[issue30124] Fix C aliasing issue in Python/dtoa.c to use strict aliasing on Clang 4.0

[STINNER Victor]

STINNER Victor added the comment:

dtoa.c is now compiled with -fno-string-aliasing (for any clang version, not only clang 4.0) on Python 3.5, 3.6 and 3.7.

It was decided to not touch dtoa.c to not diverge from upstream.

Thanks Dimitry Andric and Mark Dickinson for your reviews and support in this cryptic issue!

Note 1: We consider that Clang 4.0 is wrong, whereas GCC respects the C99 standard for aliasing on unions. But I don't think that it matters much who is wrong or not :-)

Note 2: Python 2.7 already used -fno-strict-aliasing on all .c files because of its design of PyObject structures, fixed in Python 3.

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resolution:  -> fixed
stage:  -> resolved
status: open -> closed

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<http://bugs.python.org/issue30124>
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