C++: Improve function pointer resolution #17788
Merged
Conversation
This file contains 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
jketema
reviewed
Oct 17, 2024
cpp/ql/lib/change-notes/2024-10-16-new-api-for-call-target-resolution.md
Outdated
Show resolved
Hide resolved
| * | ||
| * Note that `call` may be a call to a function pointer expression. | ||
| */ | ||
| Function getARuntimeTarget(Call call) { |
There was a problem hiding this comment.
I'm always slightly confused. Is DataFlowUtil the file whose contents users may still depend upon, although it's located in internal?
There was a problem hiding this comment.
Correct:
I don't know why this was done like this. This file structure is also present in the old AST dataflow, and we just copied it for IR dataflow.
We could actually change this, and maybe rename DataFlowUtil to DataFlowPublic to clear this confusion like it's been done for newer languages:
(although it looks like every language still stores the file in internal for some reason 🤔)
…olution.md Co-authored-by: Jeroen Ketema <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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 uses the existing "lambda resolution" mechanism in the dataflow library to resolve calls through function pointers.
We already track function addresses flowing into MaD models that specify a function pointer as an input (which was added in e9cd2dc). However, we never went the extra mile and added it when you call the function pointer in the source code.
This PR adds the one line which enables this. This should hopefully mean that we resolve a lot more function pointers.
Ideally, I would have liked to also remove the old function pointer resolution and virtual dispatch code, but since this is such a small change I think we should just get this improvement in now.
@bdrodes noted that he would also like for the call target resolution to be exposed as a predicate. I've snuck that into this PR in a99d576
All the results look like new genuine results with no performance problems in sight 🥳