workflows: Run the address sanitizer (ASan) build during CI.

[jepler]

Summary

ASan, the address sanitizer can find interesting bugs using additional runtime checks. For instance, it detected the memory leak now fixed at https://github.com/micropython/berkeley-db-1.xx/pull/1 and possibly other interesting findings I've previously submitted.

This patch set enables ASan for the 64-bit unix coverage build.

Testing

Lots and lots of builds until it was green!

Trade-offs and Alternatives

I had to disable one entire class of check, "stack use after return". I wasn't able to find good information about how this mode works, but it clearly violates assumptions that micropython makes in nlr, gc, and stack space checking.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.56%. Comparing base (5ade8b7) to head (264ed6c). Report is 29 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #17503   +/-   ##
=======================================
  Coverage   98.56%   98.56%           
=======================================
  Files         169      169           
  Lines       21948    21948           
=======================================
  Hits        21632    21632           
  Misses        316      316           

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[github-actions[bot]]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO_W
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32

[jepler]

aha https://github.com/google/sanitizers/wiki/AddressSanitizerUseAfterReturn explains how it works. I'm not sure how you'd make this mode work with all micropython's stack trickery, there was a link to research on how to make it interoperate with some other kind of gc but it's dead and not archived that I could find.

[jepler]

ah, found it in their git history: llvm introduced two functions to allow gc to work with the stack use sanitizer. I don't know if gcc did likewise, and I'm not sure how exactly they'd be used in practice.

[jepler]

Here's a program that seems to know how to gather pointers in the fake stack for gc: https://github.com/karolba/serenity/blob/2a563b9de65886c0a5644b8ea41bef14e5587735/Userland/Libraries/LibJS/Heap/Heap.cpp#L163

[jepler]

(just to be clear: I don't think this PR should be held for want of being able to use that specific sanitizer.)

[dpgeorge]

Rebased and merged in 9a5cf0e3dbb7dbc1b66ef67dd2fec0245d24e37e through 1eb27e11f3bf8e5e0ee13191ef1e9c30b00f9ead