[vlc-devel] [PATCH] libvlc: dump object types abd names when leaking
Rémi Denis-Courmont
remi at remlab.net
Thu Feb 21 13:02:42 CET 2019
Some people also refuse to support building with the Java compiler. VLC is a C/C++11 copyleft project. You can't build it with a C89, or Microsoft C dialect, or Java compiler, and you can't redistribute it if you have proprietary non-OS dependencies.
I don't know who some people are, but I am not aware of anybody preventing build with another C11/C++11 toolchain than GCC or Clang.
Le 21 février 2019 13:55:48 GMT+02:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>On 21/02/2019 12:49, Rémi Denis-Courmont wrote:
>> So... You say that your debugging environment sucks.
>>
>> That is an argument for you to fix your debugging environment, or use
>
>> another environment.
>
>No because some people are refusing to support building with MSVC.
>Things will hopefully change when we can generate usable PDB files with
>
>CLang.
>
>In the mean time I am forced to use gcc and gdb.
>
>>
>> That is not an argument for adding printf debugging to one specific
>> assertion out of many, which does not solve your problem.
>
>Are you saying this patch doesn't help debug leaks ?
>
>>
>> Le 21 février 2019 13:32:04 GMT+02:00, Steve Lhomme
><robux4 at ycbcr.xyz>
>> a écrit :
>>
>> On 21/02/2019 11:58, Rémi Denis-Courmont wrote:
>>
>> It's making a special snow flake of that one specific
>> assertion. If you want to develop tooling for dumping the
>> object tree, you're much better off scripting your favorite
>> debugger than cluttering one specific VLC assertion.
>>
>>
>> I don't think that's possible in QtCreator (and that's not my
>favorite
>> debugger by far), while writing a few lines of code in C is very
>easy.
>>
>> On Windows gdb doesn't break on asserts. It could be enabled to
>do it,
>> but then everytime I'd run VLC under gdb it breaks 20 times in
>weird Qt
>> places. So I always end up disabling it. So when a leak occurs
>(or any
>> assert for that matter) I have to go through this and pray I'll
>have the
>> leak/assert again.
>>
>> >
>>
>> Le 21 février 2019 12:44:44 GMT+02:00, Steve Lhomme
>> <robux4 at ycbcr.xyz> a écrit : On 21/02/2019 11:37, Rémi
>> Denis-Courmont wrote: Hi, My GDB skills are bad so I just
>> walked the objects tree by printing memory content on the
>> abort. It would be much easier with VLC-specific GDB macros,
>> but the point is that you can debug that assertion just as
>> any. It also works after the fact for pseudorandom failures,
>> if you enable core dumps. Much better than this patch since
>> you have access to all memory, not just the objects tree.
>> Adding special snow flake debug code for assertion is a bad
>> idea that sets a very bad precedent - as opposed to improving
>> integration with proper debugging tools. What's snow flake
>> about adding debug tooling ? Le 21 février 2019 12:26:47
>> GMT+02:00, Thomas Guillem <thomas at gllm.fr> a écrit : On Thu,
>> Feb 21, 2019, at 11:18, Rémi Denis-Courmont wrote: Hi, Well I
>> did debug that assertion failure using (ASan +) gdb just fine
>> last time. The code has not changed. So this kludge is
>> definitely not necessary for its alleged purpose. Even if it
>> works with gdb (please tell us how), evelopers don't always
>> run VLC with gdb. This cause an issue if the leak is not
>> reproducible... Not only that but stderr is not universally
>> the output for debug nor is it universally where assertion
>> failures are dumped to, So if there is no stderr, you don't
>> see the error. I don't see the problem at all. so this patch
>> does not even work properly Works on Windows, Android, Linux,
>> macOS when VLC is run via command line. This is the case for
>> most developers usecase. And in most cases you can see the
>> leak by stopping all inputs and dumping the objects tree
>> before quitting, anyway. What about leaks not related to
>> playback ? Interface, service discovery, playlist that are
>> only cleaned when vlc is closed. Le 21 février 2019 11:24:57
>> GMT+02:00, Thomas Guillem <thomas at gllm.fr> a écrit : Comment:
>> A lot of developers asked me to propose this patch again. It
>> was previously refused because developers could use proper
>> debugging tools. I disagree with that assumption. Even with
>> Asan, when the leak assert fail, it will abort() without
>> prompting any leaks, so you'll have to edit libvlc.c to
>remove
>> this assert. If your leak was not reproducible, you'll lose a
>> precious information. And good luck finding the leak with
>GDB,
>> you really need to know the internal of vlc_object_t to
>> iterate through the different list to get the culprit. Commit
>> log: In case of a vlc_object_t leak, and if asserts are
>> enabled, the error output will be like the following (when
>> leaking intentionally decoder_t objects): === vlc_object
>LEAKS
>> detected === \ playlist | \ input | | \ decoder avcodec | | |
>> decoder faad | | | decoder stl
>>
>------------------------------------------------------------------------
>> src/libvlc.c | 30 ++++++++++++++++++++++++++++++ 1 file
>> changed, 30 insertions(+) diff --git a/src/libvlc.c
>> b/src/libvlc.c index 8e8d2ca8b2..d9ff96de84 100644 ---
>> a/src/libvlc.c +++ b/src/libvlc.c @@ -436,6 +436,24 @@ void
>> libvlc_InternalCleanup( libvlc_int_t *p_libvlc ) #endif }
>> +#ifndef NDEBUG +static void
>> DumpObjectLeaks(vlc_object_internals_t *priv, unsigned level)
>> +{ + bool first = true; + vlc_list_foreach(priv,
>> &priv->children, siblings) + { + vlc_object_t *obj =
>> vlc_externals(priv); + for (unsigned i = 0; i < level; i++) +
>> fprintf(stderr, " %s ", first && i == level -1 ? "\\" : "|");
>> + char *name = vlc_object_get_name(obj); + fprintf(stderr,
>"%s
>> %s\n", vlc_object_typename(obj), name ? name : ""); +
>> free(name); + DumpObjectLeaks(priv, level + 1); + first =
>> false; + } +} +#endif + /** * Destroy everything. * This
>> function requests the running threads to finish, waits for
>> their @@ -449,6 +467,18 @@ void libvlc_InternalDestroy(
>> libvlc_int_t *p_libvlc ) vlc_ExitDestroy( &priv->exit );
>> +#ifndef NDEBUG + { + vlc_object_internals_t *internal =
>> vlc_internals(p_libvlc); + if (atomic_load(&internal->refs)
>!=
>> 1) + { + vlc_mutex_lock(&internal->tree_lock); +
>> fprintf(stderr, "=== vlc_object LEAKS detected ===\n"); +
>> DumpObjectLeaks(internal, 1); +
>> vlc_mutex_unlock(&internal->tree_lock); + } + } +#endif
>> assert( atomic_load(&(vlc_internals(p_libvlc)->refs)) == 1 );
>> vlc_object_release( p_libvlc ); } -- Envoyé de mon appareil
>> Android avec Courriel K-9 Mail. Veuillez excuser ma brièveté.
>>
>------------------------------------------------------------------------
>> vlc-devel mailing list To unsubscribe or modify your
>> subscription options:
>> https://mailman.videolan.org/listinfo/vlc-devel -- Envoyé de
>> mon appareil Android avec Courriel K-9 Mail. Veuillez excuser
>> ma brièveté.
>>
>------------------------------------------------------------------------
>> vlc-devel mailing list To unsubscribe or modify your
>> subscription options:
>> https://mailman.videolan.org/listinfo/vlc-devel
>>
>------------------------------------------------------------------------
>> vlc-devel mailing list To unsubscribe or modify your
>> subscription options:
>> https://mailman.videolan.org/listinfo/vlc-devel -- Envoyé de
>> mon appareil Android avec Courriel K-9 Mail. Veuillez excuser
>> ma brièveté.
>>
>------------------------------------------------------------------------
>> vlc-devel mailing list To unsubscribe or modify your
>> subscription options:
>> https://mailman.videolan.org/listinfo/vlc-devel
>>
>>
>------------------------------------------------------------------------
>> vlc-devel mailing list
>> To unsubscribe or modify your subscription options:
>> https://mailman.videolan.org/listinfo/vlc-devel
>>
>>
>> --
>> Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez
>> excuser ma brièveté.
>>
>> _______________________________________________
>> vlc-devel mailing list
>> To unsubscribe or modify your subscription options:
>> https://mailman.videolan.org/listinfo/vlc-devel
>
>_______________________________________________
>vlc-devel mailing list
>To unsubscribe or modify your subscription options:
>https://mailman.videolan.org/listinfo/vlc-devel
--
Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez excuser ma brièveté.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/vlc-devel/attachments/20190221/898551c4/attachment.html>
More information about the vlc-devel
mailing list