2.2  Chaîne de compilation 2/5

• Production du code intermédiaire par :
  • expansion des macros ;
  • expansion des fichiers d’entêtes ;

    $ gcc -E  prog.c -o prog-cpp.c
    $ cat prog-cpp.c 
    # 1 "prog.c"
    ...
    # 319 "/usr/include/stdio.h"
    ...
    extern int printf (const char *__restrict __format, ...);
    ...
    # 2 "prog.c" 2
    int main(void){
    int i;
    i=0;
    for(i=1;i<=10;i++) printf("%d\n",i);
    return 0;
    }
    

  • création d’un arbre syntaxique abstrait (AST) ;
  • options pour obtenir l’arbre gcc --dump-tree-xxx ;

    $ gcc -Wall --dump-tree-original-raw prog.c
    $ ./ast2dot.rb prog.c.003t.original > prog-original.dot
    $ dot -Tpng prog-original.dot > prog-original.png
    

    
    Image originale : prog-ast-full.png
  • exercice : retrouvez les deux initialisations de i ;
  • avec un compilateur différent : clang -Xclang -ast-dump -fsyntax-only ;

    TranslationUnitDecl 0x9bcb300 <<invalid sloc>> <invalid sloc>
    |-TypedefDecl 0x9bcb5d0 <<invalid sloc>> <invalid sloc> implicit __builtin_va_list 'char *'
    |-FunctionDecl 0x9bcb6c0 <prog.c:1:12> col:12 implicit referenced printf 'int (const char *, ...)' extern
    | |-ParmVarDecl 0x9bcb720 <<invalid sloc>> <invalid sloc> 'const char *'
    | `-FormatAttr 0x9bcb760 <col:12> Implicit printf 1 2
    |-FunctionDecl 0x9bcb7a0 prev 0x9bcb6c0 <col:1, col:56> col:12 used printf 'int (const char *, ...)' extern
    | |-ParmVarDecl 0x9bcb630 <col:20, col:43> col:43 __format 'const char *restrict'
    | `-FormatAttr 0x9bcb820 <col:12> Inherited printf 1 2
    `-FunctionDecl 0x9bcb8c0 <line:5:1, line:10:1> line:5:5 main 'int (void)'
      `-CompoundStmt 0x9bcbbf0 <col:15, line:10:1>
        |-DeclStmt 0x9bcb980 <line:6:1, col:6>
        | `-VarDecl 0x9bcb950 <col:1, col:5> col:5 used i 'int'
        |-BinaryOperator 0x9bcb9c0 <line:7:1, col:3> 'int' '='
        | |-DeclRefExpr 0x9bcb990 <col:1> 'int' lvalue Var 0x9bcb950 'i' 'int'
        | `-IntegerLiteral 0x9bcb9a8 <col:3> 'int' 0
        |-ForStmt 0x9bcbba0 <line:8:1, line:4:41>
        | |-BinaryOperator 0x9bcba08 <line:8:5, col:7> 'int' '='
        | | |-DeclRefExpr 0x9bcb9d8 <col:5> 'int' lvalue Var 0x9bcb950 'i' 'int'
        | | `-IntegerLiteral 0x9bcb9f0 <col:7> 'int' 1
        | |-<<<NULL>>>
        | |-BinaryOperator 0x9bcba60 <col:9, line:2:13> 'int' '<='
        | | |-ImplicitCastExpr 0x9bcba50 <line:8:9> 'int' <LValueToRValue>
        | | | `-DeclRefExpr 0x9bcba20 <col:9> 'int' lvalue Var 0x9bcb950 'i' 'int'
        | | `-IntegerLiteral 0x9bcba38 <line:2:13> 'int' 10
        | |-UnaryOperator 0x9bcba90 <line:8:16, col:17> 'int' postfix '++'
        | | `-DeclRefExpr 0x9bcba78 <col:16> 'int' lvalue Var 0x9bcb950 'i' 'int'
        | `-CallExpr 0x9bcbb48 <line:4:26, col:41> 'int'
        |   |-ImplicitCastExpr 0x9bcbb38 <col:26> 'int (*)(const char *, ...)' <FunctionToPointerDecay>
        |   | `-DeclRefExpr 0x9bcbaa4 <col:26> 'int (const char *, ...)' Function 0x9bcb7a0 'printf' 'int (const char *, ...)'
        |   |-ImplicitCastExpr 0x9bcbb80 <col:33> 'const char *' <BitCast>
        |   | `-ImplicitCastExpr 0x9bcbb70 <col:33> 'char *' <ArrayToPointerDecay>
        |   |   `-StringLiteral 0x9bcbae0 <col:33> 'char [4]' lvalue "%d\n"
        |   `-ImplicitCastExpr 0x9bcbb90 <line:8:35> 'int' <LValueToRValue>
        |     `-DeclRefExpr 0x9bcbb04 <col:35> 'int' lvalue Var 0x9bcb950 'i' 'int'
        `-ReturnStmt 0x9bcbbe0 <line:9:1, line:3:18>
          `-IntegerLiteral 0x9bcbbc8 <col:18> 'int' 0
    

  • même exercice.