Paul Eggert wrote:
> Where it’s easy, prefer ‘static_assert’ to ‘verify’,
Compiling a current GNU gettext with MSVC 14, I get this compilation error:
libtool: compile: /home/bruno/msvc/compile cl -nologo -DIN_LIBASPRINTF
-DHAVE_CONFIG_H -D__USE_MINGW_ANSI_STDIO=0 -I.
-I../../../gettext-runtime/libasprintf -Ignulib-lib
-I../../../gettext-runtime/libasprintf/gnulib-lib
-D_WIN32_WINNT=_WIN32_WINNT_WIN7 -I/usr/local/msvc64/include -MD -c
../../../gettext-runtime/libasprintf/autosprintf.cc -o autosprintf.obj
autosprintf.cc
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\xstddef(376):
error C2720: 'std::hash<_Kty>::_gl_static_assert_function3': 'extern'
storage-class specifier illegal on members
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\xstddef(378):
note: see reference to class template instantiation 'std::hash<_Kty>' being
compiled
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(744): error C2720:
'std::_Change_sign<_Ty>::_gl_static_assert_function4': 'extern' storage-class
specifier illegal on members
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(777): note: see reference to class template
instantiation 'std::_Change_sign<_Ty>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(1193): error C2720:
'std::integer_sequence<_Ty,_Vals...>::_gl_static_assert_function5': 'extern'
storage-class specifier illegal on members
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(1203): note: see reference to class template
instantiation 'std::integer_sequence<_Ty,_Vals...>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(1502): error C2720:
'std::result_of<_Fty>::_gl_static_assert_function7': 'extern' storage-class
specifier illegal on members
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(1505): note: see reference to class template
instantiation 'std::result_of<_Fty>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(1580): error C2720:
'std::reference_wrapper<_Ty>::_gl_static_assert_function8': 'extern'
storage-class specifier illegal on members
C:\Program Files (x86)\Microsoft Visual Studio
14.0\VC\include\type_traits(1612): note: see reference to class template
instantiation 'std::reference_wrapper<_Ty>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(423):
error C2720:
'std::tuple_element<_Idx,std::array<_Ty,_Size>>::_gl_static_assert_function9':
'extern' storage-class specifier illegal on members
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(426):
note: see reference to class template instantiation
'std::tuple_element<_Idx,std::array<_Ty,_Size>>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(445):
error C2059: syntax error: ')'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(447):
note: see reference to class template instantiation
'std::tuple_element<_Index,std::tuple<>>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(445):
error C2947: expecting '>' to terminate template-argument-list, found '>'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(445):
error C2976: 'std::integral_constant': too few template arguments
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\xtr1common(23):
note: see declaration of 'std::integral_constant'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(447):
error C2143: syntax error: missing ';' before '}'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\utility(447):
fatal error C1004: unexpected end-of-file found
make[4]: *** [Makefile:1412: autosprintf.lo] Error 1
The situation with this compiler (in C++ mode) is:
- It supports 'static_assert' with 2 arguments.
- It does not support 'static_assert' with 1 argument.
- Its header files make use of the 'static_assert' with 2 arguments,
for example:
template<size_t _Index>
struct tuple_element<_Index, tuple<> >
{ // enforce bounds checking
static_assert(_Always_false<integral_constant<size_t, _Index> >::value,
"tuple index out of bounds");
};
Thus, our existing definition of static_assert via _Static_assert an _GL_VERIFY
does not work, because 'extern' is not allowed inside a struct/class definition.
This attempted patch
diff --git a/lib/verify.h b/lib/verify.h
index a0d597f3d4..608c9bda20 100644
--- a/lib/verify.h
+++ b/lib/verify.h
@@ -229,7 +229,13 @@ template <int w>
# if (!defined static_assert \
&& __STDC_VERSION__ < 202311 \
&& __cpp_static_assert < 201411 && __GNUG__ < 6)
-# define static_assert _Static_assert /* C11 requires this #define. */
+# if defined __cplusplus && _MSC_VER >= 1900
+/* MSVC 14 in C++ mode supports the 2-arguments static_assert but not the
+ one-argument static_assert, and it does not support _Static_assert. */
+# define static_assert(R, ...) static_assert((R), "static assertion failed")
+# else
+# define static_assert _Static_assert /* C11 requires this #define. */
+# endif
# endif
#endif
does not work either, because when we define static_assert as a macro, it
parses
static_assert(_Always_false<integral_constant<size_t, _Index> >::value,
"tuple index out of bounds");
as a macro call with 3 arguments:
argument 1: _Always_false<integral_constant<size_t
argument 2: _Index> >::value
argument 3: "tuple index out of bounds"
Any ideas how to get this working?
Bruno
