Invoke pip using Python

[radarhere]

Over at https://github.com/python-pillow/Pillow, we use CIFuzz.

At 2022-01-19T23:18:02Z, our CI job passed - https://github.com/python-pillow/Pillow/runs/4875290907 At 2022-01-20T10:29:08Z, our CI job failed - https://github.com/python-pillow/Pillow/runs/4880666670

2022-01-20T10:42:29.4244546Z   File "post-processing/fuzz_utils.py", line 17, in <module>
2022-01-20T10:42:29.4244876Z ModuleNotFoundError: No module named 'cxxfilt'

Taking a look at https://github.com/google/oss-fuzz/blob/23203939fc3032777f4440ccfeb4c8e19e7891d0/infra/base-images/base-builder/compile#L206-L216

I'm wondering if the required modules are being installed in a different copy of Python than what is later used. Since the base-builder-python installs Python, this doesn't seem impossible.

https://github.com/google/oss-fuzz/blob/23203939fc3032777f4440ccfeb4c8e19e7891d0/infra/base-images/base-builder-python/Dockerfile#L19

So this PR suggests installing the Python modules through python3 -m pip rather than pip3. I don't guarantee that it will fix the problem I mentioned, but you might agree that it is a good practice regardless.

[radarhere]

Someone else's thoughts on why python3 -m pip is better than pip3 - https://stackoverflow.com/questions/41307101/difference-between-pip3-and-python3-m-pip/67084664#67084664

[jonathanmetzman]

Sorry I thought I fixed this issue with https://github.com/google/oss-fuzz/pull/7199

I can consider your patch, but there is another underlying problem that I will try to fix first.

[jonathanmetzman]

By the way, is it intentional that CIFuzz only runs on your C/C++ PRs? https://github.com/python-pillow/Pillow/blob/main/.github/workflows/cifuzz.yml#L6

[jonathanmetzman]

Sorry I thought I fixed this issue with #7199

I think I did fix this in #7199 Can you trigger CIFuzz again please?

[radarhere]

Thanks, yes, it passes now. And yes, we're deliberately only running CIFuzz for C changes.

If you would like to merge this in just for the sake of python3 -m pip vs pip3, you can, but I'm also happy for this to be closed.

[jonathanmetzman]

/gcbrun trial_build.py python c c++ --engine libfuzzer --sanitizer coverage address

[maflcko]

Needs the merge conflicts solved, if still relevant.