[FFmpeg-devel] [PATCH 10/10] avformat/rtmpproto: guard usage of undefined functions with preprocessor

Kacper Michajłow kasper93 at gmail.com
Tue Jul 22 22:16:11 EEST 2025


The asumption is that DCE will remove references to those functions.
However some compilers with certain instrumentation enabled doesn't DCE
those at all, resulting in linking failure. Tested with cl.exe -RTCu -RTCs.

Signed-off-by: Kacper Michajłow <kasper93 at gmail.com>
---
 libavformat/rtmpproto.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/libavformat/rtmpproto.c b/libavformat/rtmpproto.c
index dd850f72ed..a22db265fc 100644
--- a/libavformat/rtmpproto.c
+++ b/libavformat/rtmpproto.c
@@ -1265,7 +1265,8 @@ static int rtmp_handshake(URLContext *s, RTMPContext *rt)
     for (i = 9; i <= RTMP_HANDSHAKE_PACKET_SIZE; i++)
         tosend[i] = av_lfg_get(&rnd) >> 24;
 
-    if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
+#if CONFIG_FFRTMPCRYPT_PROTOCOL
+    if (rt->encrypted) {
         /* When the client wants to use RTMPE, we have to change the command
          * byte to 0x06 which means to use encrypted data and we have to set
          * the flash version to at least 9.0.115.0. */
@@ -1280,6 +1281,7 @@ static int rtmp_handshake(URLContext *s, RTMPContext *rt)
         if ((ret = ff_rtmpe_gen_pub_key(rt->stream, tosend + 1)) < 0)
             return ret;
     }
+#endif
 
     client_pos = rtmp_handshake_imprint_with_digest(tosend + 1, rt->encrypted);
     if (client_pos < 0)
@@ -1343,7 +1345,8 @@ static int rtmp_handshake(URLContext *s, RTMPContext *rt)
         if (ret < 0)
             return ret;
 
-        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
+#if CONFIG_FFRTMPCRYPT_PROTOCOL
+        if (rt->encrypted) {
             /* Compute the shared secret key sent by the server and initialize
              * the RC4 encryption. */
             if ((ret = ff_rtmpe_compute_secret_key(rt->stream, serverdata + 1,
@@ -1353,6 +1356,7 @@ static int rtmp_handshake(URLContext *s, RTMPContext *rt)
             /* Encrypt the signature received by the server. */
             ff_rtmpe_encrypt_sig(rt->stream, signature, digest, serverdata[0]);
         }
+#endif
 
         if (memcmp(signature, clientdata + RTMP_HANDSHAKE_PACKET_SIZE - 32, 32)) {
             av_log(s, AV_LOG_ERROR, "Signature mismatch\n");
@@ -1373,25 +1377,30 @@ static int rtmp_handshake(URLContext *s, RTMPContext *rt)
         if (ret < 0)
             return ret;
 
-        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
+#if CONFIG_FFRTMPCRYPT_PROTOCOL
+        if (rt->encrypted) {
             /* Encrypt the signature to be send to the server. */
             ff_rtmpe_encrypt_sig(rt->stream, tosend +
                                  RTMP_HANDSHAKE_PACKET_SIZE - 32, digest,
                                  serverdata[0]);
         }
+#endif
 
         // write reply back to the server
         if ((ret = ffurl_write(rt->stream, tosend,
                                RTMP_HANDSHAKE_PACKET_SIZE)) < 0)
             return ret;
 
-        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
+#if CONFIG_FFRTMPCRYPT_PROTOCOL
+        if (rt->encrypted) {
             /* Set RC4 keys for encryption and update the keystreams. */
             if ((ret = ff_rtmpe_update_keystream(rt->stream)) < 0)
                 return ret;
         }
+#endif
     } else {
-        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
+#if CONFIG_FFRTMPCRYPT_PROTOCOL
+        if (rt->encrypted) {
             /* Compute the shared secret key sent by the server and initialize
              * the RC4 encryption. */
             if ((ret = ff_rtmpe_compute_secret_key(rt->stream, serverdata + 1,
@@ -1404,16 +1413,19 @@ static int rtmp_handshake(URLContext *s, RTMPContext *rt)
                                      serverdata[0]);
             }
         }
+#endif
 
         if ((ret = ffurl_write(rt->stream, serverdata + 1,
                                RTMP_HANDSHAKE_PACKET_SIZE)) < 0)
             return ret;
 
-        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
+#if CONFIG_FFRTMPCRYPT_PROTOCOL
+        if (rt->encrypted) {
             /* Set RC4 keys for encryption and update the keystreams. */
             if ((ret = ff_rtmpe_update_keystream(rt->stream)) < 0)
                 return ret;
         }
+#endif
     }
 
     return 0;
-- 
2.50.1



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