r217995 - Instantiate exception specifications when instantiating function types (other

[Alexander Kornienko]

On Thu, Sep 18, 2014 at 1:57 AM, Richard Smith <richard-llvm at metafoo.co.uk>
wrote:

> Author: rsmith
> Date: Wed Sep 17 18:57:05 2014
> New Revision: 217995
>
> URL: http://llvm.org/viewvc/llvm-project?rev=217995&view=rev
> Log:
> Instantiate exception specifications when instantiating function types
> (other
> than the type of a function declaration). We previously didn't instantiate
> these at all! This also covers the pathological case where the only
> mention of
> a parameter pack is within the exception specification; this gives us a
> second
> way (other than alias templates) to reach the horrible state where a type
> contains an unexpanded pack, but its canonical type does not.
>
> Modified:
>     cfe/trunk/include/clang/AST/DataRecursiveASTVisitor.h
>     cfe/trunk/include/clang/AST/Expr.h
>     cfe/trunk/include/clang/AST/RecursiveASTVisitor.h
>     cfe/trunk/include/clang/AST/Type.h
>     cfe/trunk/include/clang/Sema/Sema.h
>     cfe/trunk/lib/AST/Type.cpp
>     cfe/trunk/lib/Sema/SemaDeclCXX.cpp
>     cfe/trunk/lib/Sema/SemaExceptionSpec.cpp
>     cfe/trunk/lib/Sema/SemaTemplateInstantiate.cpp
>     cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
>     cfe/trunk/lib/Sema/SemaType.cpp
>     cfe/trunk/lib/Sema/TreeTransform.h
>     cfe/trunk/test/CXX/except/except.spec/p1.cpp
>     cfe/trunk/test/SemaTemplate/instantiate-exception-spec-cxx11.cpp
>     cfe/trunk/test/SemaTemplate/instantiate-exception-spec.cpp
>
> ...
> Modified: cfe/trunk/lib/AST/Type.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Type.cpp?rev=217995&r1=217994&r2=217995&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/AST/Type.cpp (original)
> +++ cfe/trunk/lib/AST/Type.cpp Wed Sep 17 18:57:05 2014
> @@ -1623,9 +1623,9 @@ FunctionProtoType::FunctionProtoType(Qua
>      QualType *exnSlot = argSlot + NumParams;
>      unsigned I = 0;
>      for (QualType ExceptionType : epi.ExceptionSpec.Exceptions) {
> -      if (ExceptionType->isDependentType())
> -        setDependent();
> -      else if (ExceptionType->isInstantiationDependentType())
> +      // Note that a dependent exception specification does *not* make
> +      // a type dependent; it's not even part of the C++ type system.
> +      if (ExceptionType->isInstantiationDependentType())
>          setInstantiationDependent();
>
>        if (ExceptionType->containsUnexpandedParameterPack())
> @@ -1639,11 +1639,12 @@ FunctionProtoType::FunctionProtoType(Qua
>      *noexSlot = epi.ExceptionSpec.NoexceptExpr;
>
>      if (epi.ExceptionSpec.NoexceptExpr) {
> -      if (epi.ExceptionSpec.NoexceptExpr->isValueDependent()
> -          || epi.ExceptionSpec.NoexceptExpr->isTypeDependent())
> -        setDependent();
> -      else if (epi.ExceptionSpec.NoexceptExpr->isInstantiationDependent())
> +      if (epi.ExceptionSpec.NoexceptExpr->isValueDependent() ||
> +          epi.ExceptionSpec.NoexceptExpr->isInstantiationDependent())
>          setInstantiationDependent();
> +
> +      if
> (epi.ExceptionSpec.NoexceptExpr->containsUnexpandedParameterPack())
> +        setContainsUnexpandedParameterPack();
>      }
>    } else if (getExceptionSpecType() == EST_Uninstantiated) {
>      // Store the function decl from which we will resolve our
> @@ -1669,6 +1670,19 @@ FunctionProtoType::FunctionProtoType(Qua
>    }
>  }
>
> +bool FunctionProtoType::hasDependentExceptionSpec() const {
> +  if (Expr *NE = getNoexceptExpr())
> +    return NE->isValueDependent();
> +  for (unsigned I = 0, N = getNumExceptions(); I != N; ++I)
>

This crashes on test/CXX/except/except.spec/template.cpp in certain build
configurations. I suspect, the reason is the complicated relation between
getNumExceptions/getExceptionType and exception_begin/exception_end:

  exception_iterator exception_end() const {
    if (getExceptionSpecType() != EST_Dynamic)
      return exception_begin();
    return exception_begin() + NumExceptions;
  }
...
  unsigned getNumExceptions() const { return NumExceptions; }
  QualType getExceptionType(unsigned i) const {
    assert(i < NumExceptions && "Invalid exception number!");
    return exception_begin()[i];
  }

I wonder why the two ways to access exceptions are different. It looks like
a bug.

Actually, I don't think we need getNumExceptions/getExceptionType, since
there is ArrayRef<QualType> exceptions();.


> +    // A pack expansion with a non-dependent pattern is still dependent,
> +    // because we don't know whether the pattern is in the exception spec
> +    // or not (that depends on whether the pack has 0 expansions).
> +    if (getExceptionType(I)->isDependentType() ||
> +        getExceptionType(I)->getAs<PackExpansionType>())
> +      return true;
> +  return false;
> +}
> +
>  FunctionProtoType::NoexceptResult
>  FunctionProtoType::getNoexceptSpec(const ASTContext &ctx) const {
>    ExceptionSpecificationType est = getExceptionSpecType();
> ...
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