Horton

Re: [RFC] building postgres with meson - autogenerated headers

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: pgsql-hackers@postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2022-02-07T19:24:47Z
Lists: pgsql-hackers 
Hi,

I've been wondering whether we should try to have the generated pg_config.h
look as similar as possible to autoconf/autoheader's, or not. And whether the
way autoconf/autoheader define symbols makes sense when not using either
anymore.

To be honest, I do not really understand the logic behind when autoconf ends
up with #defines that define a macro to 0/1 and when a macro ends defined/or
not and when we end up with a macro defined to 1 or not defined at all.

So far I've tried to mirror the logic, but not the description / comment
formatting of the individual macros.

The "defined to 1 or not defined at all" behaviour is a mildly awkward to
achieve with meson, because it doesn't match the behaviour for booleans
options meson has (there are two builtin behaviours, one to define/undefine a
macro, the other to set the macro to 0/1. But there's none that defines a
macro to 1 or undefines it).

Probably best to initially have the macros defined as similar as reasonably
possible, but subsequently clean things up a bit.


A second aspect that I'm wondering about is whether we should try to split
pg_config.h output a bit:

With meson it's easy to change options like whether to build with some
dependency in an existing build tree and then still get a reliable build
result (ninja rebuilds if the commandline changed from the last invocation).

But right now doing so often ends up with way bigger rebuilds than necessary,
because for a lot of options we add #define USE_LDAP 1 etc to pg_config.h,
which of course requires rebuilding a lot of files. Even though most of these
symbols are only checked in a handful of files, often only .c files.

It seems like it might make sense to separate out defines that depend on the
compiler / "standard libraries" (e.g. {SIZEOF,ALIGNOF}_*,
HAVE_DECL_{STRNLEN,...}, HAVE_*_H) from feature defines (like
USE_{LDAP,ICU,...}). The header containing the latter could then included in
the places needing it (or we could have one header for each of the places
using it).

Perhaps we should also separate out configure-time settings like BLCKSZ,
DEF_PGPORT, etc. Realistically most of them are going to require a "full tree"
recompile anway, but it seems like it might make things easier to understand.

I think a split into pg_config_{platform,features,settings}.h could make sense.

Similar to above, it's probably best to do this separately after merging meson
support. But knowing what the split should eventually look like would be
helpful before, to ensure it's easy to do.

Greetings,

Andres Freund

Commits

  1. meson: Add 'running' test setup, as a replacement for installcheck

  2. meson: Add support for building with precompiled headers

  3. windows: Adjust FD_SETSIZE via commandline define

  4. meson: docs: Add xml{lint,proc} wrapper to collect dependencies

  5. meson: ecpg: Split definition of static and shared libraries

  6. windows: Set UMDF_USING_NTSTATUS globally, include ntstatus.h

  7. ci: Add hint about downloadable logs to README

  8. meson: Set up absolute rpaths to libdir

  9. meson: Include CFLAGS/c_args in summary and pg_config output

  10. windows: remove date from version number in win32ver.rc

  11. meson: Add initial version of meson based build system

  12. ci: windows: set error mode to not include SEM_NOGPFAULTERRORBOX

  13. Refactor PG_TEST_EXTRA logic in autoconf build

  14. Split TESTDIR into TESTLOGDIR and TESTDATADIR

  15. Don't hardcode tmp_check/ as test directory for tap tests

  16. Extend gendef.pl in preparation for meson

  17. Include c.h instead of postgres.h in src/port/*p{read,write}*.c

  18. Remove DLLTOOL, DLLWRAP from configure / Makefile.global.in

  19. Run xmllint validation only once

  20. Bump minimum Perl version to 5.14

  21. Move gramparse.h to src/backend/parser

  22. Run perltidy over Catalog.pm

  23. Parse catalog .dat files as a whole when compiling the backend

  24. Build all Flex files standalone

  25. Move private declarations shared between guc.c and guc-file.l to new header

  26. Preparatory refactoring for compiling guc-file.c standalone

  27. Move darwin sysroot determination into separate file

  28. Fix MSVC warning in compat_informix/rnull.pgc

  29. solaris: Use versioning scripts instead of -Bsymbolic

  30. Change shared library installation naming on macOS

  31. regress: allow to specify directory containing expected files, for ecpg

  32. Don't add HAVE_LDAP_H HAVE_WINLDAP_H to pg_config.h

  33. Refactor dtrace postprocessing make rules

  34. Add output directory option to gen_node_support.pl

  35. Add output directory argument to generate-unicode_norm_table.pl

  36. Add output file argument to generate-errcodes.pl

  37. Add output path arg in generate-lwlocknames.pl

  38. Move snowball_create.sql creation into perl file

  39. ecpg: Output dir, source dir, stamp file argument for preproc/*.pl

  40. psql: Output dir and dependency generation for sql_help

  41. Deal with paths containing \ and spaces in basebackup_to_shell tests

  42. Remove LLVM_CONFIG from Makefile.global.in

  43. Make update-unicode target work in vpath builds

  44. Refactor DLSUFFIX handling

  45. ldap tests: Add paths for openbsd.

  46. ldap tests: Don't run on unsupported operating systems.

  47. Remove check for accept() argument types

  48. Move our p{read,write}v replacements into their own files.

  49. Adjust yywrap macro for non-reentrant scanners for MSVC.

  50. Remove any -arch switches given in ExtUtils::Embed's ldopts from our

  51. Change PL/Perl and Pg interface build to use configured compiler and

  52. Apparently, on some systems, ExtUtils::Embed and MakeMaker are slightly