libcurl.dll memory leak

[southernedge]

I did this

Hello, I would like to contact the developers.
I noticed a memory leak in libcurl.dll (libcurl-x64.dll) a long time ago. This is version independent.
Here is a small MS Visual Studio C test project showing this problem.
Downloading a file occurs in an endless loop. To speed up the manifestation of memory leaks, the download occurs in 64 threads.
Leave the program running for 15-30 minutes and you will see how memory consumption will increase many times over.
If there is my error and I do not release curl resources in a timely manner, then please suggest a solution to this problem.
Thank you very much for your work, attention and time spent!

I expected the following

No response

curl/libcurl version

8.4.0

operating system

Windows any

[bagder]

Please provide a stand-alone source code file that reproduces the problem, ideally without Windows specific code so that we can try it elsewhere.

You say it leaks in any libcurl version and I find it hard to believe that you tried most of them. Which versions did you use?

[southernedge]

For this test I used 8.4.0
The test code itself is _TestCurlLeakMem.cpp module.

[bagder]

If you cannot make a smaller and less Windows-centric recipe (I don't use Windows), then perhaps you can instead give us much more details about this claimed leak. What memory is leaking? Where is it allocated? How much?

(We test for memory leaks extensively, in all versions and all commits all the time.)

[gvanem]

You do not seems to call CInet::curl_global_cleanup() anywhere and LoadDll() loads multiple libcurls.
And this:

CInet::~CInet( void )
{
}

should at least call FreeLibrary().

[southernedge]

If you cannot make a smaller and less Windows-centric recipe (I don't use Windows), then perhaps you can instead give us much more details about this claimed leak. What memory is leaking? Where is it allocated? How much?

(We test for memory leaks extensively, in all versions and all commits all the time.)

I cannot give you an exact answer to your questions. Memory is leaking inside the dll module. The Visual Studio debugger does not show memory leaks inside external dll modules.
I see the memory increase after each file download using Windows Task Manager. The memory grows with each file download and does not return to its begin state.
The test program does not allocate memory at all. It's running idle.
It would be good if you took a quick look at the text of the module to see if there is an error on my part.

The memory leak problem is not noticeable if the command line curl.exe version is running - file downloaded and curl.exe exits.
But, if a dll library is used in an application for multiple downloads, when tens or hundreds of files can be downloaded in a cycle, then the memory leak becomes very noticeable.

[southernedge]

You do not seems to call CInet::curl_global_cleanup() anywhere and LoadDll() loads multiple libcurls.

• libcurl.dll is loaded once at the start of the program.
• In Windows, you can load a dll library any number of times, but physically it will be loaded once.
• As a rule, Windows does not unload the dll library from memory after FreeLibrary, so this function is of little use.

[bagder]

It would be good if you took a quick look at the text of the module to see if there is an error on my part.

It's not an easily read program. I did not spot a problem.

[southernedge]

It would be good if you took a quick look at the text of the module to see if there is an error on my part.

It's not an easily read program. I did not spot a problem.

Step by step it looks like this:

• get the file length
• divide it by the number of threads (64 thread)
• launch 64 threads.
• each thread will read one piece of the file
• expect all threads to be completed
• endless cycle

[southernedge]

static size_t WriteCallback( void *contents, size_t size, size_t nmemb, void *userp )
{
	WriteCallback_param *pParam = (WriteCallback_param*)userp;
	if ( pParam == NULL ) return 0;
	pParam->m_read += size * nmemb;
	if ( pParam->m_szMaxData > 0 && pParam->m_szMaxData < pParam->m_read ) return 0;
	return size * nmemb;
}

This callback function does not save anything inside the program, but there is a gradual increase in the memory.

[southernedge]

Dear Windows users,
could you test this program and confirm or deny the memory leak?

[bagder]

This callback function does not save anything inside the program, but there is a gradual increase in the memory.

If so, then if you just edit the simple.c example and add your callback in that in a single transfer in a single thread, that also leaks memory?

[southernedge]

If so, then if you just edit the simple.c example and add your callback in that in a single transfer in a single thread, that also leaks memory?
Ok, I will do some more testing with your example. However, this will take some time because downloading with one thread slowly leaked memory.
I will report you the results of the test.
Thank you!