Am 23.01.23 um 18:43 schrieb Jeff Hostetler:

On 1/23/23 11:48 AM, Rose via GitGitGadget wrote:

quoted

From: Seija Kijin <redacted>

Use _beginthreadex instead of CreateThread
since we use the Windows CRT,
as Microsoft recommends _beginthreadex
over CreateThread for these situations.

Finally, check for NULL handles, not "INVALID_HANDLE,"
as _beginthreadex guarantees a valid handle in most cases

Signed-off-by: Seija Kijin <redacted>
---
     win32: fix thread usage for win32
          Use pthread_exit instead of async_exit.
          This means we do not have to deal with Windows's implementation
     requiring an unsigned exit coded despite the POSIX exit code
requiring a
     signed exit code.
          Use _beginthreadex instead of CreateThread since we use the
Windows CRT.
          Finally, check for NULL handles, not "INVALID_HANDLE," as
_beginthreadex
     guarantees a valid handle in most cases
          Signed-off-by: Seija Kijin doremylover123@gmail.com

Published-As:
https://github.com/gitgitgadget/git/releases/tag/pr-git-1440%2FAtariDreams%2FCreateThread-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git
pr-git-1440/AtariDreams/CreateThread-v4
Pull-Request: https://github.com/git/git/pull/1440

Range-diff vs v3:

  1:  68baafba2bd ! 1:  2e2d5ce7745 win32: fix thread usage for win32
      @@ Commit message
                  Signed-off-by: Seija Kijin [off-list ref]
             - ## compat/mingw.c ##
      -@@ compat/mingw.c: static int start_timer_thread(void)
      -     timer_event = CreateEvent(NULL, FALSE, FALSE, NULL);
      -     if (timer_event) {
      -         timer_thread = (HANDLE) _beginthreadex(NULL, 0,
ticktack, NULL, 0, NULL);
      --        if (!timer_thread )
      -+        if (!timer_thread)
      -             return errno = ENOMEM,
      -                 error("cannot start timer thread");
      -     } else
      -
        ## compat/winansi.c ##
       @@ compat/winansi.c: enum {
            TEXT = 0, ESCAPE = 033, BRACKET = '['


  compat/winansi.c | 8 ++++----
  1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/compat/winansi.c b/compat/winansi.c
index 3abe8dd5a27..be65b27bd75 100644
--- a/compat/winansi.c
+++ b/compat/winansi.c

@@ -340,7 +340,7 @@ enum {

      TEXT = 0, ESCAPE = 033, BRACKET = '['
  };
  -static DWORD WINAPI console_thread(LPVOID unused)
+static unsigned int WINAPI console_thread(LPVOID unused)
  {
      unsigned char buffer[BUFFER_SIZE];
      DWORD bytes;

@@ -643,9 +643,9 @@ void winansi_init(void)

          die_lasterr("CreateFile for named pipe failed");
        /* start console spool thread on the pipe's read end */
-    hthread = CreateThread(NULL, 0, console_thread, NULL, 0, NULL);
-    if (hthread == INVALID_HANDLE_VALUE)
-        die_lasterr("CreateThread(console_thread) failed");
+    hthread = (HANDLE)_beginthreadex(NULL, 0, console_thread, NULL,
0, NULL);
+    if (!hthread)
+        die_lasterr("_beginthreadex(console_thread) failed");
        /* schedule cleanup routine */
      if (atexit(winansi_exit))

base-commit: 56c8fb1e95377900ec9d53c07886022af0a5d3c2

This change may or may not be harmless, but it scares me
because it is possibly a very subtle change and is being
made for an unknown reason -- is there a problem being
fixed here?  Or is this just churn for the sake of churn
to avoid an awkward cast of the return code?

What does _beginthreadex() specifically do that we need
it to do for us?

_beginthreadex() does some CRT init and then calls CreateThread(),
so what are we missing by calling CreateThread() directly?

I also question the value of this change. As long as the thread does not
call into any CRT functions, we do not need the services of
_beginthreadex(). AFAICS, it only uses WinAPI functions and some
uncritical C functions like memmove and memset. Am I missing something?

The code in question is 11+ years old and it hasn't been a
problem (right?), so I have to wonder what value do we get
from this change.

The containing function here is setting up a special console
thread and named pipe to access the console, so I doubt that
any of the tests in the test suite actually would actually
exercise this change (since the tests aren't interactive).

The low-level Windows startup code is very tricky and sensitive
(and we need to test with both GCC's CRT and MSVC's CRT).
As I said earlier, the change may or may not be harmless, but
I question the need for it.

Jeff