[Flang-rt] Implement same behavior as -O3 for zero-length arrays #171480
+1
−1
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This PR addresses an issue of incorrect code where an unallocated array is passed to a routine as a zero-length array. When compiling such a code with -O3, the assignment is ignored, but -O0 chokes in flang-rt due to the above condition in the original code. Adding the extra condition makes the behavior consistent with -O3.
mjklemm
requested review from
Copilot,
kiranchandramohan,
klausler,
kparzysz and
tblah
Contributor
There was a problem hiding this comment.
Pull request overview
This PR fixes a runtime crash in flang-rt when handling unallocated arrays passed as zero-length arrays. The change ensures that -O0 behavior matches -O3 by allowing assignments to unallocated zero-length arrays without triggering a runtime error.
Key Changes:
- Modified the runtime check in
assign.cppto skip the crash condition when an unallocated array has zero elements
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
mjklemm
changed the title
klausler
approved these changes
Dec 9, 2025
Contributor
klausler
left a comment
klausler
left a comment
There was a problem hiding this comment.
Approved, and please ignore Copilot's request to make the error message confusing.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This PR addresses an issue of incorrect code where an unallocated array is passed to a routine as a zero-length array. When compiling such a code with -O3, the assignment is ignored, but -O0 chokes in flang-rt due to an allocation check condition in the original code. Adding the extra condition makes the behavior consistent with -O3.