Deal with alternating headers

integrationtests.py

@@ -231,6 +231,57 @@ def testHitsSimple(self):
                 newHits = stats.numCacheHits()
             self.assertEqual(newHits, oldHits + 1)
 
+    def testAlternatingHeadersHit(self):
+        with cd(os.path.join(ASSETS_DIR, "hits-and-misses")), tempfile.TemporaryDirectory() as tempDir:
+            cache = clcache.Cache(tempDir)
+            customEnv = dict(os.environ, CLCACHE_DIR=tempDir)
+            baseCmd = CLCACHE_CMD + ["/nologo", "/EHsc", "/c"]
+
+            with cache.statistics as stats:
+                self.assertEqual(stats.numCacheHits(), 0)
+                self.assertEqual(stats.numCacheMisses(), 0)
+                self.assertEqual(stats.numCacheEntries(), 0)
+
+            # VERSION 1
+            with open('stable-source-with-alternating-header.h', 'w') as f:
+                f.write("#define VERSION 1\n")
+            subprocess.check_call(baseCmd + ["stable-source-with-alternating-header.cpp"], env=customEnv)
+
+            with cache.statistics as stats:
+                self.assertEqual(stats.numCacheHits(), 0)
+                self.assertEqual(stats.numCacheMisses(), 1)
+                self.assertEqual(stats.numCacheEntries(), 1)
+
+            # VERSION 2
+            with open('stable-source-with-alternating-header.h', 'w') as f:
+                f.write("#define VERSION 2\n")
+            subprocess.check_call(baseCmd + ["stable-source-with-alternating-header.cpp"], env=customEnv)
+
+            with cache.statistics as stats:
+                self.assertEqual(stats.numCacheHits(), 0)
+                self.assertEqual(stats.numCacheMisses(), 2)
+                self.assertEqual(stats.numCacheEntries(), 2)
+
+            # VERSION 1 again
+            with open('stable-source-with-alternating-header.h', 'w') as f:
+                f.write("#define VERSION 1\n")
+            subprocess.check_call(baseCmd + ["stable-source-with-alternating-header.cpp"], env=customEnv)
+
+            with cache.statistics as stats:
+                self.assertEqual(stats.numCacheHits(), 1)
+                self.assertEqual(stats.numCacheMisses(), 2)
+                self.assertEqual(stats.numCacheEntries(), 2)
+
+            # VERSION 2 again
+            with open('stable-source-with-alternating-header.h', 'w') as f:
+                f.write("#define VERSION 1\n")
+            subprocess.check_call(baseCmd + ["stable-source-with-alternating-header.cpp"], env=customEnv)
+
+            with cache.statistics as stats:
+                self.assertEqual(stats.numCacheHits(), 2)
+                self.assertEqual(stats.numCacheMisses(), 2)
+                self.assertEqual(stats.numCacheEntries(), 2)
+
 
 class TestPrecompiledHeaders(unittest.TestCase):
     def testSampleproject(self):

tests/integrationtests/hits-and-misses/.gitignore

@@ -0,0 +1,4 @@
+*.obj
+
+# written by the tests
+stable-source-with-alternating-header.h

tests/integrationtests/hits-and-misses/stable-source-with-alternating-header.cpp

@@ -0,0 +1,9 @@
+#include <iostream>
+
+#include "stable-source-with-alternating-header.h"
+
+int main()
+{
+    std::cout << "A C++ file we compile twice and expect a hit" << std::endl;
+    return 0;
+}