Merge function types in C.

Among other differences, GCC accepts

  typedef int IA[];
  typedef int A10[10];
  static A10 *f(void);
  static IA  *f(void);
  void g(void) {
    (void)sizeof(*f());
  }

but clang used to reject it with:

  invalid application of 'sizeof' to an incomplete type 'IA' (aka 'int []')

The intention of c99's 6.2.7 seems to be that we should use the composite type
and accept as gcc does.

Doing the type merging required some extra fixes:
  * Use the type from the function type in initializations, even if an parameter
    is available.
  * Fix the merging of the noreturn attribute in function types.
  * Make CodeGen  handle the fact that an parameter type can be different from
    the corresponding type in the function type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@168895 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index eb75329461..001a6ac61d 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -2402,6 +2402,12 @@ bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
   if (getLangOpts().CPlusPlus)
     return MergeCXXFunctionDecl(New, Old, S);
 
+  // Merge the function types so the we get the composite types for the return
+  // and argument types.
+  QualType Merged = Context.mergeTypes(Old->getType(), New->getType());
+  if (!Merged.isNull())
+    New->setType(Merged);
+
   return false;
 }