From 265da68fe2c8c48f77b82f736230690870127fa5 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Mon, 9 Jan 2017 21:40:40 +0000
Subject: [PATCH] PR31587: Fix handling of __FUNCSIG__ in C.

Fix crash if __FUNCSIG__ is used in a function without a prototype, and use
"(void)" as parameter list instead of "()" for a function with a no-parameters
prototype, matching MSVC's observed behavior.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291484 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AST/Expr.cpp            |  7 ++++---
 test/CodeGenCXX/funcsig.cpp | 28 +++++++++++++++++++++++-----
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 93f3ad5f2b..edb218871a 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -562,8 +562,7 @@ std::string PredefinedExpr::ComputeName(IdentType IT, const Decl *CurrentDecl) {
       FT = dyn_cast<FunctionProtoType>(AFT);
 
     if (IT == FuncSig) {
-      assert(FT && "We must have a written prototype in this case.");
-      switch (FT->getCallConv()) {
+      switch (AFT->getCallConv()) {
       case CC_C: POut << "__cdecl "; break;
       case CC_X86StdCall: POut << "__stdcall "; break;
       case CC_X86FastCall: POut << "__fastcall "; break;
@@ -583,6 +582,8 @@ std::string PredefinedExpr::ComputeName(IdentType IT, const Decl *CurrentDecl) {
         if (i) POut << ", ";
         POut << Decl->getParamDecl(i)->getType().stream(Policy);
       }
+      if (!Context.getLangOpts().CPlusPlus && !Decl->getNumParams())
+        POut << "void";
 
       if (FT->isVariadic()) {
         if (FD->getNumParams()) POut << ", ";
@@ -592,7 +593,7 @@ std::string PredefinedExpr::ComputeName(IdentType IT, const Decl *CurrentDecl) {
     POut << ")";
 
     if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
-      const FunctionType *FT = MD->getType()->castAs<FunctionType>();
+      assert(FT && "We must have a written prototype in this case.");
       if (FT->isConst())
         POut << " const";
       if (FT->isVolatile())
diff --git a/test/CodeGenCXX/funcsig.cpp b/test/CodeGenCXX/funcsig.cpp
index 2a6e641aec..c064946e92 100644
--- a/test/CodeGenCXX/funcsig.cpp
+++ b/test/CodeGenCXX/funcsig.cpp
@@ -1,22 +1,39 @@
-// RUN: %clang_cc1 -std=c++11 -triple i686-pc-win32 %s -fms-extensions -fno-rtti -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -triple i686-pc-win32 %s -fms-extensions -fno-rtti -emit-llvm -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX
+// RUN: %clang_cc1 -x c -triple i686-pc-win32 %s -fms-extensions -fno-rtti -emit-llvm -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-C
 
 // Similar to predefined-expr.cpp, but not as exhaustive, since it's basically
 // equivalent to __PRETTY_FUNCTION__.
 
-extern "C" int printf(const char *, ...);
+#ifdef __cplusplus
+extern "C"
+#endif
+int printf(const char *, ...);
 
-void freeFunc(int *, char) {
+void funcNoProto() {
+  printf("__FUNCSIG__ %s\n\n", __FUNCSIG__);
+}
+// CHECK-C:   @"\01??_C@_0BL@IHLLLCAO@void?5__cdecl?5funcNoProto?$CI?$CJ?$AA@" = linkonce_odr unnamed_addr constant [27 x i8] c"void __cdecl funcNoProto()\00"
+// CHECK-CXX: @"\01??_C@_0BL@IHLLLCAO@void?5__cdecl?5funcNoProto?$CI?$CJ?$AA@" = linkonce_odr unnamed_addr constant [27 x i8] c"void __cdecl funcNoProto()\00"
+
+void funcNoParams(void) {
+  printf("__FUNCSIG__ %s\n\n", __FUNCSIG__);
+}
+// CHECK-C:   @"\01??_C@_0CA@GBIDFNBN@void?5__cdecl?5funcNoParams?$CIvoid?$CJ?$AA@" = linkonce_odr unnamed_addr constant [32 x i8] c"void __cdecl funcNoParams(void)\00"
+// CHECK-CXX: @"\01??_C@_0BM@GDFBOAEE@void?5__cdecl?5funcNoParams?$CI?$CJ?$AA@" = linkonce_odr unnamed_addr constant [28 x i8] c"void __cdecl funcNoParams()\00"
+
+void freeFunc(int *p, char c) {
   printf("__FUNCSIG__ %s\n\n", __FUNCSIG__);
 }
 // CHECK: @"\01??_C@_0CD@KLGMNNL@void?5__cdecl?5freeFunc?$CIint?5?$CK?0?5cha@" = linkonce_odr unnamed_addr constant [{{.*}} x i8] c"void __cdecl freeFunc(int *, char)\00"
 
+#ifdef __cplusplus
 struct TopLevelClass {
   void topLevelMethod(int *, char);
 };
 void TopLevelClass::topLevelMethod(int *, char) {
   printf("__FUNCSIG__ %s\n\n", __FUNCSIG__);
 }
-// CHECK: @"\01??_C@_0DL@OBHNMDP@void?5__thiscall?5TopLevelClass?3?3t@" = linkonce_odr unnamed_addr constant [{{.*}} x i8] c"void __thiscall TopLevelClass::topLevelMethod(int *, char)\00"
+// CHECK-CXX: @"\01??_C@_0DL@OBHNMDP@void?5__thiscall?5TopLevelClass?3?3t@" = linkonce_odr unnamed_addr constant [{{.*}} x i8] c"void __thiscall TopLevelClass::topLevelMethod(int *, char)\00"
 
 namespace NS {
 struct NamespacedClass {
@@ -25,5 +42,6 @@ struct NamespacedClass {
 void NamespacedClass::namespacedMethod(int *, char) {
   printf("__FUNCSIG__ %s\n\n", __FUNCSIG__);
 }
-// CHECK: @"\01??_C@_0ED@PFDKIEBA@void?5__thiscall?5NS?3?3NamespacedCl@" = linkonce_odr unnamed_addr constant [{{.*}} x i8] c"void __thiscall NS::NamespacedClass::namespacedMethod(int *, char)\00"
+// CHECK-CXX: @"\01??_C@_0ED@PFDKIEBA@void?5__thiscall?5NS?3?3NamespacedCl@" = linkonce_odr unnamed_addr constant [{{.*}} x i8] c"void __thiscall NS::NamespacedClass::namespacedMethod(int *, char)\00"
 }
+#endif
-- 
2.40.0