bpo-42207: Make llvm profile data location reference absolute

[serge-sans-paille]

Otherwise, when running the testsuite, test_peg_generator tries to compile C
code using the optimized flags and fails because it cannot find the profile
data.

https://bugs.python.org/issue42207

[vstinner]

I would prefer to use $(abs_builddir): I am not sure that $PWD is portable on any shell.

Would you mind to add a comment referecing bpo-42207 to explain than an absolute path allows to run the test suite outside the build directory?

Is the problem that pegen uses "NODIST" variables like CFLAGS_NODIST and LDFLAGS_NODIST?

cc @stratakis @pablogsal @lysnikolaou

[pablogsal]

I would even prefer to deactivate this test on pgo builds or if detects that is running under a profile generation run given that it adds nothing useful and it takes a considerable time to execute.

[vstinner]

test_peg_generator is not part of the default profile task (./python -m test --pgo: test_peg_generator is not part of Lib/test/libregrtest/pgo.py). The problem is once Python it built, running test_peg_generator outside the build directory fails, according to https://bugs.python.org/issue42207

[pablogsal]

I know, what I am proposing is to skip it if it ever runs under a profile generation step

[serge-sans-paille]

Two possible approaches: https://sergesanspaille.fedorapeople.org/0001-Disable-peg-generator-test-under-PGO.patch and https://sergesanspaille.fedorapeople.org/0001-Fix-peg-parser-in-presence-of-profile-data.patch , which one do you prefer?

[pablogsal]

I assume that the first approach will be without the "Monkey patch CFLAGS" part, no?

In that case, I think I prefer the first one, as this test is particularly heavy with absolutely no gain on profile-based builds, it will benefit folks running the full test suite for PGO

[serge-sans-paille]

@pablogsal your assumption was correct. I picked that patch and updated the PR accordingly.

[pablogsal]

(Not submitting against master because it's not needed for master)

How so? The master branch has exactly the same test and the same way of generating profile data.

[serge-sans-paille]

(Not submitting against master because it's not needed for master)

How so? The master branch has exactly the same test and the same way of generating profile data.

oh, for some reasons these files were deleted on my local setup. Retargeting that PR to the master branch then

[brettcannon]

@serge-sans-paille can you open a new PR? When you rebase it messes up GitHub and then a ton of people get added as reviewers.