[flang][CLI] Have the CLI hint the flag to disable a warning

flang/include/flang/Parser/message.h

@@ -292,7 +292,8 @@ class Message : public common::ReferenceCounted<Message> {
   std::optional<ProvenanceRange> GetProvenanceRange(
       const AllCookedSources &) const;
   void Emit(llvm::raw_ostream &, const AllCookedSources &,
-      bool echoSourceLine = true) const;
+      bool echoSourceLine = true,
+      const common::LanguageFeatureControl *hintFlags = nullptr) const;
 
   // If this Message or any of its attachments locates itself via a CharBlock,
   // replace its location with the corresponding ProvenanceRange.
@@ -352,7 +353,8 @@ class Messages {
   void Copy(const Messages &);
   void ResolveProvenances(const AllCookedSources &);
   void Emit(llvm::raw_ostream &, const AllCookedSources &,
-      bool echoSourceLines = true) const;
+      bool echoSourceLines = true,
+      const common::LanguageFeatureControl *hintFlags = nullptr) const;
   void AttachTo(Message &, std::optional<Severity> = std::nullopt);
   bool AnyFatalError() const;
 

flang/include/flang/Support/Fortran-features.h

@@ -156,14 +156,13 @@ class LanguageFeatureControl {
 private:
   // Map from Cli syntax of language features and usage warnings to their enum
   // values.
-  std::unordered_map<std::string, std::variant<LanguageFeature, UsageWarning>>
-      cliOptions_;
+  std::unordered_map<std::string, LanguageFeatureOrWarning> cliOptions_;
   // These two arrays map the enum values to their cannonical Cli spellings.
   // Since each of the CanonicalSpelling is a string in the domain of the map
   // above we just use a view of the string instead of another copy.
-  std::array<std::string_view, LanguageFeature_enumSize>
+  std::array<std::string, LanguageFeature_enumSize>
       languageFeatureCliCanonicalSpelling_;
-  std::array<std::string_view, UsageWarning_enumSize>
+  std::array<std::string, UsageWarning_enumSize>
       usageWarningCliCanonicalSpelling_;
   LanguageFeatures disable_;
   LanguageFeatures warnLanguage_;

flang/lib/Frontend/FrontendAction.cpp

@@ -171,7 +171,10 @@ bool FrontendAction::runParse(bool emitMessages) {
   if (emitMessages) {
     // Report any non-fatal diagnostics from getParsing now rather than
     // combining them with messages from semantics.
-    ci.getParsing().messages().Emit(llvm::errs(), ci.getAllCookedSources());
+    const common::LanguageFeatureControl &features{
+        ci.getInvocation().getFortranOpts().features};
+    ci.getParsing().messages().Emit(llvm::errs(), ci.getAllCookedSources(),
+                                    /*echoSourceLine=*/true, &features);
   }
   return true;
 }
@@ -223,14 +226,17 @@ bool FrontendAction::generateRtTypeTables() {
 
 template <unsigned N>
 bool FrontendAction::reportFatalErrors(const char (&message)[N]) {
+  const common::LanguageFeatureControl &features{
+      instance->getInvocation().getFortranOpts().features};
   if (!instance->getParsing().messages().empty() &&
       (instance->getInvocation().getWarnAsErr() ||
        instance->getParsing().messages().AnyFatalError())) {
     const unsigned diagID = instance->getDiagnostics().getCustomDiagID(
         clang::DiagnosticsEngine::Error, message);
     instance->getDiagnostics().Report(diagID) << getCurrentFileOrBufferName();
     instance->getParsing().messages().Emit(llvm::errs(),
-                                           instance->getAllCookedSources());
+                                           instance->getAllCookedSources(),
+                                           /*echoSourceLines=*/true, &features);
     return true;
   }
   if (instance->getParsing().parseTree().has_value() &&
@@ -240,7 +246,8 @@ bool FrontendAction::reportFatalErrors(const char (&message)[N]) {
         clang::DiagnosticsEngine::Error, message);
     instance->getDiagnostics().Report(diagID) << getCurrentFileOrBufferName();
     instance->getParsing().messages().Emit(llvm::errs(),
-                                           instance->getAllCookedSources());
+                                           instance->getAllCookedSources(),
+                                           /*echoSourceLine=*/true, &features);
     instance->getParsing().EmitMessage(
         llvm::errs(), instance->getParsing().finalRestingPlace(),
         "parser FAIL (final position)", "error: ", llvm::raw_ostream::RED);

flang/lib/Parser/message.cpp

@@ -273,14 +273,36 @@ static llvm::raw_ostream::Colors PrefixColor(Severity severity) {
   return llvm::raw_ostream::SAVEDCOLOR;
 }
 
+static std::string HintLanguageControlFlag(
+    const common::LanguageFeatureControl *hintFlagPtr,
+    std::optional<common::LanguageFeature> feature,
+    std::optional<common::UsageWarning> warning) {
+  if (hintFlagPtr) {
+    std::string flag;
+    if (warning) {
+      flag = hintFlagPtr->getDefaultCliSpelling(*warning);
+    } else if (feature) {
+      flag = hintFlagPtr->getDefaultCliSpelling(*feature);
+    }
+    if (!flag.empty()) {
+      return " [-W" + flag + "]";
+    }
+  }
+  return "";
+}
+
 static constexpr int MAX_CONTEXTS_EMITTED{2};
 static constexpr bool OMIT_SHARED_CONTEXTS{true};
 
 void Message::Emit(llvm::raw_ostream &o, const AllCookedSources &allCooked,
-    bool echoSourceLine) const {
+    bool echoSourceLine,
+    const common::LanguageFeatureControl *hintFlagPtr) const {
   std::optional<ProvenanceRange> provenanceRange{GetProvenanceRange(allCooked)};
   const AllSources &sources{allCooked.allSources()};
-  sources.EmitMessage(o, provenanceRange, ToString(), Prefix(severity()),
+  const std::string text{ToString()};
+  const std::string hint{
+      HintLanguageControlFlag(hintFlagPtr, languageFeature_, usageWarning_)};
+  sources.EmitMessage(o, provenanceRange, text + hint, Prefix(severity()),
       PrefixColor(severity()), echoSourceLine);
   // Refers to whether the attachment in the loop below is a context, but can't
   // be declared inside the loop because the previous iteration's
@@ -430,7 +452,8 @@ void Messages::ResolveProvenances(const AllCookedSources &allCooked) {
 }
 
 void Messages::Emit(llvm::raw_ostream &o, const AllCookedSources &allCooked,
-    bool echoSourceLines) const {
+    bool echoSourceLines,
+    const common::LanguageFeatureControl *hintFlagPtr) const {
   std::vector<const Message *> sorted;
   for (const auto &msg : messages_) {
     sorted.push_back(&msg);
@@ -443,7 +466,7 @@ void Messages::Emit(llvm::raw_ostream &o, const AllCookedSources &allCooked,
       // Don't emit two identical messages for the same location
       continue;
     }
-    msg->Emit(o, allCooked, echoSourceLines);
+    msg->Emit(o, allCooked, echoSourceLines, hintFlagPtr);
     lastMsg = msg;
   }
 }

flang/lib/Semantics/semantics.cpp

@@ -655,8 +655,10 @@ bool Semantics::Perform() {
 void Semantics::EmitMessages(llvm::raw_ostream &os) {
   // Resolve the CharBlock locations of the Messages to ProvenanceRanges
   // so messages from parsing and semantics are intermixed in source order.
+  const common::LanguageFeatureControl &features{context_.languageFeatures()};
   context_.messages().ResolveProvenances(context_.allCookedSources());
-  context_.messages().Emit(os, context_.allCookedSources());
+  context_.messages().Emit(
+      os, context_.allCookedSources(), /*echoSourceLine=*/true, &features);
 }
 
 void SemanticsContext::DumpSymbols(llvm::raw_ostream &os) {

flang/lib/Support/Fortran-features.cpp

@@ -59,15 +59,15 @@ LanguageFeatureControl::LanguageFeatureControl() {
     std::string cliOption{details::CamelCaseToLowerCaseHyphenated(name)};
     cliOptions_.insert({cliOption, {feature}});
     languageFeatureCliCanonicalSpelling_[EnumToInt(feature)] =
-        std::string_view{cliOption};
+        std::move(cliOption);
   });
 
   ForEachUsageWarning([&](auto warning) {
     std::string_view name{Fortran::common::EnumToString(warning)};
     std::string cliOption{details::CamelCaseToLowerCaseHyphenated(name)};
     cliOptions_.insert({cliOption, {warning}});
     usageWarningCliCanonicalSpelling_[EnumToInt(warning)] =
-        std::string_view{cliOption};
+        std::move(cliOption);
   });
 
   // These features must be explicitly enabled by command line options.
@@ -174,18 +174,16 @@ bool LanguageFeatureControl::EnableWarning(std::string_view input) {
 
 void LanguageFeatureControl::ReplaceCliCanonicalSpelling(
     LanguageFeature f, std::string input) {
-  std::string_view &old{languageFeatureCliCanonicalSpelling_[EnumToInt(f)]};
-  cliOptions_.erase(std::string{old});
-  languageFeatureCliCanonicalSpelling_[EnumToInt(f)] = input;
+  cliOptions_.erase(languageFeatureCliCanonicalSpelling_[EnumToInt(f)]);
   cliOptions_.insert({input, {f}});
+  languageFeatureCliCanonicalSpelling_[EnumToInt(f)] = std::move(input);
 }
 
 void LanguageFeatureControl::ReplaceCliCanonicalSpelling(
     UsageWarning w, std::string input) {
-  std::string_view &old{usageWarningCliCanonicalSpelling_[EnumToInt(w)]};
-  cliOptions_.erase(std::string{old});
-  usageWarningCliCanonicalSpelling_[EnumToInt(w)] = input;
+  cliOptions_.erase(usageWarningCliCanonicalSpelling_[EnumToInt(w)]);
   cliOptions_.insert({input, {w}});
+  usageWarningCliCanonicalSpelling_[EnumToInt(w)] = std::move(input);
 }
 
 std::vector<const char *> LanguageFeatureControl::GetNames(

flang/test/Evaluate/fold-dim.f90

@@ -11,7 +11,7 @@ module m
   logical, parameter :: test_a3 = dim(2., 1.) == 1.
   logical, parameter :: test_a4 = dim(2., -1.) == 3.
   logical, parameter :: test_a5 = dim(-1., 2.) == 0.
-  !WARN: warning: invalid argument on division
+  !WARN: warning: invalid argument on division [-Wfolding-exception]
   real, parameter :: nan = 0./0.
   logical, parameter :: test_a6 = dim(nan, 1.) /= dim(nan, 1.)
 end module

flang/test/Evaluate/fold-nearest.f90

@@ -19,16 +19,16 @@ module m1
   real, parameter :: negZero = sign(0., -1.)
   logical, parameter :: test_12 = nearest(negZero, 1.) == minSubnormal
   logical, parameter :: test_13 = nearest(negZero, -1.) == -minSubnormal
-  !WARN: warning: NEAREST: S argument is zero
+  !WARN: warning: NEAREST: S argument is zero [-Wfolding-value-checks]
   logical, parameter :: test_14 = nearest(0., negZero) == -minSubnormal
-  !WARN: warning: NEAREST: S argument is zero
+  !WARN: warning: NEAREST: S argument is zero [-Wfolding-value-checks]
   logical, parameter :: test_15 = nearest(negZero, 0.) == minSubnormal
   logical, parameter :: test_16 = nearest(tiny(1.),-1.) == 1.1754942E-38
   logical, parameter :: test_17 = nearest(tiny(1.),1.) == 1.1754945E-38
  contains
   subroutine subr(a)
     real, intent(in) :: a
-    !WARN: warning: NEAREST: S argument is zero
+    !WARN: warning: NEAREST: S argument is zero [-Wfolding-value-checks]
     print *, nearest(a, 0.)
   end
 end module
@@ -42,7 +42,7 @@ module m2
   logical, parameter :: test_2 = ieee_next_after(minSubnormal, -1.) == 0
   logical, parameter :: test_3 = ieee_next_after(1., 2.) == 1.0000001
   logical, parameter :: test_4 = ieee_next_after(1.0000001, -1.) == 1
-  !WARN: warning: division by zero
+  !WARN: warning: division by zero [-Wfolding-exception]
   real, parameter :: inf = 1. / 0.
   logical, parameter :: test_5 = ieee_next_after(inf, inf) == inf
   logical, parameter :: test_6 = ieee_next_after(inf, -inf) == h
@@ -54,12 +54,12 @@ module m2
   logical, parameter :: test_11 = ieee_next_after(1.9999999999999999999_10, 3.) == 2._10
 #endif
   logical, parameter :: test_12 = ieee_next_after(1., 1.) == 1.
-  !WARN: warning: invalid argument on division
+  !WARN: warning: invalid argument on division [-Wfolding-exception]
   real, parameter :: nan = 0. / 0.
-  !WARN: warning: IEEE_NEXT_AFTER intrinsic folding: arguments are unordered
+  !WARN: warning: IEEE_NEXT_AFTER intrinsic folding: arguments are unordered [-Wfolding-value-checks]
   real, parameter :: x13 = ieee_next_after(nan, nan)
   logical, parameter :: test_13 = .not. (x13 == x13)
-  !WARN: warning: IEEE_NEXT_AFTER intrinsic folding: arguments are unordered
+  !WARN: warning: IEEE_NEXT_AFTER intrinsic folding: arguments are unordered [-Wfolding-value-checks]
   real, parameter :: x14 = ieee_next_after(nan, 0.)
   logical, parameter :: test_14 = .not. (x14 == x14)
 end module
@@ -72,7 +72,7 @@ module m3
   logical, parameter :: test_2 = ieee_next_down(0.d0) == -minSubnormal
   logical, parameter :: test_3 = ieee_next_up(1.d0) == 1.0000000000000002d0
   logical, parameter :: test_4 = ieee_next_down(1.0000000000000002d0) == 1.d0
-  !WARN: warning: division by zero
+  !WARN: warning: division by zero [-Wfolding-exception]
   real(kind(0.d0)), parameter :: inf = 1.d0 / 0.d0
   logical, parameter :: test_5 = ieee_next_up(huge(0.d0)) == inf
   logical, parameter :: test_6 = ieee_next_down(-huge(0.d0)) == -inf
@@ -82,12 +82,12 @@ module m3
   logical, parameter :: test_10 = ieee_next_down(-inf) == -inf
   logical, parameter :: test_11 = ieee_next_up(1.9999999999999997d0) == 2.d0
   logical, parameter :: test_12 = ieee_next_down(2.d0) == 1.9999999999999997d0
-  !WARN: warning: invalid argument on division
+  !WARN: warning: invalid argument on division [-Wfolding-exception]
   real(kind(0.d0)), parameter :: nan = 0.d0 / 0.d0
-  !WARN: warning: IEEE_NEXT_UP intrinsic folding: argument is NaN
+  !WARN: warning: IEEE_NEXT_UP intrinsic folding: argument is NaN [-Wfolding-exception]
   real(kind(0.d0)), parameter :: x13 = ieee_next_up(nan)
   logical, parameter :: test_13 = .not. (x13 == x13)
-  !WARN: warning: IEEE_NEXT_DOWN intrinsic folding: argument is NaN
+  !WARN: warning: IEEE_NEXT_DOWN intrinsic folding: argument is NaN [-Wfolding-exception]
   real(kind(0.d0)), parameter :: x14 = ieee_next_down(nan)
   logical, parameter :: test_14 = .not. (x14 == x14)
 end module