[FFmpeg-devel] [PATCH v2] avformat/avio: Don't use incompatible function pointer type for call

[Andreas Rheinhardt]

It is undefined behaviour even in cases where it works
(it works because it is only a const uint8_t* vs. uint8_t* difference).
Instead use a macro to produce two functions with the required
types to be const-correct and type-safe.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
---
 libavformat/avio.c | 98 +++++++++++++++++++++++-----------------------
 1 file changed, 50 insertions(+), 48 deletions(-)

diff --git a/libavformat/avio.c b/libavformat/avio.c
index ab1c19a58d..9783cb1881 100644
--- a/libavformat/avio.c
+++ b/libavformat/avio.c
@@ -353,63 +353,67 @@ fail:
     return ret;
 }
 
-static inline int retry_transfer_wrapper(URLContext *h, uint8_t *buf,
-                                         int size, int size_min,
-                                         int (*transfer_func)(URLContext *h,
-                                                              uint8_t *buf,
-                                                              int size))
-{
-    int ret, len;
-    int fast_retries = 5;
-    int64_t wait_since = 0;
-
-    len = 0;
-    while (len < size_min) {
-        if (ff_check_interrupt(&h->interrupt_callback))
-            return AVERROR_EXIT;
-        ret = transfer_func(h, buf + len, size - len);
-        if (ret == AVERROR(EINTR))
-            continue;
-        if (h->flags & AVIO_FLAG_NONBLOCK)
-            return ret;
-        if (ret == AVERROR(EAGAIN)) {
-            ret = 0;
-            if (fast_retries) {
-                fast_retries--;
-            } else {
-                if (h->rw_timeout) {
-                    if (!wait_since)
-                        wait_since = av_gettime_relative();
-                    else if (av_gettime_relative() > wait_since + h->rw_timeout)
-                        return AVERROR(EIO);
-                }
-                av_usleep(1000);
-            }
-        } else if (ret == AVERROR_EOF)
-            return (len > 0) ? len : AVERROR_EOF;
-        else if (ret < 0)
-            return ret;
-        if (ret) {
-            fast_retries = FFMAX(fast_retries, 2);
-            wait_since = 0;
-        }
-        len += ret;
-    }
-    return len;
+#define RETRY_TRANSFER_WRAPPER(RW, CONST)                                     \
+static inline int retry_ ## RW ## _wrapper(URLContext *h, CONST uint8_t *buf, \
+                                           int size, int size_min,            \
+                                           int (*RW ## _func)(URLContext *h,  \
+                                                              CONST uint8_t *buf, \
+                                                              int size))      \
+{                                                                             \
+    int ret, len;                                                             \
+    int fast_retries = 5;                                                     \
+    int64_t wait_since = 0;                                                   \
+                                                                              \
+    len = 0;                                                                  \
+    while (len < size_min) {                                                  \
+        if (ff_check_interrupt(&h->interrupt_callback))                       \
+            return AVERROR_EXIT;                                              \
+        ret = RW ## _func(h,  buf + len, size - len);                         \
+        if (ret == AVERROR(EINTR))                                            \
+            continue;                                                         \
+        if (h->flags & AVIO_FLAG_NONBLOCK)                                    \
+            return ret;                                                       \
+        if (ret == AVERROR(EAGAIN)) {                                         \
+            ret = 0;                                                          \
+            if (fast_retries) {                                               \
+                fast_retries--;                                               \
+            } else {                                                          \
+                if (h->rw_timeout) {                                          \
+                    if (!wait_since)                                          \
+                        wait_since = av_gettime_relative();                   \
+                    else if (av_gettime_relative() > wait_since + h->rw_timeout) \
+                        return AVERROR(EIO);                                  \
+                }                                                             \
+                av_usleep(1000);                                              \
+            }                                                                 \
+        } else if (ret == AVERROR_EOF)                                        \
+            return (len > 0) ? len : AVERROR_EOF;                             \
+        else if (ret < 0)                                                     \
+            return ret;                                                       \
+        if (ret) {                                                            \
+            fast_retries = FFMAX(fast_retries, 2);                            \
+            wait_since = 0;                                                   \
+        }                                                                     \
+        len += ret;                                                           \
+    }                                                                         \
+    return len;                                                               \
 }
 
+RETRY_TRANSFER_WRAPPER(read, )
+RETRY_TRANSFER_WRAPPER(write, const)
+
 int ffurl_read(URLContext *h, unsigned char *buf, int size)
 {
     if (!(h->flags & AVIO_FLAG_READ))
         return AVERROR(EIO);
-    return retry_transfer_wrapper(h, buf, size, 1, h->prot->url_read);
+    return retry_read_wrapper(h, buf, size, 1, h->prot->url_read);
 }
 
 int ffurl_read_complete(URLContext *h, unsigned char *buf, int size)
 {
     if (!(h->flags & AVIO_FLAG_READ))
         return AVERROR(EIO);
-    return retry_transfer_wrapper(h, buf, size, size, h->prot->url_read);
+    return retry_read_wrapper(h, buf, size, size, h->prot->url_read);
 }
 
 int ffurl_write(URLContext *h, const unsigned char *buf, int size)
@@ -420,9 +424,7 @@ int ffurl_write(URLContext *h, const unsigned char *buf, int size)
     if (h->max_packet_size && size > h->max_packet_size)
         return AVERROR(EIO);
 
-    return retry_transfer_wrapper(h, (unsigned char *)buf, size, size,
-                                  (int (*)(struct URLContext *, uint8_t *, int))
-                                  h->prot->url_write);
+    return retry_write_wrapper(h, buf, size, size, h->prot->url_write);
 }
 
 int64_t ffurl_seek(URLContext *h, int64_t pos, int whence)
-- 
2.34.1