[flang][frontend] warn when a volatile target is pointer associated with an non-volatile pointer (llvm#136778)

closes llvm#135805

Author: akuhlens

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

@@ -76,7 +76,7 @@ ENUM_CLASS(UsageWarning, Portability, PointerToUndefinable,
     MismatchingDummyProcedure, SubscriptedEmptyArray, UnsignedLiteralTruncation,
     CompatibleDeclarationsFromDistinctModules,
     NullActualForDefaultIntentAllocatable, UseAssociationIntoSameNameSubprogram,
-    HostAssociatedIntentOutInSpecExpr)
+    HostAssociatedIntentOutInSpecExpr, NonVolatilePointerToVolatile)
 
 using LanguageFeatures = EnumSet<LanguageFeature, LanguageFeature_enumSize>;
 using UsageWarnings = EnumSet<UsageWarning, UsageWarning_enumSize>;

flang/lib/Semantics/pointer-assignment.cpp

@@ -360,6 +360,20 @@ bool PointerAssignmentChecker::Check(const evaluate::Designator<T> &d) {
     } else {
       Say(std::get<MessageFormattedText>(*msg));
     }
+  }
+
+  // Show warnings after errors
+
+  // 8.5.20(3) A pointer should have the VOLATILE attribute if its target has
+  // the VOLATILE attribute
+  // 8.5.20(4) If an object has the VOLATILE attribute, then all of its
+  // subobjects also have the VOLATILE attribute.
+  if (!isVolatile_ && base->attrs().test(Attr::VOLATILE)) {
+    Warn(common::UsageWarning::NonVolatilePointerToVolatile,
+        "VOLATILE target associated with non-VOLATILE pointer"_warn_en_US);
+  }
+
+  if (msg) {
     return false;
   } else {
     context_.NoteDefinedSymbol(*base);

flang/lib/Support/Fortran-features.cpp

@@ -87,6 +87,7 @@ LanguageFeatureControl::LanguageFeatureControl() {
   warnUsage_.set(UsageWarning::NullActualForDefaultIntentAllocatable);
   warnUsage_.set(UsageWarning::UseAssociationIntoSameNameSubprogram);
   warnUsage_.set(UsageWarning::HostAssociatedIntentOutInSpecExpr);
+  warnUsage_.set(UsageWarning::NonVolatilePointerToVolatile);
   // New warnings, on by default
   warnLanguage_.set(LanguageFeature::SavedLocalInSpecExpr);
   warnLanguage_.set(LanguageFeature::NullActualForAllocatable);

flang/test/Semantics/assign02.f90

@@ -9,6 +9,9 @@ module m1
     sequence
     real :: t2Field
   end type
+  type t3
+    type(t2) :: t3Field
+  end type
 contains
 
   ! C852
@@ -80,6 +83,7 @@ subroutine s5
     real, pointer, volatile :: q
     p => x
     !ERROR: Pointer must be VOLATILE when target is a VOLATILE coarray
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
     p => y
     !ERROR: Pointer may not be VOLATILE when target is a non-VOLATILE coarray
     q => x
@@ -165,6 +169,36 @@ subroutine s11
     ca[1]%p => x
   end
 
+  subroutine s12
+    real, volatile, target :: x
+    real, pointer :: p
+    real, pointer, volatile :: q
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
+    p => x
+    q => x
+  end
+
+  subroutine s13
+    type(t3), target, volatile :: y = t3(t2(4.4))
+    real, pointer :: p1
+    type(t2), pointer :: p2
+    type(t3), pointer :: p3
+    real, pointer, volatile :: q1
+    type(t2), pointer, volatile :: q2
+    type(t3), pointer, volatile :: q3
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
+    p1 => y%t3Field%t2Field
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
+    p2 => y%t3Field
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
+    p3 => y
+    !OK:
+    q1 => y%t3Field%t2Field
+    !OK:
+    q2 => y%t3Field
+    !OK:
+    q3 => y
+  end
 end
 
 module m2

flang/test/Semantics/call03.f90

@@ -386,7 +386,9 @@ subroutine test16() ! C1540
     call contiguous(a) ! ok
     call pointer(a) ! ok
     call pointer(b) ! ok
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
     call pointer(c) ! ok
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
     call pointer(d) ! ok
     call valueassumedsize(a) ! ok
     call valueassumedsize(b) ! ok