From 85a263a6708f865bffe77c2fe9bb5e888c466709 Mon Sep 17 00:00:00 2001
From: Jussi Pakkanen <jpakkane@gmail.com>
Date: Sat, 17 Jun 2017 13:29:13 +0300
Subject: [PATCH 1/2] Failing test for -D dedupping.

---
 run_unittests.py                       |  8 ++++++++
 test cases/unit/10 d dedup/meson.build |  6 ++++++
 test cases/unit/10 d dedup/prog.c      | 14 ++++++++++++++
 3 files changed, 28 insertions(+)
 create mode 100644 test cases/unit/10 d dedup/meson.build
 create mode 100644 test cases/unit/10 d dedup/prog.c

diff --git a/run_unittests.py b/run_unittests.py
index a405b01be..7e3a2f11a 100755
--- a/run_unittests.py
+++ b/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):
     '''
diff --git a/test cases/unit/10 d dedup/meson.build b/test cases/unit/10 d dedup/meson.build
new file mode 100644
index 000000000..08f3a6c67
--- /dev/null
+++ b/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')
+
diff --git a/test cases/unit/10 d dedup/prog.c b/test cases/unit/10 d dedup/prog.c
new file mode 100644
index 000000000..505f12280
--- /dev/null
+++ b/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;
+}

From 1c34707aeeedfe499bf2101253788cb41e970383 Mon Sep 17 00:00:00 2001
From: Jussi Pakkanen <jpakkane@gmail.com>
Date: Sat, 17 Jun 2017 13:48:59 +0300
Subject: [PATCH 2/2] Preserve standalone -D arguments always.

---
 mesonbuild/compilers.py | 11 +++++++++++
 run_unittests.py        |  7 ++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/mesonbuild/compilers.py b/mesonbuild/compilers.py
index 2b54cc85c..6a9ad4f57 100644
--- a/mesonbuild/compilers.py
+++ b/mesonbuild/compilers.py
@@ -430,6 +430,17 @@ class CompilerArgs(list):
         to recursively search for symbols in the libraries. This is not needed
         with other linkers.
         '''
+
+        # A standalone argument must never be deduplicated because it is
+        # defined by what comes _after_ it. Thus dedupping this:
+        # -D FOO -D BAR
+        # would yield either
+        # -D FOO BAR
+        # or
+        # FOO -D BAR
+        # both of which are invalid.
+        if arg in cls.dedup2_prefixes:
+            return 0
         if arg in cls.dedup2_args or \
            arg.startswith(cls.dedup2_prefixes) or \
            arg.endswith(cls.dedup2_suffixes):
diff --git a/run_unittests.py b/run_unittests.py
index 7e3a2f11a..c21db089a 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -1225,9 +1225,10 @@ int main(int argc, char **argv) {
         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)
-
+        self.assertTrue('-D FOO -D BAR' in cmd or
+                        '"-D" "FOO" "-D" "BAR"' in cmd or
+                        '/D FOO /D BAR' in cmd or
+                        '"/D" "FOO" "/D" "BAR"' in cmd)
 
 
 class FailureTests(BasePlatformTests):