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SDL_SemWaitTimeout returns -1 and sets error instead of SDL_MUTEX_TIMEDOUT on time out #665

SDLBugzilla opened this issue Feb 10, 2021 · 0 comments


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@SDLBugzilla SDLBugzilla commented Feb 10, 2021

This bug report was migrated from our old Bugzilla tracker.

These attachments are available in the static archive:

Reported in version: 1.2.15
Reported for operating system, platform: Linux, x86

Comments on the original bug report:

On 2012-02-19 19:01:08 +0000, wrote:

Created attachment 824
Fix to treat ETIMEDOUT as a time out instead of an error (and update the test)

Using SDL 1.2.15 on Linux, SDL_SemWaitTimeout appears to return -1 when I was expecting SDL_MUTEX_TIMEDOUT. I don't see this issue on 1.2.14.

According to the documentation for SDL_SemWaitTimeout, it should return 0 if successfully locked, SDL_MUTEX_TIMEDOUT (1) if timed out, and -1 on error.

However, after debugging in GDB, what I see is the following:

  1. SDL_SemWaitTimeout calls sem_timedwait and sem_timedwait returns -1
  2. errno is set to ETIMEDOUT (110)
  3. SDL_SemWaitTimeout sets the SDL error to "Connection timed out"
  4. SDL_SemWaitTimeout returns -1
  5. My app interprets this as a failure instead of a timeout (and unfortunately my app doesn't handle this failure very gracefully :)

Looking at the documentation for sem_timedwait, it fails (-1) and sets errno=ETIMEDOUT if the timeout expires.

Assuming my analysis is correct, the attached patch should solve this problem.

On 2012-02-20 20:52:20 +0000, Sam Lantinga wrote:

Fixed, thanks!

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