[cfe-dev] Generated AST for implicit CXXConstructorDecl

[Mikhail Ramalho via cfe-dev]

I almost forgot:

I know that we can get the VarDecl from the DeclRef (by using getDecl() or
getFoundDecl()). What I meant by "if I can generate the AST with the
varDecls" was actually an AST with the explicit VarDecls of __i0, __i1, etc.

Thank you,


2016-05-10 14:45 GMT+01:00 Mikhail Ramalho <mikhail.ramalho at gmail.com>:

> Hello all,
>
> I'm using libTooling to generate the AST of a given program (that will
> later be translated to our own internal AST), and I just found this odd
> CXXConstructorDecl for the following program:
>
> class X
> {
>   public:
>     X() {};
>
>     char str[20][20][230];
> };
>
> int main(void)
> {
>   X x;
>   X x1 = x;
>   return 0;
> }
>
>
> The implicit constructor for X is:
>
> CXXConstructorDecl 0x3959fd0 <line:3:7> col:7 implicit used X 'void (const
> class X &) throw()' inline
> |   |-ParmVarDecl 0x395a110 <col:7> col:7 used 'const class X &'
> |   |-CXXCtorInitializer Field 0x3908c48 'str' 'char [20][20][230]'
> |   | `-ImplicitCastExpr 0x395a6e8 <col:7> 'char' <LValueToRValue>
> |   |   `-ArraySubscriptExpr 0x395a6c0 <col:7> 'const char' lvalue
> |   |     |-ImplicitCastExpr 0x395a6a8 <col:7> 'const char *'
> <ArrayToPointerDecay>
> |   |     | `-ArraySubscriptExpr 0x395a560 <col:7> 'char const[230]' lvalue
> |   |     |   |-ImplicitCastExpr 0x395a548 <col:7> 'char const (*)[230]'
> <ArrayToPointerDecay>
> |   |     |   | `-ArraySubscriptExpr 0x395a400 <col:7> 'char
> const[20][230]' lvalue
> |   |     |   |   |-ImplicitCastExpr 0x395a3e8 <col:7> 'char const
> (*)[20][230]' <ArrayToPointerDecay>
> |   |     |   |   | `-MemberExpr 0x395a298 <col:7> 'char
> const[20][20][230]' lvalue .str 0x3908c48
> |   |     |   |   |   `-DeclRefExpr 0x395a270 <col:7> 'const class X'
> lvalue ParmVar 0x395a110 '' 'const class X &'
> |   |     |   |   `-ImplicitCastExpr 0x395a368 <col:7> 'unsigned int'
> <LValueToRValue>
> |   |     |   |     `-DeclRefExpr 0x395a340 <col:7> 'unsigned int' lvalue
> Var 0x395a2e0 '__i0' 'unsigned int'
> |   |     |   `-ImplicitCastExpr 0x395a4c0 <col:7> 'unsigned int'
> <LValueToRValue>
> |   |     |     `-DeclRefExpr 0x395a498 <col:7> 'unsigned int' lvalue Var
> 0x395a438 '__i1' 'unsigned int'
> |   |     `-ImplicitCastExpr 0x395a620 <col:7> 'unsigned int'
> <LValueToRValue>
> |   |       `-DeclRefExpr 0x395a5f8 <col:7> 'unsigned int' lvalue Var
> 0x395a598 '__i2' 'unsigned int'
> |   `-CompoundStmt 0x395a748 <col:7>
>
> Which should look this (I think):
>
> X(const X& ref) : str(ref.str[__i0][__i1][__i2]) {}
>
> Or maybe:
>
> X(const X& ref) { str(ref.str[__i0][__i1][__i2]); }
>
> (None of the above is compiled)
> (If we call emit-llvm, it's translated into a memcpy)
>
> Anyway, there are a few things missing on this AST, in my opinion:
>
> 1. No VarDecl for __i0, __i1, __i2.
> 2. No loop to iterate and copy the array elements (a call to memcpy would
> be good as well, but I don't expect that clang will generate that).
>
> Does anyone knows if I can generate the AST with the varDecls and the
> loop? I found a method on SemaDeclCXX that seems to build a loop, it's
> called buildSingleCopyAssignRecursively. It's called
> by buildSingleCopyAssign, that even tries to build a memcpy.
>
> Am I out of luck and will have to go through all the implicit
> generated CXXConstructorDecls and build a loop myself or is there an
> alternative?
>
> Thank you,
>
> --
>
> Mikhail Ramalho.
>



-- 

Mikhail Ramalho.
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