Hi,
As promised, I am investigating the shared libstdc++ std::thread problem
with winpthreads. Basically, a simple "Hello from thread" test program
throws an "Operation not permitted" std::system_error exception, which is
most likely a result from winpthreads setting errno to EPERM. Test program
below:
#include <iostream>
#include <thread>
using namespace std;
void f()
{
cout << "hello from thread!" << endl;
}
int main()
{
thread t1(f);
thread t2(f);
t1.join();
t2.join();
}
Using any of my std::thread toolchains (4.6.3, 4.6.2-stdthread or
4.7.0-stdthread) you can easily see that when not compiling this with
"-static", the program throws abovementioned exception.
I did some looking into the issue, and came up with the following:
1. There are 16 occurrences of EPERM in winpthreads (although not all are
return codes I think), in pthreads-win32, there are only 6 discernable
usages. This might be due to less correctness in pthreads-win32, but the
difference is at the very least noticeable.
2. I recompiled winpthreads, disabling each EPERM usage on per-file basis,
messing up correct functionality, but hoping to disrupt some pthreads error
to libstdc++ exception conversion, but nothing there had any effect.
3. Due to number 2, I'm now assuming there's some bad code in libstdc++,
resulting in always throwing an exception. Strange enough, Google popped up
this reverse situation for GCC 4.6 and Debian/glibc:
http://stackoverflow.com/questions/7090623/c0x-thread-static-linking-problem
Could it be that in the libstdc++ dll, this function __ghtread_active_p()
is inlined in the dll (so to speak) to always cause this exception being
thrown due to some incompatibility with the assumed semantics of inline and
dll's?
I'd see if building a libstdc++ dll with debug info helps, but frankly, dll
debug info has always been disappointing in comparison to Linux so debug
info.
Any thoughts on how to best proceed are much appreciated.
Ruben
PS: currently winpthreads is broken due to the recent pthread_time.h change:
In file included from
m:\development\mingw64\bin\../lib/gcc/x86_64-w64-mingw32/4.6.3/../../../../x86_64-w64-mingw32/include/time.h:284:0,
from m:/Development/Source/mingw-w64/experimental/winpthreads/src/cond.c:29:
m:/Development/Source/mingw-w64/experimental/winpthreads/include/pthread_time.h:84:28:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'nanosleep'
m:/Development/Source/mingw-w64/experimental/winpthreads/include/pthread_time.h:86:28:
error: expected '=', ',', ';', 'asm' or '__attribute__' before
'clock_nanosleep'
In file included from
m:\development\mingw64\bin\../lib/gcc/x86_64-w64-mingw32/4.6.3/../../../../x86_64-w64-mingw32/include/time.h:284:0,
from m:/Development/Source/mingw-w64/experimental/winpthreads/src/cond.c:29:
m:/Development/Source/mingw-w64/experimental/winpthreads/include/pthread_time.h:87:28:
error: expected '=', ',', ';', 'asm' or '__attribute__' before
'clock_getres'
m:/Development/Source/mingw-w64/experimental/winpthreads/include/pthread_time.h:88:28:
error: expected '=', ',', ';', 'asm' or '__attribute__' before
'clock_gettime'
m:/Development/Source/mingw-w64/experimental/winpthreads/include/pthread_time.h:89:28:
error: expected '=', ',', ';', 'asm' or '__attribute__' before
'clock_settime'
I reincluded <pthread.h> for the time being in that file, working around
this error. I notified Kai of this on IRC, but he hasn't responded yet, so
I'm repeating it here for the record.
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