Re: [FFmpeg-devel] [PATCH 1/6] lavu/mem: add av_realloc_reuse() as a replacement for av_fast_realloc()

["Rémi Denis-Courmont" <remi@remlab.net>]

Le 28 septembre 2022 13:48:49 GMT+03:00, Anton Khirnov <anton@khirnov.net> a écrit :
>It uses size_t rather than unsigned for the size and conforms to our
>standard naming scheme.
>---
> configure           |  5 ++++-
> doc/APIchanges      |  3 +++
> libavutil/mem.c     | 30 ++++++++++++++++++++++++++++++
> libavutil/mem.h     | 37 +++++++++++++++++++++++++++++++++++--
> libavutil/version.h |  3 ++-
> 5 files changed, 74 insertions(+), 4 deletions(-)
>
>diff --git a/configure b/configure
>index 6712d045d9..fd0e6ae032 100755
>--- a/configure
>+++ b/configure
>@@ -4360,7 +4360,10 @@ case "$toolchain" in
>         target_exec_default="valgrind"
>         case "$toolchain" in
>             valgrind-massif)
>-                target_exec_args="--tool=massif --alloc-fn=av_malloc --alloc-fn=av_mallocz --alloc-fn=av_calloc --alloc-fn=av_fast_padded_malloc --alloc-fn=av_fast_malloc --alloc-fn=av_realloc_f --alloc-fn=av_fast_realloc --alloc-fn=av_realloc"
>+                target_exec_args="--tool=massif"
>+                for func in av_malloc av_mallocz av_calloc av_fast_padded_malloc av_fast_malloc av_realloc_f av_fast_realloc av_realloc av_realloc_reuse; do
>+                    target_exec_args="$target_exec_args --alloc-fn=$func"
>+                done
>                 ;;
>             valgrind-memcheck)
>                 target_exec_args="--error-exitcode=1 --malloc-fill=0x2a --track-origins=yes --leak-check=full --gen-suppressions=all --suppressions=$source_path/tests/fate-valgrind.supp"
>diff --git a/doc/APIchanges b/doc/APIchanges
>index b0a41c9e37..9a735c27e7 100644
>--- a/doc/APIchanges
>+++ b/doc/APIchanges
>@@ -14,6 +14,9 @@ libavutil:     2021-04-27
> 
> API changes, most recent first:
> 
>+2022-xx-xx - xxxxxxxxxx - lavu 57.38.100 - mem.h
>+  Add av_realloc_reuse(), deprecate av_fast_realloc().
>+
> 2022-09-26 - xxxxxxxxxx - lavc 59.48.100 - avcodec.h
>   Deprecate avcodec_enum_to_chroma_pos() and avcodec_chroma_pos_to_enum().
>   Use av_chroma_location_enum_to_pos() or av_chroma_location_pos_to_enum()
>diff --git a/libavutil/mem.c b/libavutil/mem.c
>index 18aff5291f..51fdc9155f 100644
>--- a/libavutil/mem.c
>+++ b/libavutil/mem.c
>@@ -502,6 +502,35 @@ void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
>     }
> }
> 
>+void *av_realloc_reuse(void *ptr, size_t *size, size_t min_size)
>+{
>+    size_t max_size;
>+
>+    if (min_size <= *size)
>+        return ptr;
>+
>+    max_size = atomic_load_explicit(&max_alloc_size, memory_order_relaxed);
>+
>+    if (min_size > max_size) {
>+        *size = 0;
>+        return NULL;

Isn't this leaking the existing allocation?

>+    }
>+
>+    min_size = FFMIN(max_size, FFMAX(min_size + min_size / 16 + 32, min_size));
>+
>+    ptr = av_realloc(ptr, min_size);
>+    /* we could set this to the unmodified min_size but this is safer
>+     * if the user lost the ptr and uses NULL now
>+     */
>+    if (!ptr)
>+        min_size = 0;
>+
>+    *size = min_size;
>+
>+    return ptr;
>+}
>+
>+#if FF_API_FAST_ALLOC
> void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
> {
>     size_t max_size;
>@@ -531,6 +560,7 @@ void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
> 
>     return ptr;
> }
>+#endif
> 
> static inline void fast_malloc(void *ptr, unsigned int *size, size_t min_size, int zero_realloc)
> {
>diff --git a/libavutil/mem.h b/libavutil/mem.h
>index d91174196c..deb440ca1a 100644
>--- a/libavutil/mem.h
>+++ b/libavutil/mem.h
>@@ -264,7 +264,7 @@ void *av_mallocz_array(size_t nmemb, size_t size) av_malloc_attrib av_alloc_size
>  * @warning Unlike av_malloc(), the returned pointer is not guaranteed to be
>  *          correctly aligned. The returned pointer must be freed after even
>  *          if size is zero.
>- * @see av_fast_realloc()
>+ * @see av_realloc_reuse()
>  * @see av_reallocp()
>  */
> void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
>@@ -346,6 +346,35 @@ av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size)
>  */
> int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
> 
>+/**
>+ * Reallocate a data buffer, reusing the existing one if it is large enough.
>+ *
>+ * This function is similar to av_realloc(), but optimized for cases where the
>+ * buffer may grow significantly and is not expected to shrink.
>+ *
>+ * @param[in] ptr Previously allocated buffer, or `NULL`. If `ptr` is `NULL`, a
>+ * new uninitialized buffer is allocated. `ptr` is invalidated when this
>+ * function returns non-`NULL` and must be replaced with its return value.
>+ *
>+ * @param[in,out] size Pointer to the allocated size of buffer `ptr`. This
>+ * function updates `*size` to the new allocated size (which may be larger than
>+ * `min_size`). `*size` is set to 0 on failure.
>+ *
>+ * @param[in] min_size Minimum size in bytes of the returned buffer.
>+ *
>+ * @return
>+ * - An allocated buffer (to be freed with `av_free()`) that is large enough to
>+ *   hold at least `min_size` bytes. The first `*size` (value on entry to this
>+ *   function) bytes of the buffer remain the same as the data in `ptr`, the
>+ *   rest is uninitialized.
>+ * - `NULL` on failure, then `*size` is set to 0 and ptr remains untouched.
>+ *
>+ * @see av_realloc()
>+ * @see av_fast_malloc()
>+ */
>+void *av_realloc_reuse(void *ptr, size_t *size, size_t min_size);
>+
>+#if FF_API_FAST_ALLOC
> /**
>  * Reallocate the given buffer if it is not large enough, otherwise do nothing.
>  *
>@@ -377,13 +406,17 @@ int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
>  *         error
>  * @see av_realloc()
>  * @see av_fast_malloc()
>+ *
>+ * @deprecated use av_realloc_reuse()
>  */
>+attribute_deprecated
> void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
>+#endif
> 
> /**
>  * Allocate a buffer, reusing the given one if large enough.
>  *
>- * Contrary to av_fast_realloc(), the current buffer contents might not be
>+ * Contrary to av_realloc_reuse(), the current buffer contents might not be
>  * preserved and on error the old buffer is freed, thus no special handling to
>  * avoid memleaks is necessary.
>  *
>diff --git a/libavutil/version.h b/libavutil/version.h
>index 9c44cef6aa..285a32f3d6 100644
>--- a/libavutil/version.h
>+++ b/libavutil/version.h
>@@ -79,7 +79,7 @@
>  */
> 
> #define LIBAVUTIL_VERSION_MAJOR  57
>-#define LIBAVUTIL_VERSION_MINOR  37
>+#define LIBAVUTIL_VERSION_MINOR  38
> #define LIBAVUTIL_VERSION_MICRO 100
> 
> #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
>@@ -115,6 +115,7 @@
> #define FF_API_OLD_CHANNEL_LAYOUT       (LIBAVUTIL_VERSION_MAJOR < 58)
> #define FF_API_AV_FOPEN_UTF8            (LIBAVUTIL_VERSION_MAJOR < 58)
> #define FF_API_PKT_DURATION             (LIBAVUTIL_VERSION_MAJOR < 58)
>+#define FF_API_FAST_ALLOC               (LIBAVUTIL_VERSION_MAJOR < 58)
> 
> /**
>  * @}

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