un:∀i,fl. Q fl → P (Tunion i fl)) |
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405 | (cp:∀i. P (Tcomp_ptr i)) |
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406 | (nl:Q Fnil) |
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407 | (cs:∀i,t,f'. P t → Q f' → Q (Fcons i t f')) |
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408 | (fs:fieldlist) on fs : Q fs ≝ |
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409 | match fs return λfs'.Q fs' with |
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410 | [ Fnil ⇒ nl |
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411 | | Fcons i t f' ⇒ cs i t f' (type_ind2 P Q vo it pt ar fn st un cp nl cs t) |
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412 | (fieldlist_ind2 P Q vo it pt ar fn st un cp nl cs f') |
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413 | ]. |
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414 | |
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415 | lemma alignof_fields_pos: |
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416 | ∀f. alignof_fields f > 0. |
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417 | @fieldlist_ind //; |
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418 | #i #t #fs' #IH @max_r @IH qed. |
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419 | |
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420 | lemma alignof_pos: |
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421 | ∀t. alignof t > 0. |
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422 | #t elim t; normalize; //; |
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423 | [ 1,2: #z cases z; /2/; |
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424 | | 3,4: #i @alignof_fields_pos |
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425 | ] qed. |
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426 | |
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427 | (* * Size of a type, in bytes. *) |
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428 | |
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429 | let rec sizeof (t: type) : nat ≝ |
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430 | match t with |
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431 | [ Tvoid ⇒ 1 |
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432 | | Tint i _ ⇒ match i with [ I8 ⇒ 1 | I16 ⇒ 2 | I32 ⇒ 4 ] |
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433 | | Tpointer _ ⇒ size_pointer |
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434 | | Tarray t' n ⇒ sizeof t' * max 1 n |
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435 | | Tfunction _ _ ⇒ 1 |
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436 | | Tstruct _ fld ⇒ align (max 1 (sizeof_struct fld 0)) (alignof t) |
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437 | | Tunion _ fld ⇒ align (max 1 (sizeof_union fld)) (alignof t) |
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438 | | Tcomp_ptr _ ⇒ size_pointer |
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439 | ] |
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440 | |
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441 | and sizeof_struct (fld: fieldlist) (pos: nat) on fld : nat ≝ |
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442 | match fld with |
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443 | [ Fnil ⇒ pos |
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444 | | Fcons id t fld' ⇒ sizeof_struct fld' (align pos (alignof t) + sizeof t) |
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445 | ] |
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446 | |
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447 | and sizeof_union (fld: fieldlist) : nat ≝ |
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448 | match fld with |
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449 | [ Fnil ⇒ 0 |
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450 | | Fcons id t fld' ⇒ max (sizeof t) (sizeof_union fld') |
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451 | ]. |
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452 | (* TODO: needs some Z_times results |
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453 | lemma sizeof_pos: |
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454 | ∀t. sizeof t > 0. |
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455 | #t0 |
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456 | napply (type_ind2 (λt. sizeof t > 0) |
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457 | (λf. sizeof_union f ≥ 0 ∧ ∀pos:Z. pos ≥ 0 → sizeof_struct f pos ≥ 0)); |
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458 | [ 1,4,6,9: //; |
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459 | | #i cases i;#s //; |
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460 | | #f cases f;// |
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461 | | #t #n #H whd in ⊢ (?%?); |
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462 | Proof. |
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463 | intro t0. |
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464 | apply (type_ind2 (fun t => sizeof t > 0) |
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465 | (fun f => sizeof_union f >= 0 /\ forall pos, pos >= 0 -> sizeof_struct f pos >= 0)); |
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466 | intros; simpl; auto; try omega. |
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467 | destruct i; omega. |
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468 | destruct f; omega. |
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469 | apply Zmult_gt_0_compat. auto. generalize (Zmax1 1 z); omega. |
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470 | destruct H. |
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471 | generalize (align_le (Zmax 1 (sizeof_struct f 0)) (alignof_fields f) (alignof_fields_pos f)). |
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472 | generalize (Zmax1 1 (sizeof_struct f 0)). omega. |
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473 | generalize (align_le (Zmax 1 (sizeof_union f)) (alignof_fields f) (alignof_fields_pos f)). |
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474 | generalize (Zmax1 1 (sizeof_union f)). omega. |
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475 | split. omega. auto. |
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476 | destruct H0. split; intros. |
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477 | generalize (Zmax2 (sizeof t) (sizeof_union f)). omega. |
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478 | apply H1. |
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479 | generalize (align_le pos (alignof t) (alignof_pos t)). omega. |
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480 | Qed. |
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481 | |
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482 | Lemma sizeof_struct_incr: |
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483 | forall fld pos, pos <= sizeof_struct fld pos. |
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484 | Proof. |
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485 | induction fld; intros; simpl. omega. |
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486 | eapply Zle_trans. 2: apply IHfld. |
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487 | apply Zle_trans with (align pos (alignof t)). |
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488 | apply align_le. apply alignof_pos. |
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489 | assert (sizeof t > 0) by apply sizeof_pos. omega. |
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490 | Qed. |
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491 | |
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492 | (** Byte offset for a field in a struct or union. |
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493 | Field are laid out consecutively, and padding is inserted |
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494 | to align each field to the natural alignment for its type. *) |
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495 | |
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496 | Open Local Scope string_scope. |
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497 | *) |
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498 | axiom UnknownField : String. |
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499 | |
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500 | let rec field_offset_rec (id: ident) (fld: fieldlist) (pos: nat) |
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501 | on fld : res nat ≝ |
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502 | match fld with |
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503 | [ Fnil ⇒ Error ? [MSG UnknownField (*"Unknown field "*); CTX ? id] |
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504 | | Fcons id' t fld' ⇒ |
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505 | match ident_eq id id' with |
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506 | [ inl _ ⇒ OK ? (align pos (alignof t)) |
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507 | | inr _ ⇒ field_offset_rec id fld' (align pos (alignof t) + sizeof t) |
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508 | ] |
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509 | ]. |
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510 | |
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511 | definition field_offset ≝ λid: ident. λfld: fieldlist. |
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512 | field_offset_rec id fld 0. |
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513 | |
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514 | let rec field_type (id: ident) (fld: fieldlist) on fld : res type := |
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515 | match fld with |
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516 | [ Fnil ⇒ Error ? [MSG UnknownField (*"Unknown field "*); CTX ? id] |
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517 | | Fcons id' t fld' ⇒ match ident_eq id id' with [ inl _ ⇒ OK ? t | inr _ ⇒ field_type id fld'] |
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518 | ]. |
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519 | |
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520 | (* * Some sanity checks about field offsets. First, field offsets are |
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521 | within the range of acceptable offsets. *) |
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522 | (* |
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523 | Remark field_offset_rec_in_range: |
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524 | forall id ofs ty fld pos, |
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525 | field_offset_rec id fld pos = OK ofs → field_type id fld = OK ty → |
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526 | pos <= ofs /\ ofs + sizeof ty <= sizeof_struct fld pos. |
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527 | Proof. |
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528 | intros until ty. induction fld; simpl. |
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529 | congruence. |
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530 | destruct (ident_eq id i); intros. |
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531 | inv H. inv H0. split. apply align_le. apply alignof_pos. apply sizeof_struct_incr. |
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532 | exploit IHfld; eauto. intros [A B]. split; auto. |
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533 | eapply Zle_trans; eauto. apply Zle_trans with (align pos (alignof t)). |
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534 | apply align_le. apply alignof_pos. generalize (sizeof_pos t). omega. |
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535 | Qed. |
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536 | |
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537 | Lemma field_offset_in_range: |
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538 | forall id fld ofs ty, |
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539 | field_offset id fld = OK ofs → field_type id fld = OK ty → |
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540 | 0 <= ofs /\ ofs + sizeof ty <= sizeof_struct fld 0. |
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541 | Proof. |
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542 | intros. eapply field_offset_rec_in_range. unfold field_offset in H; eauto. eauto. |
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543 | Qed. |
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544 | |
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545 | (** Second, two distinct fields do not overlap *) |
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546 | |
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547 | Lemma field_offset_no_overlap: |
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548 | forall id1 ofs1 ty1 id2 ofs2 ty2 fld, |
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549 | field_offset id1 fld = OK ofs1 → field_type id1 fld = OK ty1 → |
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550 | field_offset id2 fld = OK ofs2 → field_type id2 fld = OK ty2 → |
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551 | id1 <> id2 → |
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552 | ofs1 + sizeof ty1 <= ofs2 \/ ofs2 + sizeof ty2 <= ofs1. |
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553 | Proof. |
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554 | intros until ty2. intros fld0 A B C D NEQ. |
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555 | assert (forall fld pos, |
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556 | field_offset_rec id1 fld pos = OK ofs1 -> field_type id1 fld = OK ty1 -> |
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557 | field_offset_rec id2 fld pos = OK ofs2 -> field_type id2 fld = OK ty2 -> |
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558 | ofs1 + sizeof ty1 <= ofs2 \/ ofs2 + sizeof ty2 <= ofs1). |
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559 | induction fld; intro pos; simpl. congruence. |
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560 | destruct (ident_eq id1 i); destruct (ident_eq id2 i). |
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561 | congruence. |
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562 | subst i. intros. inv H; inv H0. |
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563 | exploit field_offset_rec_in_range. eexact H1. eauto. tauto. |
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564 | subst i. intros. inv H1; inv H2. |
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565 | exploit field_offset_rec_in_range. eexact H. eauto. tauto. |
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566 | intros. eapply IHfld; eauto. |
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567 | |
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568 | apply H with fld0 0; auto. |
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569 | Qed. |
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570 | |
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571 | (** Third, if a struct is a prefix of another, the offsets of fields |
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572 | in common is the same. *) |
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573 | |
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574 | Fixpoint fieldlist_app (fld1 fld2: fieldlist) {struct fld1} : fieldlist := |
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575 | match fld1 with |
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576 | | Fnil ⇒ fld2 |
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577 | | Fcons id ty fld ⇒ Fcons id ty (fieldlist_app fld fld2) |
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578 | end. |
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579 | |
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580 | Lemma field_offset_prefix: |
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581 | forall id ofs fld2 fld1, |
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582 | field_offset id fld1 = OK ofs → |
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583 | field_offset id (fieldlist_app fld1 fld2) = OK ofs. |
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584 | Proof. |
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585 | intros until fld2. |
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586 | assert (forall fld1 pos, |
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587 | field_offset_rec id fld1 pos = OK ofs -> |
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588 | field_offset_rec id (fieldlist_app fld1 fld2) pos = OK ofs). |
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589 | induction fld1; intros pos; simpl. congruence. |
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590 | destruct (ident_eq id i); auto. |
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591 | intros. unfold field_offset; auto. |
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592 | Qed. |
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593 | *) |
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594 | |
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595 | |
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596 | (* * Translating Clight types to Cminor types, function signatures, |
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597 | and external functions. *) |
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598 | |
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599 | definition typ_of_type : type → typ ≝ λt. |
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600 | match t with |
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601 | [ Tvoid ⇒ ASTint I32 Unsigned |
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602 | | Tint sz sg ⇒ ASTint sz sg |
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603 | | Tpointer _ ⇒ ASTptr |
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604 | | Tarray _ _ ⇒ ASTptr |
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605 | | Tfunction _ _ ⇒ ASTptr |
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606 | | Tcomp_ptr _ ⇒ ASTptr |
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607 | | _ ⇒ ASTint I32 Unsigned (* structs and unions shouldn't be converted? *) |
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608 | ]. |
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609 | |
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610 | definition opttyp_of_type : type → option typ ≝ λt. |
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611 | match t with |
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612 | [ Tvoid ⇒ None ? |
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613 | | Tint sz sg ⇒ Some ? (ASTint sz sg) |
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614 | | Tpointer _ ⇒ Some ? ASTptr |
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615 | | Tarray _ _ ⇒ Some ? ASTptr |
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616 | | Tfunction _ _ ⇒ Some ? ASTptr |
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617 | | Tcomp_ptr _ ⇒ Some ? ASTptr |
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618 | | _ ⇒ None ? (* structs and unions shouldn't be converted? *) |
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619 | ]. |
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620 | |
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621 | let rec typlist_of_typelist (tl: typelist) : list typ ≝ |
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622 | match tl with |
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623 | [ Tnil ⇒ nil ? |
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624 | | Tcons hd tl ⇒ typ_of_type hd :: typlist_of_typelist tl |
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625 | ]. |
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626 | |
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627 | |
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628 | (* * The [access_mode] function describes how a variable of the given |
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629 | type must be accessed: |
---|
630 | - [By_value ch]: access by value, i.e. by loading from the address |
---|
631 | of the variable using the memory chunk [ch]; |
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632 | - [By_reference]: access by reference, i.e. by just returning |
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633 | the address of the variable; |
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634 | - [By_nothing]: no access is possible, e.g. for the [void] type. |
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635 | |
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636 | We currently do not support 64-bit integers and 128-bit floats, so these |
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637 | have an access mode of [By_nothing]. |
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638 | *) |
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639 | |
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640 | inductive mode: typ → Type[0] ≝ |
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641 | | By_value: ∀t:typ. mode t |
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642 | | By_reference: (*∀r:region.*) mode ASTptr |
---|
643 | | By_nothing: ∀t. mode t. |
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644 | |
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645 | definition access_mode : ∀ty. mode (typ_of_type ty) ≝ λty. |
---|
646 | match ty return λty. mode (typ_of_type ty) with |
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647 | [ Tint i s ⇒ By_value (ASTint i s) |
---|
648 | | Tvoid ⇒ By_nothing … |
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649 | | Tpointer _ ⇒ By_value ASTptr |
---|
650 | | Tarray _ _ ⇒ By_reference |
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651 | | Tfunction _ _ ⇒ By_reference |
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652 | | Tstruct _ fList ⇒ By_nothing … |
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653 | | Tunion _ fList ⇒ By_nothing … |
---|
654 | | Tcomp_ptr _ ⇒ By_value ASTptr |
---|
655 | ]. |
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656 | |
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657 | definition signature_of_type : typelist → type → signature ≝ λargs. λres. |
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658 | mk_signature (typlist_of_typelist args) (opttyp_of_type res). |
---|
659 | |
---|
660 | definition external_function |
---|
661 | : ident → typelist → type → external_function ≝ λid. λtargs. λtres. |
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662 | mk_external_function id (signature_of_type targs tres). |
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