On 20.03.2025 21:05, Martin Storsjö wrote:
On Thu, 20 Mar 2025, Pali Rohár wrote:
Hello, I started getting new compile warnings during compilation of
mingw-w64 runtime.
In file included from math/modfl.c:6:
.../mingw-w64-headers/crt/fenv.h:64:39: warning: ‘__mingw_fe_dfl_env’
initialized and declared ‘extern’
extern const __MINGW_SELECTANY fenv_t __mingw_fe_dfl_env = { 0, 0 };
^~~~~~~~~~~~~~~~~~
.../mingw-w64-headers/crt/fenv.h:72:39: warning:
‘__mingw_fe_pc64_env’ initialized and declared ‘extern’
extern const __MINGW_SELECTANY fenv_t __mingw_fe_pc64_env = {
0x3f3f003f, 0 };
^~~~~~~~~~~~~~~~~~~
.../mingw-w64-headers/crt/fenv.h:76:39: warning:
‘__mingw_fe_pc53_env’ initialized and declared ‘extern’
extern const __MINGW_SELECTANY fenv_t __mingw_fe_pc53_env = {
0x3f3f103f, 0 };
^~~~~~~~~~~~~~~~~~~
To make this clearer and more actionable, let's repeat a couple
relevant bits of context here:
By default, both GCC and Clang ignore and suppress warnings in files
in what they consider "system header" directories. When most people
build mingw-w64-crt using what would be considered the default way to
build it - by installing mingw-w64-headers into the toolchain's system
header directory, then building mingw-w64-crt so that it finds those
headers implicitly, these warnings are not visible.
Pali builds his mingw-w64-crt in a way that the compiler doesn't
consider mingw-w64-headers as system headers, and thus gets warnings
that nobody else runs into.
Hmm, this is supposed to work with __declspec(selectany). Clang and GCC
for C++ get it right, it's only GCC that complains.
We have more similar declarations with EXTERN_C DECLSPEC_SELECTANY in
headers already, for example DEFINE_GUID. Maybe it would be better to
fix GCC.
Jacek
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