Author: aaronballman
Date: Thu Sep 15 13:07:51 2016
New Revision: 281632
URL: http://llvm.org/viewvc/llvm-project?rev=281632&view=rev
Log:
Reapply: Silence false positive diagnostics regarding passing an object of
enumeration type to va_start().
The underlying type for an enumeration in C is either char, signed int, or
unsigned int. In the case the underlying type is chosen to be char (such as
when passing -fshort-enums or using __attribute__((packed)) on the enum
declaration), the enumeration can result in undefined behavior. However, when
the underlying type is signed int or unsigned int (or long long as an
extension), there is no undefined behavior because the types are compatible.
This patch silences diagnostics for the latter while retaining the diagnostics
for the former.
This patch addresses PR29140.
Modified:
cfe/trunk/lib/Sema/SemaChecking.cpp
cfe/trunk/test/Sema/varargs.c
Modified: cfe/trunk/lib/Sema/SemaChecking.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=281632&r1=281631&r2=281632&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaChecking.cpp (original)
+++ cfe/trunk/lib/Sema/SemaChecking.cpp Thu Sep 15 13:07:51 2016
@@ -3240,8 +3240,17 @@ bool Sema::SemaBuiltinVAStartImpl(CallEx
Diag(TheCall->getArg(1)->getLocStart(),
diag::warn_second_arg_of_va_start_not_last_named_param);
else if (IsCRegister || Type->isReferenceType() ||
- Type->isPromotableIntegerType() ||
- Type->isSpecificBuiltinType(BuiltinType::Float)) {
+ Type->isSpecificBuiltinType(BuiltinType::Float) || [=] {
+ // Promotable integers are UB, but enumerations need a bit of
+ // extra checking to see what their promotable type actually is.
+ if (!Type->isPromotableIntegerType())
+ return false;
+ if (!Type->isEnumeralType())
+ return true;
+ const EnumDecl *ED = Type->getAs<EnumType>()->getDecl();
+ return !(ED &&
+ Context.typesAreCompatible(ED->getPromotionType(),
Type));
+ }()) {
unsigned Reason = 0;
if (Type->isReferenceType()) Reason = 1;
else if (IsCRegister) Reason = 2;
Modified: cfe/trunk/test/Sema/varargs.c
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/varargs.c?rev=281632&r1=281631&r2=281632&view=diff
==============================================================================
--- cfe/trunk/test/Sema/varargs.c (original)
+++ cfe/trunk/test/Sema/varargs.c Thu Sep 15 13:07:51 2016
@@ -1,5 +1,6 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify %s -triple i386-pc-unknown
// RUN: %clang_cc1 -fsyntax-only -verify %s -triple x86_64-apple-darwin9
+// RUN: %clang_cc1 -fsyntax-only -fms-compatibility -DMS -verify %s -triple
x86_64-pc-win32
void f1(int a)
{
@@ -94,3 +95,20 @@ void f12(register int i, ...) { // expe
__builtin_va_start(ap, i); // expected-warning {{passing a parameter
declared with the 'register' keyword to 'va_start' has undefined behavior}}
__builtin_va_end(ap);
}
+
+enum __attribute__((packed)) E1 {
+ one1
+};
+
+void f13(enum E1 e, ...) {
+ __builtin_va_list va;
+ __builtin_va_start(va, e);
+#ifndef MS
+ // In Microsoft compatibility mode, all enum types are int, but in
+ // non-ms-compatibility mode, this enumeration type will undergo default
+ // argument promotions.
+ // expected-note@-7 {{parameter of type 'enum E1' is declared here}}
+ // expected-warning@-6 {{passing an object that undergoes default argument
promotion to 'va_start' has undefined behavior}}
+#endif
+ __builtin_va_end(va);
+}
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