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authorZack Weinberg <zackw@panix.com>2019-08-19 13:51:25 -0400
committerZack Weinberg <zackw@panix.com>2020-01-06 15:39:28 -0500
commitc246b06a68ca6ef1ffcde790980a47bcbbedece9 (patch)
tree811f93e2b914d28692a38753d4b7dd25dda37ebe /nis/Depend
parentd5f4d0ac6a14cc3385dc4180698f939ca0ee00f5 (diff)
downloadglibc-zack/obsolete-time-functions.tar.gz
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Warn when gettimeofday is called with non-null tzp argument. zack/obsolete-time-functions
Since there are no known uses of gettimeofday's vestigial "get time
zone" feature that are not bugs, add a fortify-style wrapper inline to
sys/time.h that issues a warning whenever gettimeofday is called with
a second argument that is not a compile-time null pointer
constant.

At present this is only possible with GCC; clang does not implement
attribute((warning)).  The wrapper is only activated when __OPTIMIZE__
is defined because it throws false positives when optimization is off,
even though it's an always-inline function.

An oversight in the implementation of __builtin_constant_p causes it
to fail to detect compile-time *pointer* constants unless they are
cast to an integer of a different size.  (Loss of data in this cast is
harmless; the overall expression is still constant if and only if the
original pointer was.)  This is GCC bug 95514.  Thanks to
Kamil Cukrowski <kamilcukrowski@gmail.com> for the workaround.
As a precaution, I added a static assertion to debug/warning-nop.c to
make sure that the cast _is_ casting to an integer of a different
size; this is too unlikely a scenario to be worth checking in the
public header, but if someone ever adds a port where short is the
same size as intptr_t, we'll still catch it.
Diffstat (limited to 'nis/Depend')
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