[PATCH v4 3/3] Cygwin: spawn: Make system() thread-safe

[Takashi Yano]

POSIX states system() shall be thread-safe, however, it is not in
current cygwin. This is because ch_spawn is a global and is shared
between threads. With this patch, system() uses ch_spawn_local
instead which is local variable. popen() has the same problem, so
it has been fixed in the same way.

Addresses: https://cygwin.com/pipermail/cygwin/2025-June/258324.html
Fixes: 1fd5e000ace5 ("import winsup-2000-02-17 snapshot")
Reported-by: Takashi Yano <takashi.yano@nifty.ne.jp>
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/spawn.cc    | 3 ++-
 winsup/cygwin/syscalls.cc | 5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
index fd623f4c5..c057f7ebd 100644
--- a/winsup/cygwin/spawn.cc
+++ b/winsup/cygwin/spawn.cc
@@ -950,6 +950,7 @@ spawnve (int mode, const char *path, const char *const *argv,
   if (!envp)
     envp = empty_env;
 
+  child_info_spawn ch_spawn_local;
   switch (_P_MODE (mode))
     {
     case _P_OVERLAY:
@@ -963,7 +964,7 @@ 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);
diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index d6a2c2d3b..83a54ca05 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -4535,8 +4535,9 @@ popen (const char *command, const char *in_type)
       fcntl (stdchild, F_SETFD, stdchild_state | FD_CLOEXEC);
 
       /* Start a shell process to run the given command without forking. */
-      pid_t pid = ch_spawn.worker ("/bin/sh", argv, environ, _P_NOWAIT,
-				   __std[0], __std[1]);
+      child_info_spawn ch_spawn_local;
+      pid_t pid = ch_spawn_local.worker ("/bin/sh", argv, environ, _P_NOWAIT,
+					 __std[0], __std[1]);
 
       /* Reinstate the close-on-exec state */
       fcntl (stdchild, F_SETFD, stdchild_state);
-- 
2.45.1