Fix shared library symlink aliasing on install

Set the rules for the symlinking on the target itself, and then reuse
that information while generating aliases during the build, and then
pass it to the install script too.

mesonbuild/backend/ninjabackend.py

@@ -626,7 +626,7 @@ int dummy;
                              self.environment.get_import_lib_dir(),
                              # It has no aliases, should not be stripped, and
                              # doesn't have an install_rpath
-                             [], False, '']
+                             {}, False, '']
                         d.targets.append(i)
                     outdir = self.environment.get_shared_lib_dir()
                 elif isinstance(t, build.StaticLibrary):
@@ -641,16 +641,16 @@ int dummy;
                         # Install the debug symbols file in the same place as
                         # the target itself. It has no aliases, should not be
                         # stripped, and doesn't have an install_rpath
-                        i = [self.get_target_debug_filename(t), outdir, [], False, '']
+                        i = [self.get_target_debug_filename(t), outdir, {}, False, '']
                         d.targets.append(i)
                 if isinstance(t, build.BuildTarget):
-                    i = [self.get_target_filename(t), outdir, t.get_aliaslist(),\
+                    i = [self.get_target_filename(t), outdir, t.get_aliases(),
                          should_strip, t.install_rpath]
                     d.targets.append(i)
                 elif isinstance(t, build.CustomTarget):
                     for output in t.get_outputs():
                         f = os.path.join(self.get_target_dir(t), output)
-                        d.targets.append([f, outdir, [], False, None])
+                        d.targets.append([f, outdir, {}, False, None])
 
     def generate_custom_install_script(self, d):
         d.install_scripts = self.build.install_scripts
@@ -2087,22 +2087,15 @@ rule FORTRAN_DEP_HACK
 
     def generate_shlib_aliases(self, target, outdir):
         basename = target.get_filename()
-        aliases = target.get_aliaslist()
+        aliases = target.get_aliases()
-        for i, alias in enumerate(aliases):
+        for alias, to in aliases.items():
             aliasfile = os.path.join(self.environment.get_build_dir(), outdir, alias)
             try:
                 os.remove(aliasfile)
             except Exception:
                 pass
-            # If both soversion and version are set and to different values,
-            # the .so symlink must point to the soversion symlink rather than the
-            # original file.
-            if i == 0 and len(aliases) > 1:
-                pointed_to_filename = aliases[1]
-            else:
-                pointed_to_filename = basename
             try:
-                os.symlink(pointed_to_filename, aliasfile)
+                os.symlink(to, aliasfile)
             except NotImplementedError:
                 mlog.debug("Library versioning disabled because symlinks are not supported.")
             except OSError:

mesonbuild/build.py

@@ -798,8 +798,8 @@ class BuildTarget():
         else:
             self.extra_args[language] = args
 
-    def get_aliaslist(self):
+    def get_aliases(self):
-        return []
+        return {}
 
     def get_clike_dynamic_linker(self):
         '''
@@ -1029,7 +1029,7 @@ class SharedLibrary(BuildTarget):
         First we determine the filename template (self.filename_tpl), then we
         set the output filename (self.filename).
 
-        The template is needed while creating aliases (self.get_aliaslist),
+        The template is needed while creating aliases (self.get_aliases),
         which are needed while generating .so shared libraries for Linux.
 
         Besides this, there's also the import library name, which is only used
@@ -1175,25 +1175,30 @@ class SharedLibrary(BuildTarget):
     def get_all_link_deps(self):
         return [self] + self.get_transitive_link_deps()
 
-    def get_aliaslist(self):
+    def get_aliases(self):
         """
         If the versioned library name is libfoo.so.0.100.0, aliases are:
-        * libfoo.so.0 (soversion)
+        * libfoo.so.0 (soversion) -> libfoo.so.0.100.0
-        * libfoo.so (unversioned; for linking)
+        * libfoo.so (unversioned; for linking) -> libfoo.so.0
         """
+        aliases = {}
         # Aliases are only useful with .so libraries. Also if the .so library
         # ends with .so (no versioning), we don't need aliases.
         if self.suffix != 'so' or self.filename.endswith('.so'):
-            return []
+            return {}
-        # Unversioned alias: libfoo.so
+        # If ltversion != soversion we create an soversion alias:
-        aliases = [self.basic_filename_tpl.format(self)]
+        # libfoo.so.0 -> libfoo.so.0.100.0
-        # If ltversion != soversion we create an soversion alias: libfoo.so.X
         if self.ltversion and self.ltversion != self.soversion:
             if not self.soversion:
                 # This is done in self.process_kwargs()
                 raise AssertionError('BUG: If library version is defined, soversion must have been defined')
             alias_tpl = self.filename_tpl.replace('ltversion', 'soversion')
-            aliases.append(alias_tpl.format(self))
+            ltversion_filename = alias_tpl.format(self)
+            aliases[ltversion_filename] = self.filename
+        else:
+            ltversion_filename = self.filename
+        # Unversioned alias: libfoo.so -> libfoo.so.0
+        aliases[self.basic_filename_tpl.format(self)] = ltversion_filename
         return aliases
 
     def type_suffix(self):

mesonbuild/modules/rpm.py

@@ -55,7 +55,7 @@ class RPMModule:
                 files.add('%%{_bindir}/%s' % target.get_filename())
             elif isinstance(target, build.SharedLibrary) and target.need_install:
                 files.add('%%{_libdir}/%s' % target.get_filename())
-                for alias in target.get_aliaslist():
+                for alias in target.get_aliases():
                     if alias.endswith('.so'):
                         files_devel.add('%%{_libdir}/%s' % alias)
                     else:

mesonbuild/scripts/meson_install.py

@@ -222,14 +222,14 @@ def install_targets(d):
         else:
             raise RuntimeError('Unknown file type for {!r}'.format(fname))
         printed_symlink_error = False
-        for alias in aliases:
+        for alias, to in aliases.items():
             try:
                 symlinkfilename = os.path.join(outdir, alias)
                 try:
                     os.unlink(symlinkfilename)
                 except FileNotFoundError:
                     pass
-                os.symlink(os.path.split(fname)[-1], symlinkfilename)
+                os.symlink(to, symlinkfilename)
                 append_to_log(symlinkfilename)
             except (NotImplementedError, OSError):
                 if not printed_symlink_error: