r188900 - Sema: Use the right type for PredefinedExpr when it's in a lambda.
Richard Smith
richard at metafoo.co.uk
Wed Aug 21 11:33:58 PDT 2013
On Wed, Aug 21, 2013 at 4:45 AM, Benjamin Kramer
<benny.kra at googlemail.com>wrote:
> Author: d0k
> Date: Wed Aug 21 06:45:27 2013
> New Revision: 188900
>
> URL: http://llvm.org/viewvc/llvm-project?rev=188900&view=rev
> Log:
> Sema: Use the right type for PredefinedExpr when it's in a lambda.
>
> 1. We now print the return type of lambdas and return type deduced
> functions
> as "auto". Trailing return types with decltype print the underlying type.
> 2. Use the lambda or block scope for the PredefinedExpr type instead of the
> parent function. This fixes PR16946, a strange mismatch between type of the
> expression and the actual result.
> 3. Verify the type in CodeGen.
> 4. The type for blocks is still wrong. They are numbered and the name is
> not
> known until CodeGen.
>
> Added:
> cfe/trunk/test/SemaCXX/predefined-expr.cpp
> Modified:
> cfe/trunk/lib/AST/Expr.cpp
> cfe/trunk/lib/CodeGen/CGExpr.cpp
> cfe/trunk/lib/Sema/SemaExpr.cpp
>
> Modified: cfe/trunk/lib/AST/Expr.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=188900&r1=188899&r2=188900&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/AST/Expr.cpp (original)
> +++ cfe/trunk/lib/AST/Expr.cpp Wed Aug 21 06:45:27 2013
> @@ -585,7 +585,18 @@ std::string PredefinedExpr::ComputeName(
>
> POut.flush();
>
> - if (!isa<CXXConstructorDecl>(FD) && !isa<CXXDestructorDecl>(FD))
> + // Print "auto" for all deduced return types. This includes C++1y
> return
> + // type deduction and lambdas. For trailing return types resolve the
> + // decltype expression. Otherwise print the real type when this is
> + // not a constructor or destructor.
> + if ((isa<CXXMethodDecl>(FD) &&
> + cast<CXXMethodDecl>(FD)->getParent()->isLambda()) ||
> + (FT && FT->getResultType()->getAs<AutoType>()))
> + Proto = "auto " + Proto;
>
This looks wrong in a couple of ways:
* For a lambda with an explicitly-specified return type, we'll print
'auto' anyway
* For a function with a return type of, say, "auto *", we'll not hit this
special case
Instead, you should use the declared return type (the type as written, from
the TypeSourceInfo). It looks like we'll unhelpfully put 'DependentTy'
there if no return type is specified; perhaps we should put an undeduced
'auto' type there instead.
> + else if (FT && FT->getResultType()->getAs<DecltypeType>())
> + FT->getResultType()->getAs<DecltypeType>()->getUnderlyingType()
> + .getAsStringInternal(Proto, Policy);
>
Why perform this partial desugaring?
> + else if (!isa<CXXConstructorDecl>(FD) && !isa<CXXDestructorDecl>(FD))
>
What about conversion operators? They also have no declared return type.
(And 'operator auto()' in C++14 is another case we need to handle
carefully.)
> AFT->getResultType().getAsStringInternal(Proto, Policy);
>
> Out << Proto;
>
> Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=188900&r1=188899&r2=188900&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGExpr.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGExpr.cpp Wed Aug 21 06:45:27 2013
> @@ -1937,7 +1937,7 @@ LValue CodeGenFunction::EmitPredefinedLV
> case PredefinedExpr::Function:
> case PredefinedExpr::LFunction:
> case PredefinedExpr::PrettyFunction: {
> - unsigned IdentType = E->getIdentType();
> + PredefinedExpr::IdentType IdentType = E->getIdentType();
> std::string GlobalVarName;
>
> switch (IdentType) {
> @@ -1961,17 +1961,24 @@ LValue CodeGenFunction::EmitPredefinedLV
> FnName = FnName.substr(1);
> GlobalVarName += FnName;
>
> + // If this is outside of a function use the top level decl.
> const Decl *CurDecl = CurCodeDecl;
> - if (CurDecl == 0)
> + if (CurDecl == 0 || isa<VarDecl>(CurDecl))
> CurDecl = getContext().getTranslationUnitDecl();
>
> - std::string FunctionName =
> - (isa<BlockDecl>(CurDecl)
> - ? FnName.str()
> - :
> PredefinedExpr::ComputeName((PredefinedExpr::IdentType)IdentType,
> - CurDecl));
> + const Type *ElemType = E->getType()->getArrayElementTypeNoTypeQual();
> + std::string FunctionName;
> + if (isa<BlockDecl>(CurDecl)) {
> + // Blocks use the mangled function name.
> + // FIXME: ComputeName should handle blocks.
> + FunctionName = FnName.str();
> + } else {
> + FunctionName = PredefinedExpr::ComputeName(IdentType, CurDecl);
> + assert(cast<ConstantArrayType>(E->getType())->getSize() - 1 ==
> + FunctionName.size() &&
> + "Computed __func__ length differs from type!");
> + }
>
> - const Type* ElemType = E->getType()->getArrayElementTypeNoTypeQual();
> llvm::Constant *C;
> if (ElemType->isWideCharType()) {
> SmallString<32> RawChars;
>
> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=188900&r1=188899&r2=188900&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Wed Aug 21 06:45:27 2013
> @@ -2759,14 +2759,14 @@ ExprResult Sema::ActOnPredefinedExpr(Sou
> // Pre-defined identifiers are of type char[x], where x is the length
> of the
> // string.
>
> - Decl *currentDecl = getCurFunctionOrMethodDecl();
> - // Blocks and lambdas can occur at global scope. Don't emit a warning.
> - if (!currentDecl) {
> - if (const BlockScopeInfo *BSI = getCurBlock())
> - currentDecl = BSI->TheDecl;
> - else if (const LambdaScopeInfo *LSI = getCurLambda())
> - currentDecl = LSI->CallOperator;
> - }
> + // Pick the current block, lambda or function.
> + Decl *currentDecl;
> + if (const BlockScopeInfo *BSI = getCurBlock())
> + currentDecl = BSI->TheDecl;
> + else if (const LambdaScopeInfo *LSI = getCurLambda())
> + currentDecl = LSI->CallOperator;
> + else
> + currentDecl = getCurFunctionOrMethodDecl();
>
I don't think this correctly handles the case where FunctionScopes.back()
is an SK_CapturedRegion (inside, say, a lambda).
>
> if (!currentDecl) {
> Diag(Loc, diag::ext_predef_outside_function);
>
> Added: cfe/trunk/test/SemaCXX/predefined-expr.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/predefined-expr.cpp?rev=188900&view=auto
>
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/predefined-expr.cpp (added)
> +++ cfe/trunk/test/SemaCXX/predefined-expr.cpp Wed Aug 21 06:45:27 2013
> @@ -0,0 +1,40 @@
> +// RUN: %clang_cc1 -std=c++1y -fblocks -fsyntax-only -verify %s
> +// PR16946
> +// expected-no-diagnostics
> +
> +auto foo() {
> + static_assert(sizeof(__func__) == 4, "foo");
> + static_assert(sizeof(__FUNCTION__) == 4, "foo");
> + static_assert(sizeof(__PRETTY_FUNCTION__) == 11, "auto foo()");
> + return 0;
> +}
> +
> +auto bar() -> decltype(42) {
> + static_assert(sizeof(__func__) == 4, "bar");
> + static_assert(sizeof(__FUNCTION__) == 4, "bar");
> + static_assert(sizeof(__PRETTY_FUNCTION__) == 10, "int bar()");
> + return 0;
> +}
> +
> +int main() {
> + static_assert(sizeof(__func__) == 5, "main");
> + static_assert(sizeof(__FUNCTION__) == 5, "main");
> + static_assert(sizeof(__PRETTY_FUNCTION__) == 11, "int main()");
> +
> + []() {
> + static_assert(sizeof(__func__) == 11, "operator()");
> + static_assert(sizeof(__FUNCTION__) == 11, "operator()");
> + static_assert(sizeof(__PRETTY_FUNCTION__) == 51,
> + "auto main()::<anonymous class>::operator()() const");
> + return 0;
> + }
> + ();
> +
> + ^{
> + // FIXME: This is obviously wrong.
> + static_assert(sizeof(__func__) == 1, "__main_block_invoke");
> + static_assert(sizeof(__FUNCTION__) == 1, "__main_block_invoke");
> + static_assert(sizeof(__PRETTY_FUNCTION__) == 1,
> "__main_block_invoke");
> + }
> + ();
> +}
>
>
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