Can link against custom targets. Closes #4908.

4 files changed, 35 insertions, 3 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index be181a8..b62438e 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -211,6 +211,10 @@ class Backend:
             return os.path.join(self.get_target_dir(target), link_lib)
         elif isinstance(target, build.StaticLibrary):
             return os.path.join(self.get_target_dir(target), target.get_filename())
+        elif isinstance(target, build.CustomTarget):
+            if not target.is_linkable_target():
+                raise MesonException('Tried to link against custom target "%s", which is not linkable.' % target.name)
+            return os.path.join(self.get_target_dir(target), target.get_filename())
         elif isinstance(target, build.Executable):
             if target.import_filename:
                 return os.path.join(self.get_target_dir(target), target.get_import_filename())
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 20f0cdb..eb8e60c 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -567,6 +567,8 @@ class BuildTarget(Target):
         if self.link_targets or self.link_whole_targets:
             extra = set()
             for t in itertools.chain(self.link_targets, self.link_whole_targets):
+                if isinstance(t, CustomTarget):
+                    continue # We can't know anything about these.
                 for name, compiler in t.compilers.items():
                     if name in clink_langs:
                         extra.add((name, compiler))
@@ -1062,7 +1064,7 @@ You probably should put it in link_with instead.''')
                 msg = "Can't link non-PIC static library {!r} into shared library {!r}. ".format(t.name, self.name)
                 msg += "Use the 'pic' option to static_library to build with PIC."
                 raise InvalidArguments(msg)
-            if self.is_cross != t.is_cross:
+            if not isinstance(t, CustomTarget) and self.is_cross != t.is_cross:
                 raise InvalidArguments('Tried to mix cross built and native libraries in target {!r}'.format(self.name))
             self.link_targets.append(t)
 
@@ -1149,6 +1151,8 @@ You probably should put it in link_with instead.''')
         # Check if any of the internal libraries this target links to were
         # written in this language
         for link_target in itertools.chain(self.link_targets, self.link_whole_targets):
+            if isinstance(link_target, CustomTarget):
+                continue
             for language in link_target.compilers:
                 if language not in langs:
                     langs.append(language)
@@ -2090,6 +2094,19 @@ class CustomTarget(Target):
                 raise InvalidArguments('Substitution in depfile for custom_target that does not have an input file.')
             return self.depfile
 
+    def is_linkable_target(self):
+        if len(self.outputs) != 1:
+            return False
+        suf = os.path.splitext(self.outputs[0])[-1]
+        if suf == '.a' or suf == '.dll' or suf == '.lib' or suf == '.so':
+            return True
+
+    def get_link_dep_subdirs(self):
+        return OrderedSet()
+
+    def get_all_link_deps(self):
+        return []
+
     def type_suffix(self):
         return "@cus"
 
diff --git a/test cases/common/216 link custom/meson.build b/test cases/common/216 link custom/meson.build
index dc01354..a1923b9 100644
--- a/test cases/common/216 link custom/meson.build
+++ b/test cases/common/216 link custom/meson.build
@@ -16,5 +16,10 @@ clib = custom_target('linkcustom',
             '-o', '@OUTPUT@',
             '--private-dir', '@PRIVATE_DIR@'] + cc.cmd_array())
 
-#exe = executable('prog', 'prog.c', link_with: clib)
-#test('linkcustom', exe)
+exe = executable('prog', 'prog.c', link_with: clib)
+test('linkcustom', exe)
+
+d = declare_dependency(link_with: clib)
+
+exe2 = executable('prog2', 'prog.c', dependencies: d)
+test('linkcustom2', exe2)
diff --git a/test cases/common/216 link custom/prog.c b/test cases/common/216 link custom/prog.c
new file mode 100644
index 0000000..eaede6d
--- /dev/null
+++ b/test cases/common/216 link custom/prog.c
@@ -0,0 +1,6 @@
+void flob();
+
+int main(int argc, char **argv) {
+    flob();
+    return 0;
+}