Ensure header CRC is written as unsigned int

[bridadan]

Description

Fixes #9750. The bootloader merge would fail since the CRC produces an unsigned 32 bit integer, however we specified it as a signed 32 bit integer.

I've tested this on a K64F and ran an update over Pelion, seems to work ok!

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

Reviewers

@theotherjimmy - tools team review

Release Notes

[cmonr]

@bridadan We've done this fix before (#8788), only to have it reverted (#8915)

Thoughts?

[bridadan]

Hey @cmonr, thanks for linking that, I thought this changeset looked familiar 😆

This is the error that appeared in the linked PRs that concerned me: #8788 (comment)

Traceback (most recent call last):
  File "/builds/ws/mbed-os-ci_cloud-client-test/mbed-cloud-client-example/mbed-os/tools/make.py", line 71, in wrapped_build_project
    src_dir, build_dir, mcu, *args, **kwargs
  File "/builds/ws/mbed-os-ci_cloud-client-test/mbed-cloud-client-example/mbed-os/tools/build_api.py", line 549, in build_project
    merge_region_list(region_list, res, notify)
  File "/builds/ws/mbed-os-ci_cloud-client-test/mbed-cloud-client-example/mbed-os/tools/build_api.py", line 422, in merge_region_list
    _fill_header(region_list, region).tofile(header_filename, format='hex')
  File "/builds/ws/mbed-os-ci_cloud-client-test/mbed-cloud-client-example/mbed-os/tools/build_api.py", line 392, in _fill_header
    header.puts(start, struct.pack(fmt, zlib.crc32(ih.tobinarray())))
error: integer out of range for 'L' format code

I've just pushed a change that I believe will solve this issue. I've followed the note in the python docs: https://docs.python.org/2.7/library/zlib.html#zlib.crc32

To generate the same numeric value across all Python versions and platforms use crc32(data) & 0xffffffff. If you are only using the checksum in packed binary format this is not necessary as the return value is the correct 32bit binary representation regardless of sign.

[cmonr]

@ARMmbed/mbed-os-maintainers @JanneKiiskila #9783 (comment) Thoughts?

@bridadan Yeah, I'm just being cautious. I thought that this would be the right fix as well, and still thing so, but don't want us to get into a bad state again.

[0xc0170]

Lets run CI !

[0xc0170]

Set to 5.12 to sit on master and run additional nightly tests

[bridadan]

Hey @cmonr, I'm pretty sure the last commit I pushed should avoid the error: integer out of range for 'L' format code problem. I confirmed the cases that cause that error and also confirmed that bitwise "anding" the values with 0xffffffff forces them to the right size:

import struct
>>> fmt = "<L"
>>> val = 0xffffffff + 1
>>> struct.pack(fmt, val)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
struct.error: integer out of range for 'L' format code
>>> struct.pack(fmt, val & 0xffffffff)
'\x00\x00\x00\x00'
>>> val = -1
>>> struct.pack(fmt, val)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
struct.error: integer out of range for 'L' format code
>>> struct.pack(fmt, val & 0xffffffff)
'\xff\xff\xff\xff'

[cmonr]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 12 of 12 test jobs passed
Build number : 1
Build artifacts