Jeff Johnson wrote:
I happen to have a valgrind trace on my screen that shows the issue
==25160==
==25160== 49 bytes in 1 blocks are still reachable in loss record 2 of 2
==25160== at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==25160== by 0x314D9A: poptGetNextOpt (popt.c:1203)
==25160== by 0x40697CD: rpmcliInit (poptALL.c:751)
==25160== by 0x804AC45: main (rpmqv.c:385)
==25160==
The "memory leak" is actually a POPT design feature. Every string
returned from POPT is malloc'd so that an application
can do whatever it wishes with the string without
worrying about side effects of fiddling with the memory.
Unfortunately, POPT is mostly not used correctly, and the expectation is
Hey POPT handles argv strings, I shouldn't _HAVE_ to manage those!?!
I don't mind having to manage those, as long as it is documented.
I just started using libpopt for the very first time today and checked
my code with valgrind which showed a leak. The minimal program below
always leaks an amount of memory equal to the length of the argument of
the "hostname" option +1. Despite the fact that I think I'm free-ing
everything I'm supposed to free... After skimming the libpopt source I
inserted the two commented lines that, when uncommented (duh), seem to
fix the leak... lucky shot I guess. :)
Does this not demonstrate that there actually is a memory leak in popt?
If not, I would appreciate someone explaining how I'm using libpopt wrongly.
#include <stdio.h>
#include <stdlib.h>
#include <popt.h>
/** #include "/tmp/popt-1.14/poptint.h" **/
struct opts {
char *hostname;
int verbose;
} opts;
struct poptOption optTable[] = {
{"hostname", 'h', POPT_ARG_STRING, &opts.hostname,
0, "hostname", "HOST" },
{"verbose", 'v', POPT_ARG_NONE, &opts.verbose,
0, "be verbose", 0 },
POPT_AUTOHELP
POPT_TABLEEND
};
int main( int argc, const char **argv )
{
poptContext optCon;
optCon = poptGetContext(NULL, argc, argv,
optTable, POPT_CONTEXT_POSIXMEHARDER);
poptGetNextOpt(optCon);
printf("Options:\n"
"hostname: %s\n"
"verbose: %d\n",
opts.hostname,
opts.verbose);
free(opts.hostname);
/** free(optCon->os->nextArg); **/
poptFreeContext(optCon);
return 0;
}
Regards,
Mark.
I get a tedious bug report every couple of months from otherwise honest
attempts to use valgrind for application "squeaky clean" memory auditing.
Should this behavior be changed in POPT 2.0? It's a 1-liner change to remove
a strdup() somewhere, but the change does have profound (but minor, who
actually cares about a 49b 1-time memory leak these days) ramifications.
Meanwhile I'm way tired of explaining why its _NOT_ a memory leak, but rather
buggy use of POPT.
Opinions welcomed.
73 de Jeff
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