Fix LWG Issue 4060 (fix submdspan to prevent invalid pointer creation) #323
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LWG Issue 4060 ("submdspan preconditions do not forbid creating
invalid pointer") currently fails, because submdspan does not
correctly handle the case where first_ of one or more slices is out of
bounds.
This commit adds two tests taken straight from the Issue.
As expected, one test passes and the other test fails.
However, both tests trigger undefined behavior
for the layout mapping.
... in favor of macros. In theory, this would help us backport submdspan to C++14.
dalg24
reviewed
Apr 4, 2024
...thus following the pattern of other uses of assert in the same header file.
* Add MDSPAN_INLINE_FUNCTION to bounds-checking functions * Pass indices by value to bounds-checking functions * Don't use std::forward for slices (use const ref instead) * Use required_span_size() in test
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dalg24
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Apr 4, 2024
dalg24
approved these changes
Apr 4, 2024
Co-authored-by: Damien L-G <dalg24+github@gmail.com>
crtrott
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Link to issue: https://cplusplus.github.io/LWG/issue4060
I aimed for C++14 backwards compatibility. Item (2) above is not strictly necessary to fix the issue, but it does help with finding the issue in the first place.
Bounds checking is only enabled in a debug build (if
NDEBUGis not defined). It involves some fold expressions overassertexpressions. I'm not attached to the use ofassertfor reporting errors.