[flang-commits] [flang] f546b6e - [Flang] Relaxing an error when contiguous pointer is assigned to a non-contig… (#86781)

[via flang-commits]

Author: harishch4
Date: 2024-04-01T17:13:22+05:30
New Revision: f546b6ef3c15a156959dde16fa5f03a350a0a2be

URL: https://github.com/llvm/llvm-project/commit/f546b6ef3c15a156959dde16fa5f03a350a0a2be
DIFF: https://github.com/llvm/llvm-project/commit/f546b6ef3c15a156959dde16fa5f03a350a0a2be.diff

LOG: [Flang] Relaxing an error when contiguous pointer is assigned to a non-contig… (#86781)

…uous function.

Fix from [thtsikas](https://github.com/thtsikas) based on a discussion
in
[slack](https://flang-compiler.slack.com/archives/C5C58TT32/p1711124374836079).

Example:
```
Program test
  Integer, Pointer, Contiguous :: cont(:)
  Interface
     Function f()
       Integer, Pointer :: f(:)
     End Function
  End Interface
  cont => f()
  Print *, cont(3)
End Program

Function f()
  Integer, Pointer :: f(:)
  Allocate (f(4),Source=[1,1,42,1])
  ! f => f(4:1:-1)        !! not contiguous, runtime error
End Function f
```

Understanding is that the standard intended to allow this pattern. The
restriction 10.2.2.3 p6 Data pointer assignment "If the pointer object
has the CONTIGUOUS attribute, the pointer target shall be contiguous."
is not associated with a numbered constraint. If there is a mechanism
for injecting runtime checks, this would be a place to do it. Absent
that, a warning is the best we can do.

No other compiler treats contigPtr => func() as an error when func() is
not CONTIGUOUS, so a warning would probably be better for consistency.
https://godbolt.org/z/5cM6roeEE

Added: 
    

Modified: 
    flang/lib/Semantics/pointer-assignment.cpp

Removed: 
    


################################################################################
diff  --git a/flang/lib/Semantics/pointer-assignment.cpp b/flang/lib/Semantics/pointer-assignment.cpp
index 58155a29da1ee5..4b4ce153084d8e 100644
--- a/flang/lib/Semantics/pointer-assignment.cpp
+++ b/flang/lib/Semantics/pointer-assignment.cpp
@@ -266,7 +266,7 @@ bool PointerAssignmentChecker::Check(const evaluate::FunctionRef<T> &f) {
   } else if (isContiguous_ &&
       !funcResult->attrs.test(FunctionResult::Attr::Contiguous)) {
     msg = "CONTIGUOUS %s is associated with the result of reference to"
-          " function '%s' that is not contiguous"_err_en_US;
+          " function '%s' that is not known to be contiguous"_warn_en_US;
   } else if (lhsType_) {
     const auto *frTypeAndShape{funcResult->GetTypeAndShape()};
     CHECK(frTypeAndShape);