Set RPATH for all non-system libs with absolute paths

If a pkg-config dependency has multiple libraries in it, which is the
most common case when it has a Requires: directive, or when it has
multiple -l args in Libs: (rare), then we don't add -Wl,-rpath
directives to it when linking.

The existing test wasn't catching it because it was linking to
a pkgconfig file with a single library in it. Update the test to
demonstrate this.

This function was originally added for shared libraries in the source
directory, which explains the name:
https://github.com/mesonbuild/meson/pull/2397

However, since now it is also used for linking to *all* non-system
shared libraries that we link to with absolute paths:
https://github.com/mesonbuild/meson/pull/3092

But that PR is incomplete / wrong, because only adding RPATHs for
dependencies that specify a single library, which is simply
inconsistent. Things will work for some dependencies and not work for
others, with no logical reason for it.

We should add RPATHs for *all* libraries. There are no special length
limits for RPATHs that I can find.

For ELF, DT_RPATH or DT_RUNPATH are used, which are just stored in
a string table (DT_STRTAB). The maximum length is only a problem when
editing pre-existing tags.

For Mach-O, each RPATH is stored in a separate LC_RPATH entry so there
are no length issues there either.

Fixes https://github.com/mesonbuild/meson/issues/9543

Fixes https://github.com/mesonbuild/meson/issues/4372

mesonbuild/backend/backends.py

@@ -751,37 +751,36 @@ class Backend:
         return dirs
 
     @lru_cache(maxsize=None)
-    def rpaths_for_bundled_shared_libraries(self, target: build.BuildTarget, exclude_system: bool = True) -> 'ImmutableListProtocol[str]':
-        paths: T.List[str] = []
+    def rpaths_for_non_system_absolute_shared_libraries(self, target: build.BuildTarget, exclude_system: bool = True) -> 'ImmutableListProtocol[str]':
+        paths: OrderedSet[str] = OrderedSet()
         for dep in target.external_deps:
             if not isinstance(dep, (dependencies.ExternalLibrary, dependencies.PkgConfigDependency)):
                 continue
-            la = dep.link_args
-            if len(la) != 1 or not os.path.isabs(la[0]):
-                continue
-            # The only link argument is an absolute path to a library file.
-            libpath = la[0]
-            libdir = os.path.dirname(libpath)
-            if exclude_system and self._libdir_is_system(libdir, target.compilers, self.environment):
-                # No point in adding system paths.
-                continue
-            # Don't remove rpaths specified in LDFLAGS.
-            if libdir in self.get_external_rpath_dirs(target):
-                continue
-            # Windows doesn't support rpaths, but we use this function to
-            # emulate rpaths by setting PATH, so also accept DLLs here
-            if os.path.splitext(libpath)[1] not in ['.dll', '.lib', '.so', '.dylib']:
-                continue
-            if libdir.startswith(self.environment.get_source_dir()):
-                rel_to_src = libdir[len(self.environment.get_source_dir()) + 1:]
-                assert not os.path.isabs(rel_to_src), f'rel_to_src: {rel_to_src} is absolute'
-                paths.append(os.path.join(self.build_to_src, rel_to_src))
-            else:
-                paths.append(libdir)
+            for libpath in dep.link_args:
+                # For all link args that are absolute paths to a library file, add RPATH args
+                if not os.path.isabs(libpath):
+                    continue
+                libdir = os.path.dirname(libpath)
+                if exclude_system and self._libdir_is_system(libdir, target.compilers, self.environment):
+                    # No point in adding system paths.
+                    continue
+                # Don't remove rpaths specified in LDFLAGS.
+                if libdir in self.get_external_rpath_dirs(target):
+                    continue
+                # Windows doesn't support rpaths, but we use this function to
+                # emulate rpaths by setting PATH, so also accept DLLs here
+                if os.path.splitext(libpath)[1] not in ['.dll', '.lib', '.so', '.dylib']:
+                    continue
+                if libdir.startswith(self.environment.get_source_dir()):
+                    rel_to_src = libdir[len(self.environment.get_source_dir()) + 1:]
+                    assert not os.path.isabs(rel_to_src), f'rel_to_src: {rel_to_src} is absolute'
+                    paths.add(os.path.join(self.build_to_src, rel_to_src))
+                else:
+                    paths.add(libdir)
         for i in chain(target.link_targets, target.link_whole_targets):
             if isinstance(i, build.BuildTarget):
-                paths.extend(self.rpaths_for_bundled_shared_libraries(i, exclude_system))
-        return paths
+                paths.update(self.rpaths_for_non_system_absolute_shared_libraries(i, exclude_system))
+        return list(paths)
 
     # This may take other types
     def determine_rpath_dirs(self, target: T.Union[build.BuildTarget, build.CustomTarget, build.CustomTargetIndex]
@@ -794,7 +793,7 @@ class Backend:
             result = OrderedSet()
             result.add('meson-out')
         if isinstance(target, build.BuildTarget):
-            result.update(self.rpaths_for_bundled_shared_libraries(target))
+            result.update(self.rpaths_for_non_system_absolute_shared_libraries(target))
             target.rpath_dirs_to_remove.update([d.encode('utf-8') for d in result])
         return tuple(result)
 
@@ -1072,7 +1071,7 @@ class Backend:
         if isinstance(target, build.BuildTarget):
             prospectives.update(target.get_transitive_link_deps())
             # External deps
-            for deppath in self.rpaths_for_bundled_shared_libraries(target, exclude_system=False):
+            for deppath in self.rpaths_for_non_system_absolute_shared_libraries(target, exclude_system=False):
                 result.add(os.path.normpath(os.path.join(self.environment.get_build_dir(), deppath)))
         for bdep in extra_bdeps:
             prospectives.add(bdep)

test cases/common/44 pkgconfig-gen/answer.c

@@ -0,0 +1,3 @@
+int answer_to_life_the_universe_and_everything(void) {
+    return 42;
+}

test cases/common/44 pkgconfig-gen/foo.c

@@ -0,0 +1,7 @@
+#include"simple.h"
+
+int answer_to_life_the_universe_and_everything (void);
+
+int simple_function(void) {
+    return answer_to_life_the_universe_and_everything();
+}

test cases/common/44 pkgconfig-gen/meson.build

@@ -42,13 +42,21 @@ test('pkgconfig-validation', pkgconfig,
   args: ['--validate', 'simple'],
   env: [ 'PKG_CONFIG_PATH=' + meson.current_build_dir() + '/meson-private' ])
 
+answerlib = shared_library('answer', 'answer.c')
+
+pkgg.generate(answerlib,
+  name : 'libanswer',
+  description : 'An answer library.',
+)
+
 # Test that name_prefix='' and name='libfoo' results in '-lfoo'
-lib2 = shared_library('libfoo', 'simple.c',
+lib2 = shared_library('libfoo', 'foo.c',
+  link_with: answerlib,
   name_prefix : '',
   version : libver)
 
-pkgg.generate(
-  libraries : lib2,
+pkgg.generate(lib2,
+  libraries : [lib2, answerlib],
   name : 'libfoo',
   version : libver,
   description : 'A foo library.',

test cases/common/44 pkgconfig-gen/test.json

@@ -3,6 +3,7 @@
     {"type": "file", "file": "usr/include/simple.h"},
     {"type": "file", "file": "usr/lib/libstat2.a"},
     {"type": "file", "file": "usr/lib/pkgconfig/simple.pc"},
+    {"type": "file", "file": "usr/lib/pkgconfig/libanswer.pc"},
     {"type": "file", "file": "usr/lib/pkgconfig/libfoo.pc"},
     {"type": "file", "file": "usr/lib/pkgconfig/libhello.pc"},
     {"type": "file", "file": "usr/lib/pkgconfig/libhello_nolib.pc"},

unittests/allplatformstests.py

@@ -1595,7 +1595,7 @@ class AllPlatformTests(BasePlatformTests):
         foo_dep = PkgConfigDependency('libfoo', env, kwargs)
         # Ensure link_args are properly quoted
         libdir = PurePath(prefix) / PurePath(libdir)
-        link_args = ['-L' + libdir.as_posix(), '-lfoo']
+        link_args = ['-L' + libdir.as_posix(), '-lfoo', '-lanswer']
         self.assertEqual(foo_dep.get_link_args(), link_args)
         # Ensure include args are properly quoted
         incdir = PurePath(prefix) / PurePath('include')