Horton

Re: Cleaning up historical portability baggage

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Michael Banck <mbanck@gmx.net>
Cc: Thomas Munro <thomas.munro@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andrew Dunstan <andrew@dunslane.net>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-06-09T14:25:23Z
Lists: pgsql-hackers 
Hi,

On 2025-06-09 15:25:22 +0200, Michael Banck wrote:
> Hi Thomas,
> 
> On Thu, Aug 11, 2022 at 10:02:29PM +1200, Thomas Munro wrote:
> > Remove configure probe for sys/uio.h.
> 
> Removing the configure probe is fine, but the patch also changes
> behavior in the sense that IOV_MAX is now considered defined everywhere
> but on Windows. However, in the good-old GNU "we have no arbitrary
> limits" fashion, this breaks on GNU Hurd:
> 
> |gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wimplicit-fallthrough=3 -Wcast-function-type -Wshado
> |w=compatible-local -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -Wno-format-truncation -Wno-stringop-truncation -g -O2 -DFRONTEND -I. -I../../src/common -
> |I../../src/include  -D_GNU_SOURCE -I/usr/include/libxml2  -DVAL_CC="\"gcc\"" -DVAL_CPPFLAGS="\"-D_GNU_SOURCE -I/usr/include/libxml2\"" -DVAL_CFLAGS="\"-Wall -Wmissing-prototypes -Wpoin
> |ter-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wimplicit-fallthrough=3 -Wcast-function-type -Wshadow=compatible-local -Wformat-security 
> |-fno-strict-aliasing -fwrapv -fexcess-precision=standard -Wno-format-truncation -Wno-stringop-truncation -g -O2\"" -DVAL_CFLAGS_SL="\"-fPIC\"" -DVAL_LDFLAGS="\"-Wl,--as-needed -Wl,-rpa
> |th,'/home/demo/build-farm-19.1/buildroot/REL_16_STABLE/inst/lib',--enable-new-dtags\"" -DVAL_LDFLAGS_EX="\"\"" -DVAL_LDFLAGS_SL="\"\"" -DVAL_LIBS="\"-lpgcommon -lpgport -lxslt -lxml2 -
> |lssl -lcrypto -lgssapi_krb5 -lz -lreadline -lpthread -lm \""  -c -o file_utils.o file_utils.c
> |In file included from ../../src/include/postgres_fe.h:25,
> |                 from file_utils.c:19:
> |file_utils.c: In function 'pg_pwritev_with_retry':
> |../../src/include/port/pg_iovec.h:36:24: error: 'IOV_MAX' undeclared (first use in this function); did you mean 'INT_MAX'?
> |   36 | #define PG_IOV_MAX Min(IOV_MAX, 32)
> |      |                        ^~~~~~~
> |../../src/include/c.h:988:35: note: in definition of macro 'Min'
> |  988 | #define Min(x, y)               ((x) < (y) ? (x) : (y))
> |      |                                   ^
> |file_utils.c:474:31: note: in expansion of macro 'PG_IOV_MAX'
> |  474 |         struct iovec iov_copy[PG_IOV_MAX];
> |      |                               ^~~~~~~~~~
> |../../src/include/port/pg_iovec.h:36:24: note: each undeclared identifier is reported only once for each function it appears in
> 
> |$ grep IOV_MAX /usr/include/i386-gnu/bits/uio_lim.h     
> |#undef __IOV_MAX
> 
> Postgres built fine up and until v15 on the Hurd, so this is a build
> regression, and the fact that we define #PG_IOV_MAX to at most 32
> anyway suggest we could just #definde IOV_MAX to 16 if undefined as on
> Windows.

I think our policy basically is that if it doesn't exist on the BF, it's
unsupported. Also note that Hurd is not listed as a supported OS:
https://www.postgresql.org/docs/devel/supported-platforms.html

We can't design for OS that we don't know it's used with postgres and/or how
that OS works / what it supports.

So I reject the premise that this is a regression.

If you want to argue that we should add support for Hurd, you can do that, but
that's obviously a different discussion.

Greetings,

Andres Freund

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)