Subject: Building with meson on NixOS/nixpkgs

From: Wolfgang Walther <[email-masked]>
Date: Sat, 16 Mar 2024 12:48:31 +0100

To build on NixOS/nixpkgs I came up with a few small patches to 
meson.build. All of this works fine with Autoconf/Make already.

From 24ae72b9b0adc578c6729eff59c9038e6b4ac517 Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <[email-masked]>
Date: Sat, 2 Mar 2024 17:18:38 +0100
Subject: [PATCH 1/3] Fallback to uuid for ossp-uuid with meson

The upstream name for the ossp-uuid package / pkg-config file is "uuid". Many
distributions change this to be "ossp-uuid" to not conflict with e2fsprogs.

This lookup fails on distributions which don't change this name, for example
NixOS / nixpkgs. Both "ossp-uuid" and "uuid" are also checked in configure.ac.
---
 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index c8fdfeb0ec3..d9ad1ce902f 100644
--- a/meson.build
+++ b/meson.build
@@ -1346,7 +1346,7 @@ if uuidopt != 'none'
     uuidfunc = 'uuid_to_string'
     uuidheader = 'uuid.h'
   elif uuidopt == 'ossp'
-    uuid = dependency('ossp-uuid', required: true)
+    uuid = dependency('ossp-uuid', 'uuid', required: true)
     uuidfunc = 'uuid_export'
     uuidheader = 'uuid.h'
   else
-- 
2.44.0

From 56e0abbcc3b950b6e93eddc6ede453ce529423ea Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <[email-masked]>
Date: Sat, 2 Mar 2024 22:06:25 +0100
Subject: [PATCH 2/3] Fallback to clang in PATH with meson

Some distributions put clang into a different path than the llvm binary path.

For example, this is the case on NixOS / nixpkgs, which failed to find clang
with meson before this patch.
---
 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index d9ad1ce902f..7c64fb04ea5 100644
--- a/meson.build
+++ b/meson.build
@@ -759,7 +759,7 @@ if add_languages('cpp', required: llvmopt, native: false)
     llvm_binpath = llvm.get_variable(configtool: 'bindir')
 
     ccache = find_program('ccache', native: true, required: false)
-    clang = find_program(llvm_binpath / 'clang', required: true)
+    clang = find_program(llvm_binpath / 'clang', 'clang', required: true)
   endif
 elif llvmopt.auto()
   message('llvm requires a C++ compiler')
-- 
2.44.0

From 62f10689d843227fca6d54e86462d0be5c4f434f Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <[email-masked]>
Date: Mon, 11 Mar 2024 19:54:41 +0100
Subject: [PATCH 3/3] Support absolute bindir/libdir in regression tests with
 meson

Passing an absolute bindir/libdir will install the binaries and libraries to
<build>/tmp_install/<bindir> and <build>/tmp_install/<libdir> respectively.

This is path is correctly passed to the regression test suite via configure/make,
but not via meson, yet. This is because the "/" operator in the following expression
throws away the whole left side when the right side is an absolute path:

  test_install_location / get_option('libdir')

This was already correctly handled for dir_prefix, which is likely absolute as well.
This patch handles both bindir and libdir in the same way - prefixing absolute paths
with the tmp_install path correctly.
---
 meson.build | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/meson.build b/meson.build
index 7c64fb04ea5..e8438209058 100644
--- a/meson.build
+++ b/meson.build
@@ -3044,15 +3044,17 @@ test_install_destdir = meson.build_root() / 'tmp_install/'
 if build_system != 'windows'
   # On unixoid systems this is trivial, we just prepend the destdir
   assert(dir_prefix.startswith('/')) # enforced by meson
-  test_install_location = '@0@@1@'.format(test_install_destdir, dir_prefix)
+  temp_install_bindir = '@0@@1@'.format(test_install_destdir, dir_prefix / dir_bin)
+  temp_install_libdir = '@0@@1@'.format(test_install_destdir, dir_prefix / dir_lib)
 else
   # drives, drive-relative paths, etc make this complicated on windows, call
   # into a copy of meson's logic for it
   command = [
     python, '-c',
     'import sys; from pathlib import PurePath; d1=sys.argv[1]; d2=sys.argv[2]; print(str(PurePath(d1, *PurePath(d2).parts[1:])))',
-    test_install_destdir, dir_prefix]
-  test_install_location = run_command(command, check: true).stdout().strip()
+    test_install_destdir]
+  temp_install_bindir = run_command(command, dir_prefix / dir_bin, check: true).stdout().strip()
+  temp_install_libdir = run_command(command, dir_prefix / dir_lib, check: true).stdout().strip()
 endif
 
 meson_install_args = meson_args + ['install'] + {
@@ -3089,7 +3091,6 @@ testport = 40000
 
 test_env = environment()
 
-temp_install_bindir = test_install_location / get_option('bindir')
 test_initdb_template = meson.build_root() / 'tmp_install' / 'initdb-template'
 test_env.set('PG_REGRESS', pg_regress.full_path())
 test_env.set('REGRESS_SHLIB', regress_module.full_path())
@@ -3104,7 +3105,7 @@ test_env.set('PG_TEST_EXTRA', get_option('PG_TEST_EXTRA'))
 # that works (everything but windows, basically). On windows everything
 # library-like gets installed into bindir, solving that issue.
 if library_path_var != ''
-  test_env.prepend(library_path_var, test_install_location / get_option('libdir'))
+  test_env.prepend(library_path_var, temp_install_libdir)
 endif

-- 
2.44.0