Re: BUG #19095: Test if function exit() is used fail when linked static

Hello Hackers,

While reproducing a static linking issue between libpq and libcrypto.a,
I observed that the Makefile's symbol check incorrectly reports missing
exit() symbols because 'grep exit' also matches 'atexit' and
'OPENSSL_atexit', etc.

As discussed in the thread by Michael Paquier
(https://www.postgresql.org/message-id/aQA1obboZFjqjaBI%40paquier.xyz),
it seems a related fix was committed earlier. However, I was able to
reproduce this issue again using PostgreSQL 18 (latest release).

Steps to reproduce:
  nm -A -u ./src/interfaces/libpq/libpq.a /usr/lib/x86_64-linux-gnu/libcrypto.a 2>/dev/null | grep -v __cxa_atexit | grep exit

Output:
  /usr/lib/x86_64-linux-gnu/libcrypto.a:libcrypto-lib-init.o:                 U atexit
  /usr/lib/x86_64-linux-gnu/libcrypto.a:libdefault-lib-rand_unix.o:           U OPENSSL_atexit

This falsely triggers an undefined exit() error.  
[1]Changing the grep pattern to match the exact symbol ('grep -x exit') prevents
such false positives.

[2]Alternatively, excluding pthread_exit() (similar to
__cxa_atexit) would also avoid the issue.

Expected (after fix):
  no output — no false positives.

Patch attached.I would love to hear any suggestions from the committers.

Best regards,  
Vasuki M  

CDAC Chennai.