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Date: Wed, 16 Jul 2025 23:52:36 +0900
To: cygwin AT cygwin DOT com
Subject: Re: Calling system() in multi-threads.
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From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
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Hi Corinna,

On Wed, 18 Jun 2025 20:31:27 +0900
Takashi Yano wrote:
> On Tue, 17 Jun 2025 15:42:26 -0700
> Mark Geisert wrote:
> > Hi Takashi,
> > 
> > On 6/17/2025 5:54 AM, Takashi Yano via Cygwin wrote:
> > > Hi,
> > > 
> > > If system() is called in parallel in threads, system()
> > > fails with exit code 127.
> > > 
> > > Just compile pthread_system.c attached and run.
> > > 
> > > I believe system() is multi-thread safe so the STC
> > > should work.
> > 
> > I regret to inform that system() is not currently MT-safe.  I discovered 
> > this a few years ago when porting YAFU (Yet Another Factoring Utility).
> > 
> > I ended up supplying a wrapper that serialized the system() call itself 
> > but allowed multiple wrappers (and thus child processes) to be running 
> > at the same time.  I never got around to supplying a fix for Cygwin. 
> > I've attached the code.
> > HTH somehow,
> 
> Thanks for the information. I guess the cause is that accessing
> child_info_spawn NO_COPY ch_spawn;
> in spwan.cc conflicts with other threads. I wonder ch_spawn should
> be thread-specific. Or should be guarded by lock.

Do you have any idea?

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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