Don't trigger -Wuser-defined-literals for system headers

DimitryAndric · DimitryAndric · commit c7bc461298d5 · 2017-12-14T22:32:24.000Z
Summary: In D41064, I proposed adding `#pragma clang diagnostic ignored "-Wuser-defined-literals"` to some of libc++'s headers, since these warnings are now triggered by clang's new `-std=gnu++14` default: ``` $ cat test.cpp #include <string> $ clang -std=c++14 -Wsystem-headers -Wall -Wextra -c test.cpp In file included from test.cpp:1: In file included from /usr/include/c++/v1/string:470: /usr/include/c++/v1/string_view:763:29: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string_view<char> operator "" sv(const char *__str, size_t __len) ^ /usr/include/c++/v1/string_view:769:32: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string_view<wchar_t> operator "" sv(const wchar_t *__str, size_t __len) ^ /usr/include/c++/v1/string_view:775:33: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string_view<char16_t> operator "" sv(const char16_t *__str, size_t __len) ^ /usr/include/c++/v1/string_view:781:33: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string_view<char32_t> operator "" sv(const char32_t *__str, size_t __len) ^ In file included from test.cpp:1: /usr/include/c++/v1/string:4012:24: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string<char> operator "" s( const char *__str, size_t __len ) ^ /usr/include/c++/v1/string:4018:27: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string<wchar_t> operator "" s( const wchar_t *__str, size_t __len ) ^ /usr/include/c++/v1/string:4024:28: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string<char16_t> operator "" s( const char16_t *__str, size_t __len ) ^ /usr/include/c++/v1/string:4030:28: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals] basic_string<char32_t> operator "" s( const char32_t *__str, size_t __len ) ^ 8 warnings generated. ``` Both @aaron.ballman and @mclow.lists felt that adding this workaround to the libc++ headers was the wrong way, and it should be fixed in clang instead. Here is a proposal to do just that. I verified that this suppresses the warning, even when -Wsystem-headers is used, and that the warning is still emitted for a declaration outside of system headers. Reviewers: aaron.ballman, mclow.lists, rsmith Reviewed By: aaron.ballman Subscribers: mclow.lists, aaron.ballman, andrew, emaste, cfe-commits Differential Revision: https://reviews.llvm.org/D41080 llvm-svn: 320755
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -13076,7 +13076,8 @@ bool Sema::CheckLiteralOperatorDeclaration(FunctionDecl *FnDecl) {
 
   StringRef LiteralName
     = FnDecl->getDeclName().getCXXLiteralIdentifier()->getName();
-  if (LiteralName[0] != '_') {
+  if (LiteralName[0] != '_' &&
+      !getSourceManager().isInSystemHeader(FnDecl->getLocation())) {
     // C++11 [usrlit.suffix]p1:
     //   Literal suffix identifiers that do not start with an underscore
     //   are reserved for future standardization.
diff --git a/clang/test/SemaCXX/no-warn-user-defined-literals-in-system-headers.cpp b/clang/test/SemaCXX/no-warn-user-defined-literals-in-system-headers.cpp
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wsystem-headers -isystem %S %s
+
+#include <no-warn-user-defined-literals-in-system-headers.h>
+
+void operator "" bar(long double); // expected-warning{{user-defined literal suffixes not starting with '_' are reserved}}
diff --git a/clang/test/SemaCXX/no-warn-user-defined-literals-in-system-headers.h b/clang/test/SemaCXX/no-warn-user-defined-literals-in-system-headers.h
@@ -0,0 +1,2 @@
+// Header for no-warn-user-defined-literals-in-system-headers.cpp
+void operator "" foo (const char *);

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+// Header for no-warn-user-defined-literals-in-system-headers.cpp`
	`2`	`+void operator "" foo (const char *);`