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| author | Zack Weinberg <zackw@panix.com> | 2019-08-19 13:51:25 -0400 |
|---|---|---|
| committer | Zack Weinberg <zackw@panix.com> | 2020-01-06 15:39:28 -0500 |
| commit | c246b06a68ca6ef1ffcde790980a47bcbbedece9 (patch) | |
| tree | 811f93e2b914d28692a38753d4b7dd25dda37ebe /debug/warning-nop.c | |
| parent | d5f4d0ac6a14cc3385dc4180698f939ca0ee00f5 (diff) | |
| download | glibc-zack/obsolete-time-functions.tar glibc-zack/obsolete-time-functions.tar.gz glibc-zack/obsolete-time-functions.tar.bz2 glibc-zack/obsolete-time-functions.zip | |
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 'debug/warning-nop.c')
| -rw-r--r-- | debug/warning-nop.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/debug/warning-nop.c b/debug/warning-nop.c index 4ab7e182b7..9bd890a20b 100644 --- a/debug/warning-nop.c +++ b/debug/warning-nop.c @@ -67,4 +67,13 @@ nop (void) #define __builtin___strncpy_chk(dest, src, len, bos) NULL #define __builtin_object_size(bos, level) 0 +/* The code in sys/time.h that uses __warndecl has to work around GCC + bug 91554. The work-around is only effective if intptr_t is not + the same size as short. */ +#include <stdint.h> +_Static_assert (sizeof (intptr_t) != sizeof (short), + "workaround for GCC bug 91554 in sys/time.h" + " is only effective when short is smaller than a pointer"); + #include <string.h> +#include <sys/time.h> |