[vlc-devel] [PATCH 5/5] libvlc: add a function to release strings allocated by libvlc functions

[Rémi Denis-Courmont]

Hi,

If you are going to change how plain strings are returned, I think first should be revisited whether the string should be a copy at all.

It looks to me that, in most case, we should just return a 'const char *' whose lifetime is the same as the input object, or until the object is modified. Thus we eliminate error cases *and* heap problems.

And the marquee getter can probably be removed completely. It's rather schizophrenic to query what is the marquee text that you just set. Probably never used in real life.

Le 24 mai 2019 12:47:31 GMT+03:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>---
> include/vlc/libvlc.h              | 8 ++++++++
> include/vlc/libvlc_media.h        | 2 ++
> include/vlc/libvlc_media_player.h | 7 +++++--
> lib/core.c                        | 5 +++++
> lib/libvlc.sym                    | 1 +
> 5 files changed, 21 insertions(+), 2 deletions(-)
>
>diff --git a/include/vlc/libvlc.h b/include/vlc/libvlc.h
>index 0ec0045c96..789b881f55 100644
>--- a/include/vlc/libvlc.h
>+++ b/include/vlc/libvlc.h
>@@ -277,6 +277,14 @@ LIBVLC_API const char * libvlc_get_compiler(void);
>  */
> LIBVLC_API const char * libvlc_get_changeset(void);
> 
>+/**
>+ * Frees a string returned by a LibVLC function.
>+ *
>+ * \param ptr the string pointer
>+ * \version LibVLC 4.0.0 and later
>+ */
>+LIBVLC_API void libvlc_free_string( char *ptr );
>+
> /** \defgroup libvlc_event LibVLC asynchronous events
>  * LibVLC emits asynchronous events.
>  *
>diff --git a/include/vlc/libvlc_media.h b/include/vlc/libvlc_media.h
>index cd335a6e08..c72e026106 100644
>--- a/include/vlc/libvlc_media.h
>+++ b/include/vlc/libvlc_media.h
>@@ -548,6 +548,7 @@ LIBVLC_API void libvlc_media_release(
>libvlc_media_t *p_md );
>  *
>  * \param p_md a media descriptor object
>  * \return string with mrl of media descriptor object
>+ *         (it result must be released \ref with
>libvlc_free_string()).
>  */
> LIBVLC_API char *libvlc_media_get_mrl( libvlc_media_t *p_md );
> 
>@@ -572,6 +573,7 @@ LIBVLC_API libvlc_media_t *libvlc_media_duplicate(
>libvlc_media_t *p_md );
>  * \param p_md the media descriptor
>  * \param e_meta the meta to read
>  * \return the media's meta
>+ *         (it result must be released \ref with
>libvlc_free_string()).
>  */
> LIBVLC_API char *libvlc_media_get_meta( libvlc_media_t *p_md,
>                                              libvlc_meta_t e_meta );
>diff --git a/include/vlc/libvlc_media_player.h
>b/include/vlc/libvlc_media_player.h
>index f4981cecbc..5f46cb3048 100644
>--- a/include/vlc/libvlc_media_player.h
>+++ b/include/vlc/libvlc_media_player.h
>@@ -1491,7 +1491,7 @@ LIBVLC_API void libvlc_video_set_scale(
>libvlc_media_player_t *p_mi, float f_fac
>  *
>  * \param p_mi the media player
>  * \return the video aspect ratio or NULL if unspecified
>- * (the result must be released with free()).
>+ *         (it result must be released \ref with
>libvlc_free_string()).
>  */
>LIBVLC_API char *libvlc_video_get_aspect_ratio( libvlc_media_player_t
>*p_mi );
> 
>@@ -1661,6 +1661,7 @@ void libvlc_chapter_descriptions_release(
>libvlc_chapter_description_t **p_chapt
>  *
>  * \param p_mi the media player
>  * \return the crop filter geometry or NULL if unset
>+ *         (it result must be released \ref with
>libvlc_free_string()).
>  */
>LIBVLC_API char *libvlc_video_get_crop_geometry( libvlc_media_player_t
>*p_mi );
> 
>@@ -1776,6 +1777,8 @@ LIBVLC_API int libvlc_video_get_marquee_int(
>libvlc_media_player_t *p_mi,
>  *
>  * \param p_mi libvlc media player
>  * \param option marq option to get \see libvlc_video_marquee_option_t
>+ * \return the string corresponding to the marquee option
>+ *         (it result must be released with libvlc_free_string()).
>  */
>LIBVLC_API char *libvlc_video_get_marquee_string( libvlc_media_player_t
>*p_mi,
>                                                     unsigned option );
>@@ -2086,7 +2089,7 @@ LIBVLC_API void libvlc_audio_output_device_set(
>libvlc_media_player_t *mp,
>  * \param mp media player
>  * \return the current audio output device identifier
>  *         NULL if no device is selected or in case of error
>- *         (the result must be released with free()).
>+ *         (the result must be released \ref with
>libvlc_free_string()).
>  * \version LibVLC 3.0.0 or later.
>  */
>LIBVLC_API char *libvlc_audio_output_device_get( libvlc_media_player_t
>*mp );
>diff --git a/lib/core.c b/lib/core.c
>index 6edf14b154..f5af61e459 100644
>--- a/lib/core.c
>+++ b/lib/core.c
>@@ -151,6 +151,11 @@ const char * libvlc_get_changeset(void)
>     return psz_vlc_changeset;
> }
> 
>+void libvlc_free_string( void *ptr )
>+{
>+    free( ptr );
>+}
>+
> static libvlc_module_description_t *module_description_list_get(
>                libvlc_instance_t *p_instance, const char *capability )
> {
>diff --git a/lib/libvlc.sym b/lib/libvlc.sym
>index 436681a4c3..15c777b00a 100644
>--- a/lib/libvlc.sym
>+++ b/lib/libvlc.sym
>@@ -49,6 +49,7 @@ libvlc_dialog_set_callbacks
> libvlc_dialog_set_context
> libvlc_event_attach
> libvlc_event_detach
>+libvlc_free_string
> libvlc_get_changeset
> libvlc_get_compiler
> libvlc_get_fullscreen
>-- 
>2.17.1
>
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