[clang][HeaderSearch] Consider all path separators equal

[sammccall]

clang/lib/Lex/HeaderSearch.cpp

1718

I think "consider all path separators equal" as in the patch description would be much clearer

[kadircet]

• Update comment

clang/lib/Lex/HeaderSearch.cpp

for (auto NI = path::begin(File), NE = path::end(File),
         unsigned PrefixLength = NI - path::begin(File);
         if (PrefixLength > BestPrefixLength) {
           BestPrefixLength = PrefixLength;
           BestSearchDir = I;
         }
         break;
       }
 
+      // Consider all path separators equal.
+      if (NI->size() == 1 && DI->size() == 1 &&
+          path::is_separator(NI->front()) && path::is_separator(DI->front()))
+        continue;
+
       if (*NI != *DI)
         break;
     }
   }
 
   if (IsSystem)
     *IsSystem = BestPrefixLength ? BestSearchDir >= SystemDirIdx : false;
   return path::convert_to_slash(File.drop_front(BestPrefixLength));
 }

clang/unittests/Lex/HeaderSearchTest.cpp

 
 #ifdef _WIN32
 TEST_F(HeaderSearchTest, BackSlash) {
   addSearchDir("C:\\x\\y\\");
   EXPECT_EQ(Search.suggestPathToFileForDiagnostics("C:\\x\\y\\z\\t",
                                                    /*WorkingDir=*/""),
             "z/t");
 }
+
+TEST_F(HeaderSearchTest, BackSlashWithDotDot) {
+  addSearchDir("..\\y");
+  EXPECT_EQ(Search.suggestPathToFileForDiagnostics("C:\\x\\y\\z\\t",
+                                                   /*WorkingDir=*/"C:/x/y/"),
+            "z/t");
+}
 #endif
 
 TEST_F(HeaderSearchTest, DotDotsWithAbsPath) {
   addSearchDir("/x/../y/");
   EXPECT_EQ(Search.suggestPathToFileForDiagnostics("/y/z",
                                                    /*WorkingDir=*/""),
             "z");
 }
 
 } // namespace
 } // namespace clang