[clang] Clang multi-match behavior of WarningSuppressionMappings

clang/docs/ReleaseNotes.rst

@@ -69,6 +69,8 @@ Potentially Breaking Changes
   call the member ``operator delete`` instead of the expected global
   delete operator. The old behavior is retained under ``-fclang-abi-compat=21``
   flag.
+- Clang warning suppressions file, ``--warning-suppression-mappings=``, now will
+  use the last matching entry instead of the longest one.
 
 C/C++ Language Potentially Breaking Changes
 -------------------------------------------

clang/docs/WarningSuppressionMappings.rst

@@ -63,7 +63,7 @@ Format
 Warning suppression mappings uses the same format as
 :doc:`SanitizerSpecialCaseList`.
 
-Sections describe which diagnostic group's behaviour to change, e.g.
+Sections describe which diagnostic group's behavior to change, e.g.
 ``[unused]``. When a diagnostic is matched by multiple sections, the latest
 section takes precedence.
 
@@ -76,7 +76,7 @@ Source files are matched against these globs either:
 - as paths relative to the current working directory
 - as absolute paths.
 
-When a source file matches multiple globs in a section, the longest one takes
+When a source file matches multiple globs in a section, the last one takes
 precedence.
 
 .. code-block:: bash

clang/include/clang/Basic/Diagnostic.h

@@ -971,7 +971,7 @@ class DiagnosticsEngine : public RefCountedBase<DiagnosticsEngine> {
   /// diagnostics in specific files.
   /// Mapping file is expected to be a special case list with sections denoting
   /// diagnostic groups and `src` entries for globs to suppress. `emit` category
-  /// can be used to disable suppression. Longest glob that matches a filepath
+  /// can be used to disable suppression. THe last glob that matches a filepath
   /// takes precedence. For example:
   ///   [unused]
   ///   src:clang/*

clang/lib/Basic/Diagnostic.cpp

@@ -517,12 +517,6 @@ class WarningsSpecialCaseList : public llvm::SpecialCaseList {
                         const SourceManager &SM) const;
 
 private:
-  // Find the longest glob pattern that matches FilePath amongst
-  // CategoriesToMatchers, return true iff the match exists and belongs to a
-  // positive category.
-  bool globsMatches(const llvm::StringMap<Matcher> &CategoriesToMatchers,
-                    StringRef FilePath) const;
-
   llvm::DenseMap<diag::kind, const Section *> DiagToSection;
 };
 } // namespace
@@ -584,43 +578,26 @@ void DiagnosticsEngine::setDiagSuppressionMapping(llvm::MemoryBuffer &Input) {
 bool WarningsSpecialCaseList::isDiagSuppressed(diag::kind DiagId,
                                                SourceLocation DiagLoc,
                                                const SourceManager &SM) const {
+  PresumedLoc PLoc = SM.getPresumedLoc(DiagLoc);
+  if (!PLoc.isValid())
+    return false;
   const Section *DiagSection = DiagToSection.lookup(DiagId);
   if (!DiagSection)
     return false;
-  const SectionEntries &EntityTypeToCategories = DiagSection->Entries;
-  auto SrcEntriesIt = EntityTypeToCategories.find("src");
-  if (SrcEntriesIt == EntityTypeToCategories.end())
+
+  StringRef F = llvm::sys::path::remove_leading_dotslash(PLoc.getFilename());
+
+  unsigned SuppressLineNo =
+      llvm::SpecialCaseList::inSectionBlame(DiagSection->Entries, "src", F, "");
+  if (!SuppressLineNo)
     return false;
-  const llvm::StringMap<llvm::SpecialCaseList::Matcher> &CategoriesToMatchers =
-      SrcEntriesIt->getValue();
-  // We also use presumed locations here to improve reproducibility for
-  // preprocessed inputs.
-  if (PresumedLoc PLoc = SM.getPresumedLoc(DiagLoc); PLoc.isValid())
-    return globsMatches(
-        CategoriesToMatchers,
-        llvm::sys::path::remove_leading_dotslash(PLoc.getFilename()));
-  return false;
-}
 
-bool WarningsSpecialCaseList::globsMatches(
-    const llvm::StringMap<Matcher> &CategoriesToMatchers,
-    StringRef FilePath) const {
-  StringRef LongestMatch;
-  bool LongestIsPositive = false;
-  for (const auto &Entry : CategoriesToMatchers) {
-    StringRef Category = Entry.getKey();
-    const llvm::SpecialCaseList::Matcher &Matcher = Entry.getValue();
-    bool IsPositive = Category != "emit";
-    for (const auto &Glob : Matcher.Globs) {
-      if (Glob->Name.size() < LongestMatch.size())
-        continue;
-      if (!Glob->Pattern.match(FilePath))
-        continue;
-      LongestMatch = Glob->Name;
-      LongestIsPositive = IsPositive;
-    }
-  }
-  return LongestIsPositive;
+  unsigned EmitLineNo = llvm::SpecialCaseList::inSectionBlame(
+      DiagSection->Entries, "src", F, "emit");
+  if (!EmitLineNo)
+    return true;
+
+  return SuppressLineNo > EmitLineNo;
 }
 
 bool DiagnosticsEngine::isSuppressedViaMapping(diag::kind DiagId,

clang/unittests/Basic/DiagnosticTest.cpp

@@ -294,7 +294,7 @@ TEST_F(SuppressionMappingTest, EmitCategoryIsExcluded) {
                                             locForFile("foo.cpp")));
 }
 
-TEST_F(SuppressionMappingTest, LongestMatchWins) {
+TEST_F(SuppressionMappingTest, LastMatchWins) {
   llvm::StringLiteral SuppressionMappingFile = R"(
   [unused]
   src:*clang/*
@@ -327,10 +327,8 @@ TEST_F(SuppressionMappingTest, LongShortMatch) {
 
   EXPECT_TRUE(Diags.isSuppressedViaMapping(diag::warn_unused_function,
                                            locForFile("test/t1.cpp")));
-
-  // FIXME: This is confusing.
-  EXPECT_TRUE(Diags.isSuppressedViaMapping(diag::warn_unused_function,
-                                           locForFile("lld/test/t2.cpp")));
+  EXPECT_FALSE(Diags.isSuppressedViaMapping(diag::warn_unused_function,
+                                            locForFile("lld/test/t2.cpp")));
 }
 
 TEST_F(SuppressionMappingTest, ShortLongMatch) {