Make ASTContext::getDeclAlign return the correct alignment for FunctionDecls

[ahatanak]

Summary

This patch silences an incorrect warning that is issued when a function pointer is cast to another function pointer type. The warning gets issued because alignments of the source and destination do not match in Sema::CheckCastAlign, which happens because ASTContext::getTypeInfoImpl and ASTContext::getDeclAlign return different values for functions (the former returns 4 while the latter returns 1).

[ahatanak]

Call getTypeInfoImpl from getDeclAlign to get the alignment of functions.

[arphaman]

Does this happen with blocks as well?

[ahatanak]

This doesn't happen for objective-c block pointers. Sema::CheckCastAlign returns early when the type isn't a PointerType (BlockPointerType isn't a subclass of PointerType).

[ahatanak]

ping

[ahatanak]

ping

[arphaman]

Thanks. LGTM, I think the patch makes sense.

cfe/trunk/lib/AST/ASTContext.cpp

if (UseAlignAttrOnly) {
     QualType T = VD->getType();
     if (const ReferenceType *RT = T->getAs<ReferenceType>()) {
       if (ForAlignof)
         T = RT->getPointeeType();
       else
         T = getPointerType(RT->getPointeeType());
     }
     QualType BaseT = getBaseElementType(T);
-    if (!BaseT->isIncompleteType() && !T->isFunctionType()) {
+    if (T->isFunctionType())
+      Align = getTypeInfoImpl(T.getTypePtr()).Align;
+    else if (!BaseT->isIncompleteType()) {
       // Adjust alignments of declarations with array type by the
       // large-array alignment on the target.
       if (const ArrayType *arrayType = getAsArrayType(T)) {
         unsigned MinWidth = Target->getLargeArrayMinWidth();
         if (!ForAlignof && MinWidth) {
           if (isa<VariableArrayType>(arrayType))
             Align = std::max(Align, Target->getLargeArrayAlign());
           else if (isa<ConstantArrayType>(arrayType) &&

cfe/trunk/test/Sema/warn-cast-align.c

 };
 
 void test4() {
   struct S s;
   int *i = (int *)s.a;
   i = (int *)&s.s0;
   i = (int *)a;
 }
+
+// No warnings.
+typedef int (*FnTy)(void);
+unsigned int func5(void);
+
+FnTy test5(void) {
+  return (FnTy)&func5;
+}