[vlc-devel] [PATCH 2/2] configure: split dynamic plugins from dynamic loader
Alexandre Janniaux
ajanni at videolabs.io
Fri Mar 6 10:18:04 CET 2020
Hi,
Actually, this is not complete yet, as vlc_static_modules
is not defined, so there is no benefit to using VLC_WEAK.
I'll fix that in a new patchset, feel free to review those
two patches though.
Regards,
--
Alexandre Janniaux
Videolabs
On Thu, Mar 05, 2020 at 07:25:26PM +0100, Alexandre Janniaux wrote:
> As we can embed static and dynamic plugins at the same time, it makes
> sense to build LibVLC-provided modules inside VLC but still allow
> external out-of-tree plugins to be added later.
>
> It allows extending LibVLC through the dynamic loader while keeping the
> official binaries, which make sense on iOS and Android. Indeed, on those
> platform, shared library are either limited (support since iOS 8/9 on
> one side and limit to 128 shared objects including system libraries on
> the other side until API 23 [1] thanks to patch [2]) or with a
> non-negligeable performance cost.
>
> It is also much better than providing a plugin interface in which you
> merge all modules from LibVLC and force the use of the dynamic loader as
> the current inheritance mechanism doesn't play nicely with such
> construction, and current buildsystem for Android and iOS are conceived
> for static builds.
>
> [1] https://android.googlesource.com/platform/bionic/+/android-n-mr2-preview-1/android-changes-for-ndk-developers.md
> [2] https://android.googlesource.com/platform/bionic/+/ba98d9237b0eabc1d8caf2600fd787b988645249%5E%21/
> ---
> configure.ac | 17 +++++++++++++++++
> src/Makefile.am | 3 +++
> src/libvlc-module.c | 4 ++--
> src/modules/bank.c | 10 +++++-----
> src/modules/cache.c | 4 ++--
> src/modules/entry.c | 8 ++++----
> src/modules/modules.h | 2 +-
> 7 files changed, 34 insertions(+), 14 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index bc1874cb97..925772f87c 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -869,11 +869,28 @@ AS_VAR_IF(with_libfuzzer, no, [], [
> ])
> AM_CONDITIONAL([HAVE_LIBFUZZER], [test "${with_libfuzzer}" != "no"])
>
> +dnl
> +dnl When building dynamic objects only, both the dynamic plugin and the
> +dnl dynamic loader are built. When building static plugins, the dynamic
> +dnl loader can be specifically enabled or not using --enable-dynamic-loader.
> +dnl
> AS_IF([test "${enable_shared}" = "no"], [
> have_dynamic_objects=no
> ])
> AM_CONDITIONAL([HAVE_DYNAMIC_PLUGINS], [test "${have_dynamic_objects}" != "no"])
>
> +AC_ARG_ENABLE([dynamic-loader],
> + AS_HELP_STRING([--enable-dynamic-loader],
> + [compile VLC with dynamic plugin loader, only makes sense for static build (default disabled for static build)]))
> +
> +have_dynamic_loader="no"
> +AS_IF([test "${enable_dynamic_loader}" = "yes"], [have_dynamic_loader="yes"])
> +AM_CONDITIONAL([HAVE_DYNAMIC_LOADER],
> + [test "${have_dynamic_loader}" = "yes" -o "${have_dynamic_objects}" = "yes"])
> +
> +AS_IF([test "${enable_shared}" != "no" -a "${enable_dynamic_loader}" = "no"], [
> + AC_MSG_ERROR([Dynamic loaders cannot be disabled when building dynamic plugins.])])
> +
> AC_SUBST([LIBDL])
>
> AS_IF([test "${SYS}" != "mingw32"], [
> diff --git a/src/Makefile.am b/src/Makefile.am
> index 2b4dfcb7dd..d19bd47d93 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -187,6 +187,9 @@ AM_CFLAGS = $(CFLAGS_libvlccore)
> if HAVE_DYNAMIC_PLUGINS
> AM_CPPFLAGS += -DHAVE_DYNAMIC_PLUGINS
> endif
> +if HAVE_DYNAMIC_LOADER
> +AM_CPPFLAGS += -DHAVE_DYNAMIC_LOADER
> +endif
> if HAVE_DBUS
> AM_CPPFLAGS += -DHAVE_DBUS
> AM_CFLAGS += $(DBUS_CFLAGS)
> diff --git a/src/libvlc-module.c b/src/libvlc-module.c
> index 1da7fa6e79..8f255a1766 100644
> --- a/src/libvlc-module.c
> +++ b/src/libvlc-module.c
> @@ -2152,7 +2152,7 @@ vlc_module_begin ()
> VOD_SERVER_TEXT, VOD_SERVER_LONGTEXT)
>
> set_section( N_("Plugins" ), NULL )
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> add_bool( "plugins-cache", true, PLUGINS_CACHE_TEXT,
> PLUGINS_CACHE_LONGTEXT, true )
> change_volatile ()
> @@ -2918,7 +2918,7 @@ vlc_module_begin ()
> add_obsolete_bool( "save-config" )
> add_bool( "reset-config", false, RESET_CONFIG_TEXT, "", false )
> change_volatile ()
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> add_bool( "reset-plugins-cache", false,
> RESET_PLUGINS_CACHE_TEXT, "", false )
> change_volatile ()
> diff --git a/src/modules/bank.c b/src/modules/bank.c
> index e8c956ebe6..7dbad48856 100644
> --- a/src/modules/bank.c
> +++ b/src/modules/bank.c
> @@ -165,14 +165,14 @@ static vlc_plugin_t *module_InitStatic(vlc_plugin_cb entry)
> if (unlikely(lib == NULL))
> return NULL;
>
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> atomic_init(&lib->handle, 0);
> lib->unloadable = false;
> #endif
> return lib;
> }
>
> -#if defined(__ELF__) || defined(__MACH__) || !HAVE_DYNAMIC_PLUGINS
> +#if defined(__ELF__) || defined(__MACH__) || !HAVE_DYNAMIC_LOADER
> VLC_WEAK
> extern vlc_plugin_cb vlc_static_modules[];
>
> @@ -192,7 +192,7 @@ static void module_InitStaticModules(void)
> static void module_InitStaticModules(void) { }
> #endif
>
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> static const char *module_GetVersion(void *handle)
> {
> const char *(*get_api_version)(void);
> @@ -629,7 +629,7 @@ void *module_Symbol(struct vlc_logger *log,
> (void) log; (void) plugin; (void) name;
> return NULL;
> }
> -#endif /* HAVE_DYNAMIC_PLUGINS */
> +#endif /* HAVE_DYNAMIC_LOADER */
>
> /**
> * Init bank
> @@ -723,7 +723,7 @@ void module_LoadPlugins(vlc_object_t *obj)
> if (modules.usage == 1)
> {
> module_InitStaticModules ();
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> msg_Dbg (obj, "searching plug-in modules");
> AllocateAllPlugins (obj);
> #endif
> diff --git a/src/modules/cache.c b/src/modules/cache.c
> index c1428bd9f5..8493a8c287 100644
> --- a/src/modules/cache.c
> +++ b/src/modules/cache.c
> @@ -53,7 +53,7 @@
> /*****************************************************************************
> * Local prototypes
> *****************************************************************************/
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> /* Sub-version number
> * (only used to avoid breakage in dev version when cache structure changes) */
> #define CACHE_SUBVERSION_NUM 36
> @@ -707,4 +707,4 @@ vlc_plugin_t *vlc_cache_lookup(vlc_plugin_t **cache, const char *path)
>
> return NULL;
> }
> -#endif /* HAVE_DYNAMIC_PLUGINS */
> +#endif /* HAVE_DYNAMIC_LOADER */
> diff --git a/src/modules/entry.c b/src/modules/entry.c
> index 70f9a8c932..a5eb36aee3 100644
> --- a/src/modules/entry.c
> +++ b/src/modules/entry.c
> @@ -103,7 +103,7 @@ vlc_plugin_t *vlc_plugin_create(void)
> plugin->conf.size = 0;
> plugin->conf.count = 0;
> plugin->conf.booleans = 0;
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> plugin->abspath = NULL;
> plugin->unloadable = true;
> atomic_init(&plugin->handle, 0);
> @@ -123,7 +123,7 @@ vlc_plugin_t *vlc_plugin_create(void)
> void vlc_plugin_destroy(vlc_plugin_t *plugin)
> {
> assert(plugin != NULL);
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> assert(!plugin->unloadable || atomic_load(&plugin->handle) == 0);
> #endif
>
> @@ -131,7 +131,7 @@ void vlc_plugin_destroy(vlc_plugin_t *plugin)
> vlc_module_destroy(plugin->module);
>
> config_Free(plugin->conf.items, plugin->conf.size);
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> free(plugin->abspath);
> free(plugin->path);
> #endif
> @@ -278,7 +278,7 @@ static int vlc_plugin_desc_cb(void *ctx, void *tgt, int propid, ...)
> break;
>
> case VLC_MODULE_NO_UNLOAD:
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> plugin->unloadable = false;
> #endif
> break;
> diff --git a/src/modules/modules.h b/src/modules/modules.h
> index 264b40344c..5785ba544d 100644
> --- a/src/modules/modules.h
> +++ b/src/modules/modules.h
> @@ -45,7 +45,7 @@ typedef struct vlc_plugin_t
> size_t booleans; /**< Number of booleal config items */
> } conf;
>
> -#ifdef HAVE_DYNAMIC_PLUGINS
> +#ifdef HAVE_DYNAMIC_LOADER
> bool unloadable; /**< Whether the plug-in can be unloaded safely */
> atomic_uintptr_t handle; /**< Run-time linker handle (or nul) */
> char *abspath; /**< Absolute path */
> --
> 2.25.1
>
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