Delay check for prototype on __fastcall functions until after MergeFunctionDecl.

In C, it is only known after merging decls if a function with 0 arguments has
a prototype.  Fixes PR20386, see that for more notes.

llvm-svn: 214408

3 files changed, 27 insertions, 17 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 9ce09288de1..4abbbebf808 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7821,6 +7821,18 @@ bool Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
   }
 
   // Semantic checking for this function declaration (in isolation).
+
+  // Diagnose the use of X86 fastcall on unprototyped functions.
+  QualType NewQType = Context.getCanonicalType(NewFD->getType());
+  const FunctionType *NewType = cast<FunctionType>(NewQType);
+  if (isa<FunctionNoProtoType>(NewType)) {
+    FunctionType::ExtInfo NewTypeInfo = NewType->getExtInfo();
+    if (NewTypeInfo.getCC() == CC_X86FastCall)
+      Diag(NewFD->getLocation(), diag::err_cconv_knr)
+          << FunctionType::getNameForCallConv(CC_X86FastCall);
+    // TODO: Also diagnose unprototyped stdcall functions?
+  }
+
   if (getLangOpts().CPlusPlus) {
     // C++-specific checks.
     if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(NewFD)) {
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 4ad066a7a7a..47df3a69aab 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -4564,23 +4564,12 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state,
     }
   }
 
-  // Diagnose the use of X86 fastcall on unprototyped functions.
-  if (CC == CC_X86FastCall) {
-    if (isa<FunctionNoProtoType>(fn)) {
-      S.Diag(attr.getLoc(), diag::err_cconv_knr)
-        << FunctionType::getNameForCallConv(CC);
-      attr.setInvalid();
-      return true;
-    }
-
-    // Also diagnose fastcall with regparm.
-    if (fn->getHasRegParm()) {
-      S.Diag(attr.getLoc(), diag::err_attributes_are_not_compatible)
-        << "regparm"
-        << FunctionType::getNameForCallConv(CC);
-      attr.setInvalid();
-      return true;
-    }
+  // Also diagnose fastcall with regparm.
+  if (CC == CC_X86FastCall && fn->getHasRegParm()) {
+    S.Diag(attr.getLoc(), diag::err_attributes_are_not_compatible)
+        << "regparm" << FunctionType::getNameForCallConv(CC_X86FastCall);
+    attr.setInvalid();
+    return true;
   }
 
   // Modify the CC from the wrapped function type, wrap it all back, and then
diff --git a/clang/test/Sema/decl-microsoft-call-conv.c b/clang/test/Sema/decl-microsoft-call-conv.c
new file mode 100644
index 00000000000..88a6d920a0a
--- /dev/null
+++ b/clang/test/Sema/decl-microsoft-call-conv.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -triple i686-pc-win32 -verify %s
+
+// It's important that this is a .c file.
+
+// This is fine, as CrcGenerateTable() has a prototype.
+void __fastcall CrcGenerateTable(void);
+void __fastcall CrcGenerateTable() {}
+
+void __fastcall CrcGenerateTableNoProto() {} // expected-error{{function with no prototype cannot use fastcall calling convention}}