depfixer: change fix_darwin to act like fix_rpathtype_entry

This somewhat aligns "darwin" (Mach-O) with how ELF RPATHs are treated.
Instead of blindly removing all RPATHs, only remove the ones that are in
the rpath_dirs_to_remove set.  This way, RPATHs that were added by the
toolchain or user are left untouched.

It is important not to remove RPATHs as they may be vital for the
executable at runtime.  Issues #12045 and #12288 are examples of this.

Issue: #12045
Signed-off-by: Fabian Groffen <grobian@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>

mesonbuild/scripts/depfixer.py

@@ -379,7 +379,7 @@ def fix_elf(fname: str, rpath_dirs_to_remove: T.Set[bytes], new_rpath: T.Optiona
             # note: e.get_rpath() and e.get_runpath() may be useful
             e.fix_rpath(fname, rpath_dirs_to_remove, new_rpath)
 
-def get_darwin_rpaths_to_remove(fname: str) -> T.List[str]:
+def get_darwin_rpaths(fname: str) -> T.List[str]:
     p, out, _ = Popen_safe(['otool', '-l', fname], stderr=subprocess.DEVNULL)
     if p.returncode != 0:
         raise subprocess.CalledProcessError(p.returncode, p.args, out)
@@ -397,43 +397,32 @@ def get_darwin_rpaths_to_remove(fname: str) -> T.List[str]:
             result.append(rp)
     return result
 
-def fix_darwin(fname: str, new_rpath: str, final_path: str, install_name_mappings: T.Dict[str, str]) -> None:
+def fix_darwin(fname: str, rpath_dirs_to_remove: T.Set[bytes], new_rpath: str, final_path: str, install_name_mappings: T.Dict[str, str]) -> None:
     try:
-        rpaths = get_darwin_rpaths_to_remove(fname)
+        old_rpaths = get_darwin_rpaths(fname)
     except subprocess.CalledProcessError:
         # Otool failed, which happens when invoked on a
         # non-executable target. Just return.
         return
+    new_rpaths: OrderedSet[str] = OrderedSet()
+    if new_rpath:
+        new_rpaths.update(new_rpath)
+    # filter out build-only rpath entries, like in
+    # fix_rpathtype_entry
+    remove_rpaths = [x.decode('utf8') for x in rpath_dirs_to_remove]
+    for rpath_dir in old_rpaths:
+        if rpath_dir and rpath_dir not in remove_rpaths:
+            new_rpaths.add(rpath_dir)
     try:
         args = []
-        if rpaths:
-            # TODO: fix this properly, not totally clear how
-            #
-            # removing rpaths from binaries on macOS has tons of
-            # weird edge cases. For instance, if the user provided
-            # a '-Wl,-rpath' argument in LDFLAGS that happens to
-            # coincide with an rpath generated from a dependency,
-            # this would cause installation failures, as meson would
-            # generate install_name_tool calls with two identical
-            # '-delete_rpath' arguments, which install_name_tool
-            # fails on. Because meson itself ensures that it never
-            # adds duplicate rpaths, duplicate rpaths necessarily
-            # come from user variables. The idea of using OrderedSet
-            # is to remove *at most one* duplicate RPATH entry. This
-            # is not optimal, as it only respects the user's choice
-            # partially: if they provided a non-duplicate '-Wl,-rpath'
-            # argument, it gets removed, if they provided a duplicate
-            # one, it remains in the final binary. A potentially optimal
-            # solution would split all user '-Wl,-rpath' arguments from
-            # LDFLAGS, and later add them back with '-add_rpath'.
-            for rp in OrderedSet(rpaths):
-                args += ['-delete_rpath', rp]
-            subprocess.check_call(['install_name_tool', fname] + args,
-                                  stdout=subprocess.DEVNULL,
-                                  stderr=subprocess.DEVNULL)
-        args = []
-        if new_rpath:
-            args += ['-add_rpath', new_rpath]
+        # compute diff, translate it into -delete_rpath and -add_rpath
+        # calls
+        for path in new_rpaths:
+            if path not in old_rpaths:
+                args += ['-add_rpath', path]
+        for path in old_rpaths:
+            if path not in new_rpaths:
+                args += ['-delete_rpath', path]
         # Rewrite -install_name @rpath/libfoo.dylib to /path/to/libfoo.dylib
         if fname.endswith('dylib'):
             args += ['-id', final_path]
@@ -492,4 +481,4 @@ def fix_rpath(fname: str, rpath_dirs_to_remove: T.Set[bytes], new_rpath: T.Union
     if INSTALL_NAME_TOOL:
         if isinstance(new_rpath, bytes):
             new_rpath = new_rpath.decode('utf8')
-        fix_darwin(fname, new_rpath, final_path, install_name_mappings)
+        fix_darwin(fname, rpath_dirs_to_remove, new_rpath, final_path, install_name_mappings)