Deduplicate command line arguments. Slight improvement to #671.

mesonbuild/backend/backends.py

@@ -630,3 +630,24 @@ class Backend():
         for s in self.build.postconf_scripts:
             cmd = s['exe'].get_command() + s['args']
             subprocess.check_call(cmd, env=child_env)
+
+    # Subprojects of subprojects may cause the same dep args to be used
+    # multiple times. Remove duplicates here. Note that we can't dedup
+    # libraries based on name alone, because "-lfoo -lbar -lfoo" is 
+    # a completely valid (though pathological) sequence and removing the
+    # latter may fail. Usually only applies to static libs, though.
+    def dedup_arguments(self, commands):
+        includes = {}
+        final_commands = []
+        previous = '-fsuch_arguments=woof'
+        for c in commands:
+            if c.startswith(('-I' '-L', '/LIBPATH')):
+                if c in includes:
+                    continue
+                includes[c] = True
+            if previous == c:
+                continue
+            previous = c
+            final_commands.append(c)
+        return final_commands
+                                                  

mesonbuild/backend/ninjabackend.py

@@ -1674,6 +1674,7 @@ rule FORTRAN_DEP_HACK
             element.add_orderdep(d)
         element.add_orderdep(pch_dep)
         element.add_orderdep(extra_orderdeps)
+        commands = self.dedup_arguments(commands)
         for i in self.get_fortran_orderdeps(target, compiler):
             element.add_orderdep(i)
         element.add_item('DEPFILE', dep_file)
@@ -1836,7 +1837,7 @@ rule FORTRAN_DEP_HACK
         custom_target_libraries = self.get_custom_target_provided_libraries(target)
         commands += extra_args
         commands += custom_target_libraries
-        commands = linker.unix_link_flags_to_native(commands)
+        commands = linker.unix_link_flags_to_native(self.dedup_arguments(commands))
         dep_targets = [self.get_dependency_filename(t) for t in dependencies]
         dep_targets += [os.path.join(self.environment.source_dir,
                                      target.subdir, t) for t in target.link_depends]