kernel: fix GAP_STATIC_ASSERT fallback code #2691
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If `_Static_assert` resp. `static_assert` are not available, we fall back to a trick involving a typedef that's invalid if the assertion fails. In order to avoid clashes with repeating (identical) typedefs, we tried to insert the line number (via the `__LINE__` macro), but that did not actually work due to the way the C preprocessor works. To fix this, we need to use two helper macros which ensure `__LINE__` get evaluated before being concatenated to another string.
fingolfin
added
kind: bug
Codecov Report
@@ Coverage Diff @@
## master #2691 +/- ##
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+ Coverage 75.42% 75.42% +<.01%
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Files 478 478
Lines 241598 241598
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+ Hits 182227 182228 +1
+ Misses 59371 59370 -1
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ChrisJefferson
approved these changes
Aug 10, 2018
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Good fix. I should have spotted this originally, as I've had exactly this kind of stupid preprocessor issue before. |
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@ChrisJefferson we are getting further reports about this problem and advise to apply the patch to GAP 4.9.2. Should this be backported into stable-4.9 branch then? |
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If there is going to be a 4.9.3 release, then we should definitely backport this. |
olexandr-konovalov
added
backport-to-4.9-DONE
release notes: added
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Backported and added to release notes. |
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If
_Static_assertresp.static_assertare not available, we fall back to atrick involving a typedef that's invalid if the assertion fails.
In order to avoid clashes with repeating (identical) typedefs, we tried to
insert the line number (via the
__LINE__macro), but that did not actuallywork due to the way the C preprocessor works. To fix this, we need to use two
helper macros which ensure
__LINE__get evaluated before being concatenatedto another string.
I am not sure whether it's worth to mention this in the release notes; but then we did get a report involving this problem, so perhaps it is... In any case, I've not yet added any "release notes" labels.