After adding the final touches to my program, I ran valgrind to check for memory leaks. And to my surprise, I read that chunks of memory were used and never deallocated, although I made sure I freed every resource I was using before ending the program. 和永远不会释放,但我确信我释放我结束程序之前,利用一切资源。 Looking closely at the report, I find that almost all of the report said the leaks were coming from libcurl function calls. Here's a sample from the report:
==3555== HEAP SUMMARY:
==3555== in use at exit: 179,937 bytes in 4,212 blocks
==3555== total heap usage: 18,080 allocs, 13,868 frees, 10,050,116 bytes allocated
==3555==
==3555== Searching for pointers to 4,212 not-freed blocks
==3555== Checked 486,368 bytes
==3555==
==3555== 2 bytes in 2 blocks are still reachable in loss record 1 of 667
==3555== at 0x4C29F90: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3555== by 0x542C9C9: strdup (in /usr/lib/libc-2.20.so)
==3555== by 0x4E58C1E: ??? (in /usr/lib/libcurl.so.4.3.0)
==3555== by 0x4E6A90F: ??? (in /usr/lib/libcurl.so.4.3.0)
==3555== by 0x4E6B4A0: curl_multi_perform (in /usr/lib/libcurl.so.4.3.0)
==3555== by 0x404141: url_fopen (network.c:226)
==3555== by 0x403737: load_tracks (PlayMusic.c:718)
==3555== by 0x401E1C: main (PlayMusic.c:145)
==3555==
==3555== 2 bytes in 2 blocks are still reachable in loss record 2 of 667
==3555== at 0x4C29F90: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3555== by 0x542C9C9: strdup (in /usr/lib/libc-2.20.so)
==3555== by 0x4E58C3A: ??? (in /usr/lib/libcurl.so.4.3.0)
==3555== by 0x4E6A90F: ??? (in /usr/lib/libcurl.so.4.3.0)
==3555== by 0x4E6B4A0: curl_multi_perform (in /usr/lib/libcurl.so.4.3.0)
==3555== by 0x404141: url_fopen (network.c:226)
==3555== by 0x403737: load_tracks (PlayMusic.c:718)
==3555== by 0x401E1C: main (PlayMusic.c:145)
Here is the url_fopen
function that valgrind complains about:
URL_FILE *url_fopen(const char *url, const char *operation)
{
/*
this code could check for URLs or types in the 'url' and
basicly use the real fopen() for standard files
*/
URL_FILE *file;
file = malloc(sizeof(URL_FILE));
if (!file)
return NULL;
memset(file, 0, sizeof(URL_FILE));
if ((file->handle.file = fopen(url, operation)))
file->type = CFTYPE_FILE; /* marked as URL */
else {
file->type = CFTYPE_URL; /* marked as URL */
file->handle.curl = curl_easy_init();
curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA,
file);
curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE,
0L);
curl_easy_setopt(file->handle.curl,
CURLOPT_WRITEFUNCTION,
write_callback);
if (!multi_handle)
multi_handle = curl_multi_init();
curl_multi_add_handle(multi_handle,
file->handle.curl);
/*
lets start the fetch
*/
curl_multi_perform(multi_handle,
&file->still_running);
if ((file->buffer_pos == 0) && (!file->still_running)) {
/*
if still_running is 0 now, we should return NULL
*/
/*
make sure the easy handle is not in the multi handle anymore
*/
curl_multi_remove_handle(multi_handle,
file->handle.curl);
/*
cleanup
*/
curl_easy_cleanup(file->handle.curl);
curl_multi_cleanup(multi_handle);
fclose
free(file);
file = NULL;
}
}
return file;
}
Are these just false positives ? If they are, how can I force valgrind to ignore them. If they are not, is there a solution to this leaking problem ?
Try using curl_global_init(CURL_GLOBAL_DEFAULT);
at the start of the program. This sets the environment that libcURL
requires.
It is recommended that, this function must be called at least once within a program. Also it is not thread-safe so it must be called at the very beginning of the program, before any threads start.
Also you should call curl_global_cleanup();
once for each call to curl_global_init()
, at the end of the program when you are done using libcURL
. This will clean up all things used by libcURL
.
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