Date: Tue, 10 Feb 2004 15:12:40 -0500 From: Bill Moran <wmoran@potentialtech.com> To: freebsd-chat@freebsd.org Subject: Could use some help with variable length argument lists Message-ID: <40293B38.30401@potentialtech.com>
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I'm so frustrated I could cry.
I want my application to be able to do all kinds of logging, so I wrote a log
function:
void
_log(int level, const char *message, ...)
{
va_list ap;
char **format, **errmsg;
va_start(ap, message);
if (level <= LOGLEVEL) {
asprintf(format, "PID %d: %s", getpid(), message);
vasprintf(errmsg, *format, ap);
free(*format);
syslog(LOG_INFO | LOG_LOCAL1, *errmsg);
if (LOGLEVEL == 10)
printf(*errmsg);
free(*errmsg);
}
va_end(ap);
}
Doesn't seem too difficult, right? However, if I call the function
from elsewhere in my application like this:
_log(1, "Log test");
I get a coredump! gdb complains that message is "out of bounds"
on the line "asprintf(format, "PID %d: %s", getpid(), message);"
I'm at the end of my rope with this. I really need a way to easily
log with variable arguments or I'll never get some other issues with
this application debugged! If I tweak the _log function to this:
void
_log(int level, char *message)
{
if (level <= LOGLEVEL) {
syslog(LOG_INFO | LOG_LOCAL1, "PID %d: %s", getpid(), message);
if (LOGLEVEL == 10)
printf("PID %d: %s", getpid(), message);
}
}
everything works just dandy (I haven't changed any other code anywhere
else! I'm not _using_ variable arguments to _log() yet)
What is is between these two functions that causes the first one to
coredump, yet the second one works fine? I can only guess that my
usage of va_* isn't quite right, but how is that affecting the message
pointer?
--
Bill Moran
Potential Technologies
http://www.potentialtech.com
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