# HG changeset patch
# User Christian Brabandt <cb@256bit.org>
# Date 1708543802 -3600
# Node ID a400c8f9506f757072f6b8b241454a696e09d382
# Parent  08add78a71b535137bdb5379eb2866a947b1a54f
patch 9.1.0123: MS-Windows: system() may deadlock

Commit: https://github.com/vim/vim/commit/52ecc76c7fa1865603f27bc838efaeaa03cad77c
Author: GuyBrush <miguel.barro@live.com>
Date:   Wed Feb 21 20:16:38 2024 +0100

    patch 9.1.0123: MS-Windows: system() may deadlock

    Problem:  MS-Windows: system() may deadlock when calling binaries that
              expect stdin
    Solution: Ignore the SHELL_EXPAND flag
              (GuyBrush)

    This happens on binaries that expect stdin. For example:

    :echo system("xxd")

    will cause a deadlock.

    SHELL_EXPAND is a flag devoted to support the linux implementation of
    the backtick-expansion mechanism.

    On linux backtic-expansion relies in the function mch_expand_wildchars()
    (os_unix.c) that delegates on each specific shell (bash, sh, csh, zsh)
    the expansion. Basically it composes a shell command that does the
    expansion and redirects the output to a file and call_shell() it. On
    windows backtick-expansion is performed by Vim itself.

    On linux SHELL_EXPAND modifies how mch_call_shell_fork() (os_unix.c)
    works. This function:

    - relies on posix fork() to spawn a child process to execute a
      external command.
    - Child and parent process communicate using pipes (or pseudoterminal
      if available).
      User input (type ahead content) is processed in a loop only if
      !(SHELL_EXPAND || SHELL_COOKED).
      Though signals are used to detect Ctrl-C in all cases (the input
      loop is not necessary to interrupt the function).
      In the backtick-expansion the external command is the shell command
      that provides the expansion. For the child redirection:
      -  SHELL_EXPAND replaces stdin, stdout & stderr to /dev/null. This is
         why the shell command composed includes redirection (otherwise
         output would be lost).

      -  !SHELL_EXPAND replaces stdin, stdout & stderr with the parent
         created pipes (or pseudoterminal).
         Note that the use of SIGINT signal prevents mch_call_shell_fork()
         from hanging vim.

    On Windows mch_system_piped() (os_win32.c) (which is only used when the
    GUI is running) mimics mch_call_shell_fork() (os_unix.c).
    Win32 lacks fork() and relies on CreateProcessW() and only has pipe
    support (not pseudoterminal) which makes the implementation much
    different.

    But, the key idea is that windows lacks signals, the OS provides support
    for console apps but gvim is not one. The only way of detecting a Ctrl-C
    is actually processing user input (type ahead content). By ignoring the
    user input under SHELL_EXPAND the function can hang gvim.

    Ignoring SHELL_EXPAND flag has no consequence in Windows because as
    mentioned above it is only meaningful in linux.

    closes: #13988

    Signed-off-by: GuyBrush <miguel.barro@live.com>
    Signed-off-by: Christian Brabandt <cb@256bit.org>

diff --git a/src/os_win32.c b/src/os_win32.c
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -5155,8 +5155,7 @@ mch_system_piped(char *cmd, int options)
 	    )
 	{
 	    len = 0;
-	    if (!(options & SHELL_EXPAND)
-		&& ((options &
+	    if (((options &
 			(SHELL_READ|SHELL_WRITE|SHELL_COOKED))
 		    != (SHELL_READ|SHELL_WRITE|SHELL_COOKED)
 # ifdef FEAT_GUI
diff --git a/src/version.c b/src/version.c
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    123,
+/**/
     122,
 /**/
     121,