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Date: Fri, 18 Jul 2025 16:25:49 +0200
To: cygwin AT cygwin DOT com
Subject: Re: Calling system() in multi-threads.
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From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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On Jul 18 22:32, Takashi Yano via Cygwin wrote:
> I embedded debug code into mm/cygheap.cc, that is:
> 
> diff --git a/winsup/cygwin/mm/cygheap.cc b/winsup/cygwin/mm/cygheap.cc
> index 338886468..bab4067e0 100644
> --- a/winsup/cygwin/mm/cygheap.cc
> +++ b/winsup/cygwin/mm/cygheap.cc
> @@ -371,7 +371,16 @@ _cmalloc (unsigned size)
>    if (cygheap->buckets[b])
>      {
>        rvc = (_cmalloc_entry *) cygheap->buckets[b];
> -      cygheap->buckets[b] = rvc->ptr;
> +      __try
> +	{
> +	  cygheap->buckets[b] = rvc->ptr;
> +	}
> +      __except (NO_ERROR)
> +	{ /* Shouldl not reach */
> +	  system_printf("b = %d", b);
> +	  assert (false);
> +	}
> +      __endtry
>        rvc->b = b;
>      }
>    else
> diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
> index cb58b6eed..32f6bdead 100644
> --- a/winsup/cygwin/spawn.cc
> +++ b/winsup/cygwin/spawn.cc
> @@ -944,6 +944,7 @@ spawnve (int mode, const char *path, const char *const *argv,
>    int ret;
>  
>    syscall_printf ("spawnve (%s, %s, %p)", path, argv[0], envp);
> +  child_info_spawn ch_spawn_local;
>  
>    if (!envp)
>      envp = empty_env;
> @@ -961,7 +962,7 @@ spawnve (int mode, const char *path, const char *const *argv,
>      case _P_WAIT:
>      case _P_DETACH:
>      case _P_SYSTEM:
> -      ret = ch_spawn.worker (path, argv, envp, mode);
> +      ret = ch_spawn_local.worker (path, argv, envp, mode);
>        break;
>      default:
>        set_errno (EINVAL);
> 
> The result is like this! Why???
> 
>       0 [main] sh 617 _cmalloc: b = 1
> assertion "false" failed: file "../../.././winsup/cygwin/mm/cygheap.cc", line 381, function: void* _cmalloc(unsigned int)

I don't know.  Looks like rvc points into nirvana.  Who's the caller?
what's the value of cygheap->buckets[1]?  Is something filling up cygheap
fast, perhaps?  


Corinna

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