meson: add test-libsystemd-sym, fix linking of libsystemd

This is quite messy. I think libtool might have been using something
like -Wl,--whole-archive, but I don't think meson has support for that.
For now, just recompile all the sources for linking into libsystemd
directly. This should not matter much for efficiency, since it's a
few small files.

src/systemd/meson.build

@@ -1,6 +1,6 @@
 # -*- mode: meson -*-
 
-headers = '''
+systemd_headers = files('''
   sd-bus.h
   sd-bus-protocol.h
   sd-bus-vtable.h
@@ -10,8 +10,7 @@ headers = '''
   sd-journal.h
   sd-login.h
   sd-messages.h
-  _sd-common.h
-'''.split()
+'''.split())
 
 #  sd-device.h
 #  sd-hwdb.h
@@ -30,4 +29,7 @@ headers = '''
 #  sd-resolve.h
 #  sd-utf8.h
 
-install_headers(headers, subdir : 'systemd')
+install_headers(
+  systemd_headers,
+  '_sd-common.h',
+  subdir : 'systemd')

src/test/generate-sym-test.py

@@ -0,0 +1,23 @@
+#!/usr/bin/python3
+import sys, re
+
+print('#include <stdio.h>')
+for header in sys.argv[2:]:
+    print('#include "{}"'.format(header.split('/')[-1]))
+
+print('''
+void* functions[] = {''')
+
+for line in open(sys.argv[1]):
+    match = re.search('^ +([a-zA-Z0-9_]+);', line)
+    if match:
+        print('    {},'.format(match.group(1)))
+
+print('''};
+
+int main(void) {
+    unsigned i;
+    for (i = 0; i < sizeof(functions)/sizeof(void*); i++)
+         printf("%p\\n", functions[i]);
+    return 0;
+}''')

src/test/meson.build

@@ -17,6 +17,19 @@ test_env.set('SYSTEMD_LANGUAGE_FALLBACK_MAP', language_fallback_map)
 test_env.set('PATH', path)
 test_env.prepend('PATH', meson.build_root())
 
+############################################################
+
+generate_sym_test_py = find_program('generate-sym-test.py')
+
+test_libsystemd_sym_c = custom_target(
+  'test-libsystemd-sym.c',
+  input : [libsystemd_sym_path] + systemd_headers,
+  output : 'test-libsystemd-sym.c',
+  command : [generate_sym_test_py, libsystemd_sym_path] + systemd_headers,
+  capture : true)
+
+############################################################
+
 tests += [
   [['src/test/test-device-nodes.c'],
    [libshared],