Consider the following -std=c++20:
#include <pthread.h>
constinit pthread_mutex_t foo = PTHREAD_MUTEX_INITIALIZER;
With g++ 12.4.0, this succeeds, but with clang 20.1.6 it fails:
pthreadtest.cpp:3:27: error: variable does not have a constant initializer
3 | constinit pthread_mutex_t foo = PTHREAD_MUTEX_INITIALIZER;
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
pthreadtest.cpp:3:1: note: required by 'constinit' specifier here
3 | constinit pthread_mutex_t foo = PTHREAD_MUTEX_INITIALIZER;
| ^~~~~~~~~
pthreadtest.cpp:3:33: note: cast that performs the conversions of a
reinterpret_cast is not allowed in a constant expression
3 | constinit pthread_mutex_t foo = PTHREAD_MUTEX_INITIALIZER;
| ^
/usr/include/pthread.h:49:35: note: expanded from macro
'PTHREAD_MUTEX_INITIALIZER'
49 | #define PTHREAD_MUTEX_INITIALIZER PTHREAD_NORMAL_MUTEX_INITIALIZER_NP
| ^
/usr/include/pthread.h:47:45: note: expanded from macro
'PTHREAD_NORMAL_MUTEX_INITIALIZER_NP'
47 | #define PTHREAD_NORMAL_MUTEX_INITIALIZER_NP (pthread_mutex_t)19
| ^
1 error generated.
It seems the standard disallows this sort of cast pretty comprehensively.
Is there some way that Cygwin's pthread initializer macros can be made
compatible with constinit?
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