Horton

Cleaning up historical portability baggage

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-07-10T01:45:23Z
Lists: pgsql-hackers

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Hello,

I wonder how much dead code for ancient operating systems we could now
drop.  Here are some easier cases, I think, and one tricky one that
might take some debate.  I think it makes a lot of sense to say that
we expect at least POSIX-1:2001, because that corresponds to C99, with
the thread option because every targeted system has that.

0001-Remove-dead-pg_pread-and-pg_pwrite-replacement-code.patch
0002-Remove-dead-getrusage-replacement-code.patch
0003-Remove-dead-setenv-unsetenv-replacement-code.patch
0004-Remove-dead-handling-for-pre-POSIX-sigwait.patch
0005-Remove-dead-getpwuid_r-replacement-code.patch
0006-Remove-disable-thread-safety.patch

Clearly there is more stuff like this (eg more _r functions, they're
just a touch more complicated), but this is a start.  I mention these
now in case it's helpful for the Meson work, and just generally
because I wanted to clean up after the retirement of ancient HP-UX.
The threads patch probably needs more polish and is extracted from
another series I'll propose in a later CF to do some more constructive
work on threads where it'd be helpful not to have to deal with 'no
threads' builds, but I figured it could also pitch this part along
with the other basic POSIX modernisation stuff.

I pulled the configure output from the oldest releases of each
supported target OS, namely:

  * hornet, AIX 7.1
  * wrasse, Solaris 11.3
  * pollock, illumos rolling
  * loach, FreeBSD 12.2
  * conchuela, DragonflyBSD 6.0
  * morepork, OpenBSD 6.9
  * sidewinder, NetBSD 9.2
  * prairiedog, macOS 10.4 (vintage system most likely to cause problems)
  * clam, Linux 3.10/RHEL 7
  * fairiewren, Windows/Mingw with configure

I checked for HAVE_PREAD HAVE_PWRITE HAVE_GETRUSAGE HAVE_SETENV
HAVE_UNSETENV HAVE_GETPWUID_R, and the only missing ones were:

HAVE_PREAD is missing on windows
HAVE_PWRITE is missing on windows
HAVE_GETRUSAGE is missing on windows
HAVE_GETPWUID_R is missing on windows

We either have completely separate code paths or replacement functions
for these.

The pwritev/preadv functions are unfortunately not standardised by
POSIX (I dunno why, it's the obvious combination of the p* and *v
functions) despite every OS in the list having them except for Solaris
and old macOS.  Oh well.

Commits

  1. Make sure IOV_MAX is defined.

  2. Doc: Abstract AF_UNIX sockets don't work on Windows.

  3. Clean up inconsistent use of fflush().

  4. Remove configure probe for sockaddr_in6 and require AF_INET6.

  5. Remove configure probes for sockaddr_storage members.

  6. Remove configure probe for netinet/tcp.h.

  7. Fix macro problem with gai_strerror on Windows.

  8. Remove configure probe for net/if.h.

  9. mstcpip.h is not missing on MinGW.

  10. Remove dead ifaddr.c fallback code.

  11. Remove configure probe for gethostbyname_r.

  12. Remove replacement code for getaddrinfo.

  13. Remove configure probe for struct sockaddr_storage.

  14. Remove HAVE_UNIX_SOCKETS.

  15. Remove configurability of PPC spinlock assembly code.

  16. Remove configure probe for shl_load library.

  17. Remove configure probe for sys/select.h.

  18. Remove configure probes for sys/un.h and struct sockaddr_un.

  19. Remove configure probes for sys/ipc.h, sys/sem.h, sys/shm.h.

  20. Remove configure probe for sys/resource.h and refactor.

  21. Remove configure probe for sys/uio.h.

  22. Fix obsolete comments in instr_time.h.

  23. aix: fix misreading of condition in 8f12a4e7add

  24. aix: Remove checks for very old OS versions

  25. windows: Remove HAVE_MINIDUMP_TYPE test

  26. solaris: Remove unnecessary gcc / gnu ld vs sun studio differences

  27. Trust a few system headers to stand on their own

  28. Rely on __func__ being supported

  29. Simplify replacement code for strtof.

  30. Simplify gettimeofday for Windows.

  31. Simplify gettimeofday() fallback logic.

  32. Remove fallbacks for strtoll, strtoull.

  33. Remove configure probe for fdatasync.

  34. Remove configure probe for clock_gettime.

  35. Simplify replacement code for preadv and pwritev.

  36. Remove dead pread and pwrite replacement code.

  37. Remove dead setenv, unsetenv replacement code.

  38. Remove configure probes for poll and poll.h.

  39. Remove configure probe for link.

  40. Remove configure probes for symlink/readlink, and dead code.

  41. Remove configure probe for setsid.

  42. Remove configure probe for shm_open.

  43. Remove configure probe and related tests for getrlimit.

  44. Remove configure probe for dlopen, and refactor.

  45. Remove dead getpwuid_r replacement code.

  46. Remove dead handling for pre-POSIX sigwait().

  47. Remove dead getrusage replacement code.

  48. Cygwin and Mingw floating-point fixes.

  49. Support platforms where strtoll/strtoull are spelled __strtoll/__strtoull.

  50. Arrange to supply declarations for strtoll/strtoull if needed.

  51. Lock down regression testing temporary clusters on Windows.

  52. Secure Unix-domain sockets of "make check" temporary clusters.

  53. Add configure checks for strtoll, strtoull (or strto[u]q). Disable

  54. Portability fix for old SunOS releases: fflush(NULL)