[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[kadir çetinkaya via cfe-commits]

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@@ -477,6 +486,109 @@ void DiagnosticsEngine::setSeverityForAll(diag::Flavor Flavor,
       setSeverity(Diag, Map, Loc);
 }
 
+namespace {
+class WarningsSpecialCaseList : public llvm::SpecialCaseList {
+public:
+  static std::unique_ptr<WarningsSpecialCaseList>
+  create(const llvm::MemoryBuffer &MB, std::string &Err) {
+    auto SCL = std::make_unique<WarningsSpecialCaseList>();
+    if (!SCL->createInternal(&MB, Err))
+      return nullptr;
+    return SCL;
+  }
+
+  // Section names refer to diagnostic groups, which cover multiple individual
+  // diagnostics. Expand diagnostic groups here to individual diagnostics.
+  // A diagnostic can have multiple diagnostic groups associated with it, we let
+  // the last section take precedence in such cases.
+  void processSections(DiagnosticsEngine &Diags) {
+    // Drop the default section introduced by special case list, we only support
+    // exact diagnostic group names.
+    Sections.erase("*");
+    // Make sure we iterate sections by their line numbers.
+    std::vector<std::pair<unsigned, const llvm::StringMapEntry<Section> *>>
+        LineAndSectionEntry;
+    LineAndSectionEntry.reserve(Sections.size());
+    for (const auto &Entry : Sections) {
+      LineAndSectionEntry.emplace_back(
+          Entry.second.SectionMatcher->Globs.at(Entry.first()).second, &Entry);
+    }
+    llvm::sort(LineAndSectionEntry);
+    static constexpr auto kFlavor = clang::diag::Flavor::WarningOrError;
+    for (const auto &[_, SectionEntry] : LineAndSectionEntry) {
+      SmallVector<diag::kind, 256> GroupDiags;
+      llvm::StringRef DiagGroup = SectionEntry->getKey();
+      if (Diags.getDiagnosticIDs()->getDiagnosticsInGroup(kFlavor, DiagGroup,
+                                                          GroupDiags)) {
+        StringRef Suggestion =
+            DiagnosticIDs::getNearestOption(kFlavor, DiagGroup);
+        Diags.Report(diag::warn_unknown_diag_option)
+            << static_cast<unsigned>(kFlavor) << DiagGroup
+            << !Suggestion.empty() << Suggestion;
+        continue;
+      }
+      for (diag::kind D : GroupDiags)
+        DiagToSection[D] = &SectionEntry->getValue();
+    }
+  }
+
+  bool isDiagSuppressed(diag::kind DiagId, llvm::StringRef FilePath) const {
+    auto Section = DiagToSection.find(DiagId);
+    if (Section == DiagToSection.end())
+      return false;
+    auto &DiagEntries = Section->second->Entries;
+    auto SrcEntries = DiagEntries.find("src");
+    if (SrcEntries == DiagEntries.end())
+      return false;
+    return globsMatches(SrcEntries->second, FilePath);
+  }
+
+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(llvm::StringMap<Matcher> CategoriesToMatchers,
+                    llvm::StringRef FilePath) const {
+    llvm::StringRef LongestMatch;
+    bool LongestIsPositive = false;
+    for (const auto &[Category, Matcher] : CategoriesToMatchers) {
+      bool IsPositive = Category != "emit";
+      for (const auto &[Pattern, Glob] : Matcher.Globs) {
----------------
kadircet wrote:

i am glad you asked :P

I was also thinking about that, but I don't think we benefit a lot from that here. As once we got a match, any shorter pattern is quite cheap, we just check the size and skip (don't try to match).

Sorting here, instead of looping would be worse. We need to make sure that sort happens while we're constructing the globs. But rest of the speical-case-list actually match entries in line order, and which line has matched is observable by the users. So this will be a breaking change for them.

Hence I'd rather keep it like this for now, and optimize later on if this turns out to be a big performance penalty, if that's fine with you as well.

https://github.com/llvm/llvm-project/pull/112517