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, 11 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 8b2e7db8a24..2605acddfac 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3908,7 +3908,7 @@ namespace {
           !Replacement.isNull() && Replacement->isDependentType();
         QualType Result =
           SemaRef.Context.getAutoType(Dependent ? QualType() : Replacement,
-                                      TL.getTypePtr()->isDecltypeAuto(),
+                                      TL.getTypePtr()->getKeyword(),
                                       Dependent);
         AutoTypeLoc NewTL = TLB.push<AutoTypeLoc>(Result);
         NewTL.setNameLoc(TL.getNameLoc());
@@ -3976,6 +3976,11 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result) {
       if (Result.isNull())
         return DAR_FailedAlreadyDiagnosed;
       return DAR_Succeeded;
+    } else if (!getLangOpts().CPlusPlus) {
+      if (isa<InitListExpr>(Init)) {
+        Diag(Init->getLocStart(), diag::err_auto_init_list_from_c);
+        return DAR_FailedAlreadyDiagnosed;
+      }
     }
   }
 
@@ -4013,6 +4018,11 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result) {
         return DAR_Failed;
     }
   } else {
+    if (!getLangOpts().CPlusPlus && Init->refersToBitField()) {
+      Diag(Loc, diag::err_auto_bitfield);
+      return DAR_FailedAlreadyDiagnosed;
+    }
+
     if (AdjustFunctionParmAndArgTypesForDeduction(
             *this, TemplateParamsSt.get(), FuncParam, InitType, Init, TDF))
       return DAR_Failed;