Re: libcurl 8.0.1 and mem leaks reported on callback - windows x64 build

From: Henrik Holst via curl-library <curl-library_at_lists.haxx.se>
Date: Sun, 9 Apr 2023 00:03:47 +0200

sounds like the VS2022 CRT debug tools don't unwind the stack before the
check so it doesn't call the std:string destructor or something like that.
I compiled your code on Linux and run it using Valgrind which is the #1
when it comes to memleak detection and it found none:

henrik_at_Sineya:~$ valgrind ./memleaktest
==62452== Memcheck, a memory error detector
==62452== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==62452== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==62452== Command: ./hej
==62452==

The response code is: 200
the curl return code is: 0
==62452==
==62452== HEAP SUMMARY:
==62452== in use at exit: 0 bytes in 0 blocks
==62452== total heap usage: 4,633 allocs, 4,633 frees, 444,149 bytes
allocated
==62452==
==62452== All heap blocks were freed -- no leaks are possible
==62452==
==62452== For lists of detected and suppressed errors, rerun with: -s
==62452== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

/HH

Den lör 8 apr. 2023 kl 19:11 skrev Tyler Wilson via curl-library <
curl-library_at_lists.haxx.se>:

> Hi everyone,
>
> I'm still learning, but I'm hoping you can help.
>
> I have libcurl up and running and love it. But, I'm seeing memory leaks
> and not sure if it's me or something else.
>
> Stats:
> - Windows platform x64, with Visual Studio 2022.
> - Downloaded source code from curl website as a .gz file.
> - Building according to win instructions using Native Tools:
>
> 1. *nmake /f Makefile.vc mode=dll MACHINE=x64 WITH_SSL=no DEBUG=no*
>
>
> I have a very simple program that sends data to Mockbin. It responds with
> the payload I sent plus a whole lot more.
>
> When my program is done though, VS2022 CRT debug tools claim that there is
> a memory leak. Looking at the debug output, it's coming from the response
> that I'm getting from Mockbin.
>
> 'curlmemleakexample.exe' (Win32): Unloaded
> 'C:\Windows\System32\FWPUCLNT.DLL'
> Detected memory leaks!
> Dumping objects ->
> {160} normal block at 0x000002181100D260, 2496 bytes long.
> Data: < { > 00 20 20 20 20 20 20 20 20 7B 0A 20 20 20 20 20
> {159} normal block at 0x00000218110062C0, 16 bytes long.
> Data: <_at_d > 40 64 80 A5 F6 7F 00 00 00 00 00 00 00 00 00 00
> Object dump complete.
>
> The data above is the response from Mockbin based on the length of the
> bytes and what I saw come back from Wireshark over HTTP. I am calling
> global_init before my program starts, and calling global_free when I'm
> done. I have pasted my sample of code at the following link:
>
>
> https://www.codebin.cc/code/304ead33e4dd78b7bb1eeb36460eed6a9a4fe85506b6f4185329a6e861e00f6e
>
> Why would I still be getting reported memory leaks on the information from
> the callback? Is it because my callback is a global function? Am I maybe
> not understanding something about the API and maybe it requires the
> function to do something different?
>
> Many thanks in advance for your help and assistance. I hope I was able to
> give you enough details.
>
> Thanks....Tyler!
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Received on 2023-04-09