Failing test for -D dedupping.

run_unittests.py

@@ -1221,6 +1221,14 @@ int main(int argc, char **argv) {
             for path in rpath.split(':'):
                 self.assertTrue(path.startswith('$ORIGIN'), msg=(each, path))
 
+    def test_dash_d_dedup(self):
+        testdir = os.path.join(self.unit_test_dir, '10 d dedup')
+        self.init(testdir)
+        cmd = self.get_compdb()[0]['command']
+        self.assertTrue('-D FOO -D BAR' in cmd or \
+                        '/D FOO /D BAR' in cmd)
+
+
 
 class FailureTests(BasePlatformTests):
     '''

test cases/unit/10 d dedup/meson.build

@@ -0,0 +1,6 @@
+project('d dedup', 'c')
+
+add_project_arguments('-D', 'FOO', '-D', 'BAR', language : 'c')
+
+executable('prog', 'prog.c')
+

test cases/unit/10 d dedup/prog.c

@@ -0,0 +1,14 @@
+#include<stdio.h>
+
+#ifndef FOO
+#error FOO is not defined.
+#endif
+
+#ifndef BAR
+#error BAR is not defined.
+#endif
+
+int main(int argc, char **argv) {
+    printf("All is well.\n");
+    return 0;
+}