[flang] Allow a few irrelevant attributes, with warning

[klausler]

INTENT, VALUE, and OPTIONAL attributes apply only to dummy arguments. A couple older compilers accept them, usually with a warning, if they are applied to names that are not dummy arguments, and they show up in some older non-portable source code. Change these cases into stern warnings by default.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Author: Peter Klausler (klausler)

Changes

INTENT, VALUE, and OPTIONAL attributes apply only to dummy arguments. A couple older compilers accept them, usually with a warning, if they are applied to names that are not dummy arguments, and they show up in some older non-portable source code. Change these cases into stern warnings by default.

---

Full diff: https://github.com/llvm/llvm-project/pull/117374.diff

5 Files Affected:

• (modified) flang/include/flang/Common/Fortran-features.h (+2-1)
• (modified) flang/lib/Common/Fortran-features.cpp (+1)
• (modified) flang/lib/Semantics/check-declarations.cpp (+8-2)
• (modified) flang/test/Semantics/call14.f90 (+1-1)
• (modified) flang/test/Semantics/resolve58.f90 (+4-4)

diff --git a/flang/include/flang/Common/Fortran-features.h b/flang/include/flang/Common/Fortran-features.h
index c6ab846cce2fc0..9e3fd0dcca8e17 100644
--- a/flang/include/flang/Common/Fortran-features.h
+++ b/flang/include/flang/Common/Fortran-features.h
@@ -53,7 +53,8 @@ ENUM_CLASS(LanguageFeature, BackslashEscapes, OldDebugLines,
     NonBindCInteroperability, CudaManaged, CudaUnified,
     PolymorphicActualAllocatableOrPointerToMonomorphicDummy, RelaxedPureDummy,
     UndefinableAsynchronousOrVolatileActual, AutomaticInMainProgram, PrintCptr,
-    SavedLocalInSpecExpr, PrintNamelist, AssumedRankPassedToNonAssumedRank)
+    SavedLocalInSpecExpr, PrintNamelist, AssumedRankPassedToNonAssumedRank,
+    IgnoreIrrelevantAttributes)
 
 // Portability and suspicious usage warnings
 ENUM_CLASS(UsageWarning, Portability, PointerToUndefinable,
diff --git a/flang/lib/Common/Fortran-features.cpp b/flang/lib/Common/Fortran-features.cpp
index f47a4f17a6ba48..c86432874b8d83 100644
--- a/flang/lib/Common/Fortran-features.cpp
+++ b/flang/lib/Common/Fortran-features.cpp
@@ -43,6 +43,7 @@ LanguageFeatureControl::LanguageFeatureControl() {
   warnLanguage_.set(LanguageFeature::BadBranchTarget);
   warnLanguage_.set(LanguageFeature::HollerithPolymorphic);
   warnLanguage_.set(LanguageFeature::ListDirectedSize);
+  warnLanguage_.set(LanguageFeature::IgnoreIrrelevantAttributes);
   warnUsage_.set(UsageWarning::ShortArrayActual);
   warnUsage_.set(UsageWarning::FoldingException);
   warnUsage_.set(UsageWarning::FoldingAvoidsRuntimeCrash);
diff --git a/flang/lib/Semantics/check-declarations.cpp b/flang/lib/Semantics/check-declarations.cpp
index c9656d031b2e17..99c6e16c4260f1 100644
--- a/flang/lib/Semantics/check-declarations.cpp
+++ b/flang/lib/Semantics/check-declarations.cpp
@@ -320,8 +320,14 @@ void CheckHelper::Check(const Symbol &symbol) {
   if (symbol.attrs().HasAny({Attr::INTENT_IN, Attr::INTENT_INOUT,
           Attr::INTENT_OUT, Attr::OPTIONAL, Attr::VALUE}) &&
       !IsDummy(symbol)) {
-    messages_.Say(
-        "Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute"_err_en_US);
+    if (context_.IsEnabled(
+            common::LanguageFeature::IgnoreIrrelevantAttributes)) {
+      context_.Warn(common::LanguageFeature::IgnoreIrrelevantAttributes,
+          "Only a dummy argument should have an INTENT, VALUE, or OPTIONAL attribute"_warn_en_US);
+    } else {
+      messages_.Say(
+          "Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute"_err_en_US);
+    }
   } else if (symbol.attrs().test(Attr::VALUE)) {
     CheckValue(symbol, derived);
   }
diff --git a/flang/test/Semantics/call14.f90 b/flang/test/Semantics/call14.f90
index e586d4eebd2535..fba11d35790b2e 100644
--- a/flang/test/Semantics/call14.f90
+++ b/flang/test/Semantics/call14.f90
@@ -9,7 +9,7 @@ module m
   !ERROR: VALUE attribute may apply only to a dummy data object
   subroutine C863(notData,assumedSize,coarray,coarrayComponent,assumedRank,assumedLen)
     external :: notData
-    !ERROR: Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute
+    !WARNING: Only a dummy argument should have an INTENT, VALUE, or OPTIONAL attribute
     real, value :: notADummy
     value :: notData
     !ERROR: VALUE attribute may not apply to an assumed-size array
diff --git a/flang/test/Semantics/resolve58.f90 b/flang/test/Semantics/resolve58.f90
index 2e42eb157f5b50..7686de4898404d 100644
--- a/flang/test/Semantics/resolve58.f90
+++ b/flang/test/Semantics/resolve58.f90
@@ -69,12 +69,12 @@ subroutine s6()
 
   !ERROR: Implied-shape array 'local1' must be a named constant or a dummy argument
   real, dimension (*) :: local1
-  !ERROR: Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute
+  !WARNING: Only a dummy argument should have an INTENT, VALUE, or OPTIONAL attribute
   real, intent(in) :: local2
-  !ERROR: Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute
+  !WARNING: Only a dummy argument should have an INTENT, VALUE, or OPTIONAL attribute
   procedure(), intent(in) :: p1
-  !ERROR: Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute
+  !WARNING: Only a dummy argument should have an INTENT, VALUE, or OPTIONAL attribute
   real, optional :: local3
-  !ERROR: Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute
+  !WARNING: Only a dummy argument should have an INTENT, VALUE, or OPTIONAL attribute
   procedure(), optional :: p2
 end subroutine

[psteinfeld]

All builds and tests correctly and looks good.