[clang] [Clang] Silently ignore unknown warnings in `--warning-suppression-mappings` (PR #124141)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: James Y Knight (jyknight)

<details>
<summary>Changes</summary>

This allows the same file to be used on multiple Clang versions, without generating output spam.

Also disable parsing of the suppressions file in the Driver, where it's not needed. This was previously causing the diagnostics to be emitted twice, as the file was being parsed twice.

I'll also note that if we do ever wish to emit non-fatal diagnostics from parsing this file, it'll need more: the code deleted here emitted warnings which were not possible for a user to disable, since the suppression file is parsed _before_ the diagnostic state has been setup.

---
Full diff: https://github.com/llvm/llvm-project/pull/124141.diff


4 Files Affected:

- (modified) clang/lib/Basic/Diagnostic.cpp (+3-5) 
- (modified) clang/test/Misc/Inputs/suppression-mapping.txt (+4) 
- (modified) clang/tools/driver/driver.cpp (+3) 
- (modified) clang/unittests/Basic/DiagnosticTest.cpp (+1-2) 


``````````diff
diff --git a/clang/lib/Basic/Diagnostic.cpp b/clang/lib/Basic/Diagnostic.cpp
index ae71758bc81e03..55efd5ffafcece 100644
--- a/clang/lib/Basic/Diagnostic.cpp
+++ b/clang/lib/Basic/Diagnostic.cpp
@@ -547,11 +547,9 @@ void WarningsSpecialCaseList::processSections(DiagnosticsEngine &Diags) {
     StringRef DiagGroup = SectionEntry->getKey();
     if (Diags.getDiagnosticIDs()->getDiagnosticsInGroup(
             WarningFlavor, DiagGroup, GroupDiags)) {
-      StringRef Suggestion =
-          DiagnosticIDs::getNearestOption(WarningFlavor, DiagGroup);
-      Diags.Report(diag::warn_unknown_diag_option)
-          << static_cast<unsigned>(WarningFlavor) << DiagGroup
-          << !Suggestion.empty() << Suggestion;
+      // If a diagnostic group name is unknown, simply ignore the
+      // suppressions. This allows use of a single suppression file on multiple
+      // versions of clang.
       continue;
     }
     for (diag::kind Diag : GroupDiags)
diff --git a/clang/test/Misc/Inputs/suppression-mapping.txt b/clang/test/Misc/Inputs/suppression-mapping.txt
index abe4fde0c265d5..cea8c50daee1c5 100644
--- a/clang/test/Misc/Inputs/suppression-mapping.txt
+++ b/clang/test/Misc/Inputs/suppression-mapping.txt
@@ -11,3 +11,7 @@ src:*foo/*=emit
 [format=2]
 src:*
 src:*foo/*=emit
+
+# A warning group that clang doesn't know about should be silently ignored.
+[barglegunk]
+src:*
diff --git a/clang/tools/driver/driver.cpp b/clang/tools/driver/driver.cpp
index 74923247b7ee16..c68367c177910c 100644
--- a/clang/tools/driver/driver.cpp
+++ b/clang/tools/driver/driver.cpp
@@ -319,6 +319,9 @@ int clang_main(int Argc, char **Argv, const llvm::ToolContext &ToolContext) {
   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts =
       CreateAndPopulateDiagOpts(Args);
 
+  // The _driver_ (vs cc1) diagnostics engine shouldn't bother to load a suppression file.
+  DiagOpts->DiagnosticSuppressionMappingsFile = "";
+
   TextDiagnosticPrinter *DiagClient
     = new TextDiagnosticPrinter(llvm::errs(), &*DiagOpts);
   FixupDiagPrefixExeName(DiagClient, ProgName);
diff --git a/clang/unittests/Basic/DiagnosticTest.cpp b/clang/unittests/Basic/DiagnosticTest.cpp
index e03d9a464df7f9..6c431ed81c4919 100644
--- a/clang/unittests/Basic/DiagnosticTest.cpp
+++ b/clang/unittests/Basic/DiagnosticTest.cpp
@@ -253,8 +253,7 @@ TEST_F(SuppressionMappingTest, UnknownDiagName) {
   FS->addFile("foo.txt", /*ModificationTime=*/{},
               llvm::MemoryBuffer::getMemBuffer("[non-existing-warning]"));
   clang::ProcessWarningOptions(Diags, Diags.getDiagnosticOptions(), *FS);
-  EXPECT_THAT(diags(), ElementsAre(WithMessage(
-                           "unknown warning option 'non-existing-warning'")));
+  EXPECT_THAT(diags(), IsEmpty());
 }
 
 TEST_F(SuppressionMappingTest, SuppressesGroup) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/124141