gettid wrapper

[dmitris]

when trying to build on RHEL8 (with CONTAINER_ENGINE='sudo podman' LOCAL_CLANG=1 LOCAL_CLANG_FORMAT=1 make), I'm getting a build failure due to missing gettid function. This seems to be a problem with glibc... The suggested workaround gets the codebase to compile - would like you r(and CI builds' 😄 ) opinion whether this would generally work and be the right way to fix this. NB: this is cumulative with #637, I'll rebase once that one is merged.

make -C "contrib/tester-progs"
make[1]: Entering directory '/home/dmitris/gh/cilium/tetragon/contrib/tester-progs'
gcc -Wall exit-tester.c -o exit-tester -lpthread
exit-tester.c: In function ‘thread’:
exit-tester.c:34:41: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
  printf("thread: pid:%d tid:%d\n", pid, gettid());
                                         ^~~~~~
                                         getgid
/tmp/ccEikzeG.o: In function `thread':
exit-tester.c:(.text+0x168): undefined reference to `gettid'
/tmp/ccEikzeG.o: In function `main':
exit-tester.c:(.text+0x284): undefined reference to `gettid'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:24: exit-tester] Error 1
make[1]: Leaving directory '/home/dmitris/gh/cilium/tetragon/contrib/tester-progs'
make: *** [Makefile:279: tester-progs] Error 2

[tpapagian]

Thanks! Based on https://man7.org/linux/man-pages/man2/gettid.2.html it seems that gettid is introduced in glibc 2.30. So I believe that you are using an older version of glibc in you local setup.

Using syscall(__NR_gettid) seems to be the correct approach but you also need to use some type of #ifdef/#endif to check the glibc version as well to avoid errors seen in the CI.

[dmitris]

@tpapagian I added the conditional with a check of the glibc version, please take a look.

[jrfastab]

LGTM. @tpapagian wdyt? Happy with latest push?

[tpapagian]

LGTM, thanks!