[cfe-dev] llvm::FoldingSetNodeID to compare Stmt

[Pedro Delgado Perez]

Wow, so simple... That function mixed me up as it said "it[rsquo]s not as trivial to test if two expressions are the same", but it should say "equivalent" instead of "same".

You really helped me. Thanks a lot Richard!

Pedro.


El día 22 ene 2014 01:22, Richard Smith <metafoo at gmail.com> escribió:
> On Sat Jan 18 2014 at 4:23:08 AM, Pedro Delgado Perez <pedro.delgadoperez at mail.uca.es [ mailto:pedro.delgadoperez at mail.uca.es ]> wrote:
> 
> Hi,
> 
> Up to now, to determine if two objects "Stmt" were the same, I have been using the function "areSameExpr", which appers at the end of this link:
> 
> http://clang.llvm.org/docs/LibASTMatchersTutorial.html [ http://clang.llvm.org/docs/LibASTMatchersTutorial.html ]
> static bool areSameExpr(ASTContext *Context, const Expr *First,                        const Expr *Second) {  if (!First || !Second)    return false;  llvm::FoldingSetNodeID FirstID, SecondID;  First->Profile(FirstID, *Context, true);  Second->Profile(SecondID, *Context, true);  return FirstID == SecondID;}
> However, I have a problem with that function. To illustrate the issue, I retrieve a concrete Stmt (in bold in the example below) in a CompoundStmt through a matcher:
> 
> {
> A::getca();
> m();
> A::getca(); 
> int l = 1; 
> }
> 
> Then, when handling that Stmt, I search for the position of that stmt within the compoundStmt with a simple loop and using the function "areSameExpr" aforementioned.
> 
> for(CompoundStmt::body_iterator st = CompStmt->body_begin(); st != CompStmt->body_end(); st++){ 
>                 
>                if(areSameStmt(Context, *st, StmtBound)){
>                    ....
>                   }
> }
> 
> However, this function considers that the first stmt in the compoundStmt is the same as the third one, and that is a problem in my case because I need to determine every stmt as unique to know the position. 
> I have been studying the class llvm::FoldingSetNodeID
> http://llvm.org/docs/doxygen/html/classllvm_1_1FoldingSetNodeID.html#a66f5b8a0b6a74b310d856ca736c1eb8c [ http://llvm.org/docs/doxygen/html/classllvm_1_1FoldingSetNodeID.html#a66f5b8a0b6a74b310d856ca736c1eb8c ]
> 
> I tried to use the method "ComputeHash" to compare both stmt, but it didn't suppose any change.
> 
> Please, does anyone know how I could fix this?
> 
If you want to check if you have the same Stmt, just compare the Stmt*. The Profile mechanism is intended to allow you to determine if two Stmts are equivalent.

Thanks,

Pedro.
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