meson: compile compatibility sources separately

In the next commit we're about to introduce a precompiled header for
"git-compat-util.h". The consequence of this change is that we'll
implicitly include that header for every compilation unit that uses the
precompiled headers.

This is okay for our "normal" library sources and our builtins. But some
of our compatibility sources do not include the header on purpose, and
doing so would cause compileir errors.

Prepare for this change by splitting out compatibility sources into
their static library. Like this we can selectively enable precompiled
headers for the library sources.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

meson.build

@@ -271,6 +271,13 @@ version_gen_environment.set('GIT_VERSION', get_option('version'))
 
 compiler = meson.get_compiler('c')
 
+compat_sources = [
+  'compat/nonblock.c',
+  'compat/obstack.c',
+  'compat/open.c',
+  'compat/terminal.c',
+]
+
 libgit_sources = [
   'abspath.c',
   'add-interactive.c',
@@ -304,10 +311,6 @@ libgit_sources = [
   'commit.c',
   'common-exit.c',
   'common-init.c',
-  'compat/nonblock.c',
-  'compat/obstack.c',
-  'compat/open.c',
-  'compat/terminal.c',
   'compiler-tricks/not-constant.c',
   'config.c',
   'connect.c',
@@ -1163,7 +1166,7 @@ endif
 
 if not has_poll_h and not has_sys_poll_h
   libgit_c_args += '-DNO_POLL'
-  libgit_sources += 'compat/poll/poll.c'
+  compat_sources += 'compat/poll/poll.c'
   libgit_include_directories += 'compat/poll'
 endif
 
@@ -1179,7 +1182,7 @@ endif
 # implementation to threat things like drive prefixes specially.
 if host_machine.system() == 'windows' or not compiler.has_header('libgen.h')
   libgit_c_args += '-DNO_LIBGEN_H'
-  libgit_sources += 'compat/basename.c'
+  compat_sources += 'compat/basename.c'
 endif
 
 if compiler.has_header('paths.h')
@@ -1209,7 +1212,7 @@ if host_machine.system() != 'windows'
   foreach symbol : ['inet_ntop', 'inet_pton', 'hstrerror']
     if not compiler.has_function(symbol, dependencies: networking_dependencies)
       libgit_c_args += '-DNO_' + symbol.to_upper()
-      libgit_sources += 'compat/' + symbol + '.c'
+      compat_sources += 'compat/' + symbol + '.c'
     endif
   endforeach
 endif
@@ -1251,18 +1254,18 @@ else
 endif
 
 if host_machine.system() == 'darwin'
-  libgit_sources += 'compat/precompose_utf8.c'
+  compat_sources += 'compat/precompose_utf8.c'
   libgit_c_args += '-DPRECOMPOSE_UNICODE'
   libgit_c_args += '-DPROTECT_HFS_DEFAULT'
 endif
 
 # Configure general compatibility wrappers.
 if host_machine.system() == 'cygwin'
-  libgit_sources += [
+  compat_sources += [
     'compat/win32/path-utils.c',
   ]
 elif host_machine.system() == 'windows'
-  libgit_sources += [
+  compat_sources += [
     'compat/winansi.c',
     'compat/win32/dirent.c',
     'compat/win32/flush.c',
@@ -1289,20 +1292,20 @@ elif host_machine.system() == 'windows'
   libgit_include_directories += 'compat/win32'
   if compiler.get_id() == 'msvc'
     libgit_include_directories += 'compat/vcbuild/include'
-    libgit_sources += 'compat/msvc.c'
+    compat_sources += 'compat/msvc.c'
   else
-    libgit_sources += 'compat/mingw.c'
+    compat_sources += 'compat/mingw.c'
   endif
 endif
 
 if host_machine.system() == 'linux'
-  libgit_sources += 'compat/linux/procinfo.c'
+  compat_sources += 'compat/linux/procinfo.c'
 elif host_machine.system() == 'windows'
-  libgit_sources += 'compat/win32/trace2_win32_process_info.c'
+  compat_sources += 'compat/win32/trace2_win32_process_info.c'
 elif host_machine.system() == 'darwin'
-  libgit_sources += 'compat/darwin/procinfo.c'
+  compat_sources += 'compat/darwin/procinfo.c'
 else
-  libgit_sources += 'compat/stub/procinfo.c'
+  compat_sources += 'compat/stub/procinfo.c'
 endif
 
 if host_machine.system() == 'cygwin' or host_machine.system() == 'windows'
@@ -1315,13 +1318,13 @@ endif
 
 # Configure the simple-ipc subsystem required fro the fsmonitor.
 if host_machine.system() == 'windows'
-  libgit_sources += [
+  compat_sources += [
     'compat/simple-ipc/ipc-shared.c',
     'compat/simple-ipc/ipc-win32.c',
   ]
   libgit_c_args += '-DSUPPORTS_SIMPLE_IPC'
 else
-  libgit_sources += [
+  compat_sources += [
     'compat/simple-ipc/ipc-shared.c',
     'compat/simple-ipc/ipc-unix-socket.c',
   ]
@@ -1339,7 +1342,7 @@ if fsmonitor_backend != ''
   libgit_c_args += '-DHAVE_FSMONITOR_DAEMON_BACKEND'
   libgit_c_args += '-DHAVE_FSMONITOR_OS_SETTINGS'
 
-  libgit_sources += [
+  compat_sources += [
     'compat/fsmonitor/fsm-health-' + fsmonitor_backend + '.c',
     'compat/fsmonitor/fsm-ipc-' + fsmonitor_backend + '.c',
     'compat/fsmonitor/fsm-listen-' + fsmonitor_backend + '.c',
@@ -1355,7 +1358,7 @@ if not get_option('b_sanitize').contains('address') and get_option('regex').allo
 
   if compiler.get_define('REG_ENHANCED', prefix: '#include <regex.h>') != ''
     libgit_c_args += '-DUSE_ENHANCED_BASIC_REGULAR_EXPRESSIONS'
-    libgit_sources += 'compat/regcomp_enhanced.c'
+    compat_sources += 'compat/regcomp_enhanced.c'
   endif
 elif not get_option('regex').enabled()
   libgit_c_args += [
@@ -1364,7 +1367,7 @@ elif not get_option('regex').enabled()
     '-DNO_MBSUPPORT',
   ]
   build_options_config.set('NO_REGEX', '1')
-  libgit_sources += 'compat/regex/regex.c'
+  compat_sources += 'compat/regex/regex.c'
   libgit_include_directories += 'compat/regex'
 else
     error('Native regex support requested but not found')
@@ -1428,7 +1431,7 @@ else
 
   if get_option('b_sanitize').contains('address')
     libgit_c_args += '-DNO_MMAP'
-    libgit_sources += 'compat/mmap.c'
+    compat_sources += 'compat/mmap.c'
   else
     checkfuncs += { 'mmap': ['mmap.c'] }
   endif
@@ -1438,7 +1441,7 @@ foreach func, impls : checkfuncs
   if not compiler.has_function(func)
     libgit_c_args += '-DNO_' + func.to_upper()
     foreach impl : impls
-      libgit_sources += 'compat/' + impl
+      compat_sources += 'compat/' + impl
     endforeach
   endif
 endforeach
@@ -1449,13 +1452,13 @@ endif
 
 if not compiler.has_function('strdup')
   libgit_c_args += '-DOVERRIDE_STRDUP'
-  libgit_sources += 'compat/strdup.c'
+  compat_sources += 'compat/strdup.c'
 endif
 
 if not compiler.has_function('qsort')
   libgit_c_args += '-DINTERNAL_QSORT'
 endif
-libgit_sources += 'compat/qsort_s.c'
+compat_sources += 'compat/qsort_s.c'
 
 if compiler.has_function('getdelim')
   libgit_c_args += '-DHAVE_GETDELIM'
@@ -1511,7 +1514,7 @@ if meson.can_run_host_binaries() and compiler.run('''
   }
 ''', name: 'fread reads directories').returncode() == 0
   libgit_c_args += '-DFREAD_READS_DIRECTORIES'
-  libgit_sources += 'compat/fopen.c'
+  compat_sources += 'compat/fopen.c'
 endif
 
 if not meson.is_cross_build() and fs.exists('/dev/tty')
@@ -1745,14 +1748,22 @@ else
 endif
 
 libgit = declare_dependency(
-  link_with: static_library('git',
-    sources: libgit_sources,
-    c_args: libgit_c_args + [
-      '-DGIT_VERSION_H="' + version_def_h.full_path() + '"',
-    ],
-    dependencies: libgit_dependencies,
-    include_directories: libgit_include_directories,
-  ),
+  link_with: [
+    static_library('compat',
+      sources: compat_sources,
+      c_args: libgit_c_args,
+      dependencies: libgit_dependencies,
+      include_directories: libgit_include_directories,
+    ),
+    static_library('git',
+      sources: libgit_sources,
+      c_args: libgit_c_args + [
+        '-DGIT_VERSION_H="' + version_def_h.full_path() + '"',
+      ],
+      dependencies: libgit_dependencies,
+      include_directories: libgit_include_directories,
+    ),
+  ],
   compile_args: libgit_c_args,
   dependencies: libgit_dependencies,
   include_directories: libgit_include_directories,