[PATCH v2] Cygwin: spawn: Make ch_spwan_local be initialized properly

[Takashi Yano]

The class child_info_spawn has two constructors: one without arguments
and one with two arguments. The former does not initialize any members.
Commit 1f836c5f7394 used the latter to ensure that the local ch_spawn
(i.e., ch_spawn_local) would be properly initialized. However, this was
insufficient - it initialized only the base child_info members, not the
fields specific to child_info_spawn. This led to the issue reported in
https://cygwin.com/pipermail/cygwin/2025-August/258660.html.

This patch updates the former constructor to properly initialize member
variable 'ev' which was referred without initialization, and switches
ch_spawn_local to use it.

Addresses: https://cygwin.com/pipermail/cygwin/2025-August/258660.html
Fixes: 1f836c5f7394 ("Cygwin: spawn: Make system() thread-safe")
Reported-by: Denis Excoffier <cygwin@Denis-Excoffier.org>
Reviewed-by: Jeremy Drake <cygwin@jdrake.com>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/local_includes/child_info.h | 5 +++--
 winsup/cygwin/spawn.cc                    | 2 +-
 winsup/cygwin/syscalls.cc                 | 2 +-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/local_includes/child_info.h b/winsup/cygwin/local_includes/child_info.h
index 2da62ffaa..b8707b9ec 100644
--- a/winsup/cygwin/local_includes/child_info.h
+++ b/winsup/cygwin/local_includes/child_info.h
@@ -33,7 +33,7 @@ enum child_status
 #define EXEC_MAGIC_SIZE sizeof(child_info)
 
 /* Change this value if you get a message indicating that it is out-of-sync. */
-#define CURR_CHILD_INFO_MAGIC 0xacbf4682U
+#define CURR_CHILD_INFO_MAGIC 0x39f766b5U
 
 #include "pinfo.h"
 struct cchildren
@@ -148,7 +148,8 @@ public:
   char filler[4];
 
   void cleanup ();
-  child_info_spawn () {};
+  child_info_spawn () :
+    child_info (sizeof *this, _CH_NADA, false), ev (NULL) {};
   child_info_spawn (child_info_types, bool);
   void record_children ();
   void reattach_children ();
diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
index 680f0fefd..6cd97ec17 100644
--- a/winsup/cygwin/spawn.cc
+++ b/winsup/cygwin/spawn.cc
@@ -950,7 +950,7 @@ spawnve (int mode, const char *path, const char *const *argv,
   if (!envp)
     envp = empty_env;
 
-  child_info_spawn ch_spawn_local (_CH_NADA, false);
+  child_info_spawn ch_spawn_local;
   switch (_P_MODE (mode))
     {
     case _P_OVERLAY:
diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index 863f8f23c..83a54ca05 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -4535,7 +4535,7 @@ 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. */
-      child_info_spawn ch_spawn_local (_CH_NADA, false);
+      child_info_spawn ch_spawn_local;
       pid_t pid = ch_spawn_local.worker ("/bin/sh", argv, environ, _P_NOWAIT,
 					 __std[0], __std[1]);
 
-- 
2.45.1