Hi Corinna,
On Fri, 19 Jan 2024 15:28:40 +0100
Corinna Vinschen wrote:
> On Jan 19 22:44, Takashi Yano via Cygwin wrote:
> > Hi,
> >
> > I might find the bug of cygwin1.dll (including 3.4.x, 3.5.0 (TEST)).
> > The following test case (c++ code) causes handle leak.
> >
> > This issue is reproducible with both g++ and clang++.
> > However, it does not happen in Linux environment.
> > So I guess this is the cygwin1.dlll bug.
> >
> > I looked into this problem a bit, and found number of event handle
> > increases every loop.
> >
> > I doubt pthread_mutex_xxx functions.
> >
> > #include <future>
> > int func() { return 0; }
> > int main()
> > {
> > for (;;) {
> > std::future<int> f = std::async(std::launch::async, func);
> > f.get();
> > }
> > return 0;
> > }
>
> Can you create a plain C testcase from there? It's much easier to
> debug.
I could symplify the test case:
#include <mutex>
int main()
{
for (;;) {
std::mutex *m = new std::mutex;
m->lock();
m->unlock();
delete m;
}
return 0;
}
And I tried to observe the pthread_mutex_xxx() call. Then found the
test case does like:
#include <pthread.h>
int main()
{
for (;;) {
pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock(&m);
pthread_mutex_unlock(&m);
}
return 0;
}
POSIX states pthread_mutex_t can be initialized with
PTREAD_MUTEX_INITIALZER when it is STATICALLY allocated.
In this case, m is not static. So it seems that this is
a bug of libstdc++. However, the plain c code above works
in Linux without problems even with non-static mutex m.
I guess it is very difficult to make the plain c code above
work in cygwin, because cygwin can not know when cygwin can
discard the mutex resources...
--
Takashi Yano <takashi.y...@nifty.ne.jp>
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