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warnx: Save errno across calls that might change it.

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When warn() family of functions is being used after err_set_file() has
been set to, for example, /dev/null, errno is being clobbered,
rendering it unreliable after, for example, procstat_getpathname()
when it is supposed to emit a warning. Then the errno is changed to
Inappropriate ioctl for device, destroying the original value (via
calls to fprintf()functions).

Submitted by: Juraj Lutter
Differential Revision: https://reviews.freebsd.org/D26871
This commit is contained in:
Warner Losh 2020-10-23 23:56:00 +00:00
parent 3e7449a37b
commit 4e0771b2da
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=366982
1 changed files with 8 additions and 0 deletions
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8
lib/libc/gen/err.c
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@ -161,6 +161,9 @@ warnc(int code, const char *fmt, ...)
void
vwarnc(int code, const char *fmt, va_list ap)
{
static int saved_errno;
saved_errno = errno;
if (err_file == NULL)
err_set_file(NULL);
fprintf(err_file, "%s: ", _getprogname());
@ -169,6 +172,7 @@ vwarnc(int code, const char *fmt, va_list ap)
fprintf(err_file, ": ");
}
fprintf(err_file, "%s\n", strerror(code));
errno = saved_errno;
}
void
@ -183,10 +187,14 @@ warnx(const char *fmt, ...)
void
vwarnx(const char *fmt, va_list ap)
{
static int saved_errno;
saved_errno = errno;
if (err_file == NULL)
err_set_file(NULL);
fprintf(err_file, "%s: ", _getprogname());
if (fmt != NULL)
vfprintf(err_file, fmt, ap);
fprintf(err_file, "\n");
errno = saved_errno;
}