[PATCH] D71727: [clang][Tooling] Prefer -x over -std when interpolating

[Kadir Cetinkaya via Phabricator via cfe-commits]

kadircet created this revision.
kadircet added a reviewer: sammccall.
Herald added subscribers: cfe-commits, usaxena95, ilya-biryukov.
Herald added a project: clang.

Currently interpolation logic prefers -std over -x. But the latter is a
more strong signal, so this patch inverts the order and only makes use of -std
if -x didn't exist.

Fixes https://github.com/clangd/clangd/issues/185

Thanks @sammccall for tracking this down!


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71727

Files:
  clang/lib/Tooling/InterpolatingCompilationDatabase.cpp
  clang/unittests/Tooling/CompilationDatabaseTest.cpp


Index: clang/unittests/Tooling/CompilationDatabaseTest.cpp
===================================================================
--- clang/unittests/Tooling/CompilationDatabaseTest.cpp
+++ clang/unittests/Tooling/CompilationDatabaseTest.cpp
@@ -749,6 +749,7 @@
   add("dir/foo.cpp", "-std=c++17");
   add("dir/bar.c", "");
   add("dir/baz.cee", "-x c");
+  add("dir/aux.cpp", "-std=c++17 -x objective-c++");
 
   // .h is ambiguous, so we add explicit language flags
   EXPECT_EQ(getCommand("foo.h"),
@@ -767,6 +768,9 @@
   Entries.erase(path(StringRef("dir/bar.c")));
   // Now we transfer across languages, so drop -std too.
   EXPECT_EQ(getCommand("foo.c"), "clang -D dir/foo.cpp");
+  // Prefer -x over -std when overriding language.
+  EXPECT_EQ(getCommand("aux.h"),
+            "clang -D dir/aux.cpp -x objective-c++-header -std=c++17");
 }
 
 TEST_F(InterpolateTest, Strip) {
Index: clang/lib/Tooling/InterpolatingCompilationDatabase.cpp
===================================================================
--- clang/lib/Tooling/InterpolatingCompilationDatabase.cpp
+++ clang/lib/Tooling/InterpolatingCompilationDatabase.cpp
@@ -191,7 +191,8 @@
                              OldArgs.data() + OldPos, OldArgs.data() + Pos);
     }
 
-    if (Std != LangStandard::lang_unspecified) // -std take precedence over -x
+    // Make use of -std iff -x was missing.
+    if (Type == types::TY_INVALID && Std != LangStandard::lang_unspecified)
       Type = toType(LangStandard::getLangStandardForKind(Std).getLanguage());
     Type = foldType(*Type);
     // The contract is to store None instead of TY_INVALID.


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