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Aptrug

Member

Registered: 2021-09-11

Posts: 1

[SOLVED] Memory leaks in my C program when calling alpm_list_msort()

Without alpm_list_msort():
    Locally installed packages are printed from A-Z.
   

valgrind a.out

and

gcc -lalpm -g -fsanitize=leak,address,undefined ./listpkgs.c; ./a.out

show that no there are no leaks.

With alpm_list_msort() (change SORT_PKG_LIST macro constant from 0 to 1):
    Locally installed packages are printed based on their installation size (from smallest to biggest).
   

valgrind a.out

and

gcc -lalpm -g -fsanitize=leak,address,undefined ./listpkgs.c; ./a.out

show that there are some leaks.

/* Compile with "gcc -g -lalpm listpkgs.c" */
#include <alpm.h>
#include <assert.h>
#include <stdio.h>

#define SORT_PKG_LIST 0

static void
print_pkg(alpm_pkg_t *pkg)
{
	printf("%s: %ld\n", alpm_pkg_get_name(pkg), alpm_pkg_get_isize(pkg));
}

static void
iterate_over_pkg_list(alpm_list_t *pkg_list)
{
	while (pkg_list != NULL) {
		print_pkg((alpm_pkg_t *)pkg_list->data);
		pkg_list = alpm_list_next(pkg_list);
	}
}

#if SORT_PKG_LIST
static int
isize_comp(const void *pkg1, const void *pkg2)
{
	return alpm_pkg_get_isize((alpm_pkg_t *)pkg1) >
	       alpm_pkg_get_isize((alpm_pkg_t *)pkg2);
}

static alpm_list_t *
get_sorted_pkg_list(alpm_db_t *db)
{
	alpm_list_t *unsorted_pkg_list;
	alpm_list_t *sorted_pkg_list;

	unsorted_pkg_list = alpm_db_get_pkgcache(db);
	assert(unsorted_pkg_list != NULL);

	sorted_pkg_list = alpm_list_msort(
	    unsorted_pkg_list, alpm_list_count(unsorted_pkg_list), isize_comp);

	return sorted_pkg_list;
}
#endif

int
main()
{
	int retval;
	alpm_handle_t *handle;
	alpm_db_t *db;
	alpm_list_t *pkg_list;

	handle = alpm_initialize("/", "/var/lib/pacman/", NULL);
	assert(handle != NULL);

	db = alpm_get_localdb(handle);

#if SORT_PKG_LIST
	pkg_list = get_sorted_pkg_list(db);
#else
	pkg_list = alpm_db_get_pkgcache(db);
	assert(pkg_list != NULL);
#endif
	iterate_over_pkg_list(pkg_list);

	retval = alpm_release(handle);
	assert(retval == 0);
}

I've taken a look at libalpm_list(3) and the man page does not mention anything about freeing memory after calling alpm_list_msort().
Any help please?

Last edited by Aptrug (2022-03-26 14:05:22)

Allan

Pacman

From: Brisbane, AU

Registered: 2007-06-09

Posts: 11,497

Website

Re: [SOLVED] Memory leaks in my C program when calling alpm_list_msort()

It is late at night, so I have not looked too deeply, but I'm guessing that the pointer stored in db->pkgcache no longer points to the top of the list after the msort, so not all entries are freed in alpm_release().  Note the alpm_list_t essentially points at the first element - it is a very simple list...  Though not documented, it seems the list should not be altered.  Doing a copy and free fixes it

	db = alpm_get_localdb(handle);

	pkg_list = alpm_list_copy(alpm_db_get_pkgcache(db));
	assert(pkg_list != NULL);

	pkg_list = alpm_list_msort(
	    pkg_list, alpm_list_count(pkg_list), isize_comp);

	iterate_over_pkg_list(pkg_list);

	alpm_list_free(pkg_list);

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