[cfe-dev] Template specialization: why drop attributes?

[Sharlet, Dillon]

Hello,

I am working on a custom attribute for an experimental project. I've just finally tracked down a problem where explicit template specializations have their attributes removed by Clang. I'm suspicious of the following function:

/// \brief Strips various properties off an implicit instantiation
/// that has just been explicitly specialized.
static void StripImplicitInstantiation(NamedDecl *D) {
  // FIXME: "make check" is clean if the call to dropAttrs() is commented out.
  D->dropAttrs();

  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    FD->setInlineSpecified(false);
  }
}

'dropAttrs' does exactly what you would expect: it removes the attributes from my explicit specialization. To me, this seems like incorrect behavior. Consider the following program:

template < int N >
int Test(int x) __attribute__((custom))
{
       return x * N;
}

template < >
int Test < 1 > (int x) __attribute__((custom))
{
       return x;
}

When I debug a call to Test < 1 >, it behaves as if the program was written like so:

template < int N >
int Test(int x) __attribute__((custom))
{
       return x * N;
}

template < >
int Test < 1 > (int x) // custom attribute removed by StripImplicitInstantiation.
{
       return x;
}

I was hoping to understand the reasoning for this before I commented out dropAttrs here. The comment above dropAttrs seems to imply that it might not be fully correct. What is "make check"?

Thank you for any insight into this issue!


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