llvm/lib/CodeGen/LiveRangeUtils.h:40: Iterators applied to wrong data structure ?

[dcb314]

Static analyser cppcheck says:

llvm/lib/CodeGen/LiveRangeUtils.h:40:6: error: Same iterator is used with different containers 'LR' and 'LR.segments'. [iterators1]

Source code is

typename LiveRangeT::iterator J = LR.begin(), E = LR.end();
// ...
LR.segments.erase(J, E);

So J and E are iterators for LR, but get used on LR.segments.

I am surprised this compiles.

[souvik150]

Hey can I pick this up? Im new to the project and just looking for some beginner friendly issues

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: None (dcb314)

Static analyser cppcheck says:

llvm/lib/CodeGen/LiveRangeUtils.h:40:6: error: Same iterator is used with different containers 'LR' and 'LR.segments'. [iterators1]

Source code is

typename LiveRangeT::iterator J = LR.begin(), E = LR.end();
// ...
LR.segments.erase(J, E);

So J and E are iterators for LR, but get used on LR.segments.

I am surprised this compiles.

[RKSimon]

@souvik150 this issue might be triage confirming the code is OK, or it might require a fix - good luck!

[arrowten]

@RKSimon Is this issue still open? I would like to work on it.

[RKSimon]

@RKSimon Is this issue still open? I would like to work on it.

It seems to be still there, so please triage it to see what needs doing - thanks!

[arrowten]

@RKSimon I doubt there is anything wrong with the source code. In the definition of LiveRange, it is clear that using iterator = Segments::iterator is the reason for using the code in the mentioned file. So either we can suppress the warning in cppcheck, but if there is anything, I am not sure if it needs to be done on llvm side.

[RKSimon]

CC @dcb314