Add integration test for MSVC preprocessing bug

.github/workflows/integration-tests.yml

@@ -389,6 +389,11 @@ jobs:
           $SCCACHE_EXE --show-stats
           $SCCACHE_EXE --show-stats | grep -e "Cache hits\s*[1-9]"
 
+      - name: Compile MSVC - Proprocessing Compiler Bug
+        shell: bash
+        working-directory: ./tests/msvc-preprocessing
+        run: cl "@args.rsp"
+
       - name: Stop Server
         if: success() || failure()
         shell: bash

tests/msvc-preprocessing/args.rsp

@@ -0,0 +1 @@
+foo.cpp -Fofoo.o -W4 -WX -Wall

tests/msvc-preprocessing/foo.cpp

@@ -0,0 +1,15 @@
+// This tests sccache's ability to handle a known bug in cl.exe
+// More information: https://github.com/mozilla/sccache/issues/1725
+__pragma(warning(push))
+__pragma(warning(disable: 4668))
+// cl.exe during compilation will correctly ignore 4668 here (undefined define)
+// during preprocessing, it will not ignore 4668
+// sccache must explicitly ignore this warning when preprocessing (to figure out the cache key)
+#if UNDEFINED_MACRO_TRIGGERING_C4668
+#error "This error should be unreachable"
+#endif
+__pragma(warning(pop))
+
+int main() {
+  return 0;
+}