Re: [PATCH v4] win32: fix thread usage for win32
From: Jeff Hostetler <hidden>
Date: 2023-01-23 17:44:08
On 1/23/23 11:48 AM, Rose via GitGitGadget wrote:
quoted hunk ↗ jump to hunk
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? 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