Make 'align-mismatch' warning work without an associated function declaration

[arphaman]

Summary

This change fixes a crash where a NULL fd was used to emit a diagnostic.
Instead of crashing, just avoid printing the declaration name when there's no
associated function declaration.

The crash was introduced in https://reviews.llvm.org/D97187.

[ravikandhadai]

Looks good to me! Thanks!

clang/include/clang/Basic/DiagnosticSemaKinds.td

 def warn_pointer_indirection_from_incompatible_type : Warning<
   "dereference of type %1 that was reinterpret_cast from type %0 has undefined "
   "behavior">,
   InGroup<UndefinedReinterpretCast>, DefaultIgnore;
 def warn_taking_address_of_packed_member : Warning<
   "taking address of packed member %0 of class or structure %q1 may result in an unaligned pointer value">,
   InGroup<DiagGroup<"address-of-packed-member">>;
 def warn_param_mismatched_alignment : Warning<
-  "passing %0-byte aligned argument to %1-byte aligned parameter %2 of %3 may result in an unaligned pointer access">,
+  "passing %0-byte aligned argument to %1-byte aligned parameter %2%select{| of %4}3 may result in an unaligned pointer access">,
   InGroup<DiagGroup<"align-mismatch">>;
 
 def err_objc_object_assignment : Error<
   "cannot assign to class object (%0 invalid)">;
 def err_typecheck_invalid_operands : Error<
   "invalid operands to binary expression (%0 and %1)">, Deferrable;
 def note_typecheck_invalid_operands_converted : Note<
   "%select{first|second}0 operand was implicitly converted to type %1">;

clang/lib/Sema/SemaChecking.cpp

void Sema::CheckArgAlignment(SourceLocation Loc, NamedDecl *FDecl,
   CharUnits ParamAlign = Context.getTypeAlignInChars(ParamTy);
   CharUnits ArgAlign = Context.getTypeAlignInChars(ArgTy);
 
   // If the argument is less aligned than the parameter, there is a
   // potential alignment issue.
   if (ArgAlign < ParamAlign)
     Diag(Loc, diag::warn_param_mismatched_alignment)
         << (int)ArgAlign.getQuantity() << (int)ParamAlign.getQuantity()
-        << ParamName << FDecl;
+        << ParamName << (FDecl != nullptr) << FDecl;
 }
 
 /// Handles the checks for format strings, non-POD arguments to vararg
 /// functions, NULL arguments passed to non-NULL parameters, and diagnose_if
 /// attributes.
 void Sema::checkCall(NamedDecl *FDecl, const FunctionProtoType *Proto,
                      const Expr *ThisArg, ArrayRef<const Expr *> Args,
                      bool IsMemberFunction, SourceLocation Loc,

clang/test/CodeGen/typedef_alignment_mismatch_warning.cpp

void test10() {
 
   auto *SA8ptr = new StructAligned8(11);
   new (SA8ptr) StructAligned8(12);
   auto *TA4ptr = new TypedefAligned4(11); // expected-warning {{passing 4-byte aligned argument to 8-byte aligned parameter 'this' of 'StructAligned8' may result in an unaligned pointer access}}
   new (TA4ptr) TypedefAligned4(12);       // expected-warning {{passing 4-byte aligned argument to 8-byte aligned parameter 'this' of 'StructAligned8' may result in an unaligned pointer access}}
   auto *UA4ptr = new UsingAligned4(11);
   new (UA4ptr) UsingAligned4(12);
 }
+
+void testFunctionPointerArray(void (*fptr[10])(Aligned8Int *), Aligned2Int* src) {
+  fptr[0](src); // expected-warning {{passing 2-byte aligned argument to 8-byte aligned parameter 1 may result in an unaligned pointer access}}
+}