Add support for GCC's '__auto_type' extension, per the GCC manual:

https://gcc.gnu.org/onlinedocs/gcc/Typeof.html

Differences from the GCC extension:
 * __auto_type is also permitted in C++ (but only in places where
   it could appear in C), allowing its use in headers that might
   be shared across C and C++, or used from C++98
 * __auto_type can be combined with a declarator, as with C++ auto
   (for instance, "__auto_type *p")
 * multiple variables can be declared in a single __auto_type
   declaration, with the C++ semantics (the deduced type must be
   the same in each case)

This patch also adds a missing restriction on applying typeof to
a bit-field, which GCC has historically rejected in C (due to
lack of clarity as to whether the operand should be promoted).
The same restriction also applies to __auto_type in C (in both
GCC and Clang).

This also fixes PR25449.

Patch by Nicholas Allegra!

llvm-svn: 252690

1 files changed, 4 insertions, 2 deletions

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index c3432839c2e..7f2ef495a20 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2653,9 +2653,11 @@ void CXXNameMangler::mangleType(const UnaryTransformType *T) {
 void CXXNameMangler::mangleType(const AutoType *T) {
   QualType D = T->getDeducedType();
   // <builtin-type> ::= Da  # dependent auto
-  if (D.isNull())
+  if (D.isNull()) {
+    assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
+           "shouldn't need to mangle __auto_type!");
     Out << (T->isDecltypeAuto() ? "Dc" : "Da");
-  else
+  } else
     mangleType(D);
 }