Remove tests for warnings for test of UB that are NOT correct with LLVM. #3038
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See ziglang#2 at the end: http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_21.html These generally just return undefined value, but sometimes that undefined value is just certain bits, and Zig isn't prepared to do such analysis. The tests on / and % are correct however, because undefined can be 0, and division or remainder on 0 can cause a SIGFPE (as can INT_MAX / or % -1) There are more sophisticated cases where the result IS defined, but not warning on those is much more difficult, this does not actually remove even the easier to remove bogus warnings. There is a special case here that is also important, in that undef ^ undef => undef, NOT 0.
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This looks like an attempt to solve #1947 but it doesn't actually change the behavior, just the tests. More useful than this PR would be adding a comment to #1947 noting all the differences (so that we have a checklist). The implementation of #1947 will remove these tests and add additional tests which exercise the undefined values at comptime and runtime and make sure behavior is correct. That issue is probably not very contributor friendly - if you tackle it I recommend one operation at a time, at least for the first few PRs. |
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See #2 at the end:
http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_21.html
These generally just return undefined value, but sometimes that undefined
value is just certain bits, and Zig isn't prepared to do such analysis.
The tests on / and % are correct however, because undefined can be 0,
and division or remainder on 0 can cause a SIGFPE (as can INT_MAX / or % -1)
There are more sophisticated cases where the result IS defined,
but not warning on those is much more difficult, this does not actually remove
even the easier to remove bogus warnings.
There is a special case here that is also important, in that undef ^ undef => undef,
NOT 0.