[Bug 874418] Re: linking against librt doesn't provide sem_post

[Gary Duzan]

If this is going to be the case going forward, then the sem_* man pages
should be updated to indicate that -lrt is no longer sufficient to use
semaphores. I don't have a problem with the change since LSB says to use
libpthread, anyway, but if the behavior is going to change then the
documentation that suggests use of the old behavior should be changed.

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https://bugs.launchpad.net/bugs/874418

Title:
  linking against librt doesn't provide sem_post

Status in “eglibc” package in Ubuntu:
  Invalid

Bug description:
  We have software that uses semaphores but not pthreads. Therefore, our
  code links against librt, as documented in the sem_post man page. This
  worked fine in 10.04 and 11.04, but not in 11.10.

  > cat a.c
  #include <semaphore.h>
  int main()
  {
      sem_t *mysem;

      int ret;

      ret = sem_post(mysem);
      return 0;
  }
  > gcc -g -lrt -o a a.c
  /tmp/ccUadHKv.o: In function `main':
  a.c:8: undefined reference to `sem_post'
  collect2: ld returned 1 exit status

  ProblemType: Bug
  DistroRelease: Ubuntu 11.10
  Package: libc6-dev 2.13-20ubuntu5
  ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
  Uname: Linux 3.0.0-12-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 1.23-0ubuntu3
  Architecture: amd64
  Date: Fri Oct 14 12:30:58 2011
  SourcePackage: eglibc
  UpgradeStatus: Upgraded to oneiric on 2011-10-07 (6 days ago)

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