decklink_drift_fix: fix allocation

Since the assertion added in 54097db (May 26 2026), msg_universal
constructor doesn't set the magic value, resulting in abort.

Removed the constructor and replaced with a function utilizing
new_message() that is correctly setting this field.

fixes GH-497

Author: MartinPulec

src/messaging.cpp

@@ -331,6 +331,16 @@ struct message *new_message(size_t len)
         return ret;
 }
 
+struct msg_universal *
+new_message_universal(const char *contents)
+{
+        struct msg_universal *msg = nullptr;
+        struct message *m = new_message(sizeof *msg);
+        msg = (struct msg_universal *) m;
+        strcpy_ch(msg->text, contents);
+        return msg;
+}
+
 /**
  * Frees message
  *

src/messaging.h

@@ -67,8 +67,8 @@ struct response;
 
 #define RESPONSE_SUCCESSFUL(code) ((code) >= 200 && (code) < 300)
 
-struct message;
-
+/// message must be allocated with dedicated function - new_message() or
+/// new_message_universal()
 struct message {
         alignas(8) uint32_t magic;
         /**
@@ -148,18 +148,17 @@ struct msg_stats {
  * msg_universal::text to identify the receiving module.
  */
 struct msg_universal {
-#ifdef __cplusplus
-        msg_universal(const char *contents) {
-                memset(&m, 0, sizeof m);
-                strncpy(text, contents, sizeof text - 1);
-        }
-#endif
         struct message m;
         char text[8192];
 };
 
 #define MSG_UNIVERSAL_TAG_TX "TX_msg "
 
+/// allocate new message
+struct message *new_message(size_t length);
+struct msg_universal *new_message_universal(const char *contents);
+void free_message(struct message *m, struct response *r);
+
 struct response *new_response(int status, const char *optional_message);
 void free_response(struct response *r);
 int response_get_status(struct response *r);
@@ -173,8 +172,6 @@ struct response *send_message(struct module *, const char *path, struct message
 #define SEND_MESSAGE_FLAG_NO_STORE (1<<1) ///< if receiver doesn't exist, doesn't store it and return 404 instead
 struct response *send_message_sync(struct module *, const char *path, struct message *msg, int timeout_ms, int flags) __attribute__ ((warn_unused_result));
 struct response *send_message_to_receiver(struct module *, struct message *msg) __attribute__ ((warn_unused_result));
-struct message *new_message(size_t length) __attribute__ ((warn_unused_result));
-void free_message(struct message *m, struct response *r);
 const char *response_status_to_text(int status);
 
 struct message *check_message(struct module *);

src/video_display/decklink_drift_fix.hpp

@@ -4,7 +4,7 @@
  * @author Andrew Walker    <andrew.walker@sohonet.com>
  */
 /*
- * Copyright (c) 2021-2023 CESNET, z. s. p. o.
+ * Copyright (c) 2021-2026 CESNET, zájmové sdružení právnických osob
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -50,6 +50,7 @@
 #include "messaging.h"
 #include "rtp/audio_decoders.h"
 #include "utils/color_out.h"
+#include "utils/macros.h"       // for snprintf_ch
 
 #define MAX_RESAMPLE_DELTA_DEFAULT 30
 #define MIN_RESAMPLE_DELTA_DEFAULT 1
@@ -442,7 +443,11 @@ class AudioDriftFixer {
 
                 if (dst_frame_rate != 0 &&
                     dst_frame_rate != dst_frame_rate_set) {
-                        auto *m = new msg_universal((std::string(MSG_UNIVERSAL_TAG_AUDIO_DECODER) + std::to_string(dst_frame_rate << ADEC_CH_RATE_SHIFT | BASE)).c_str());
+                        char text[128];
+                        snprintf_ch(
+                            text, MSG_UNIVERSAL_TAG_AUDIO_DECODER "%lld",
+                            dst_frame_rate << ADEC_CH_RATE_SHIFT | BASE);
+                        auto *m = new_message_universal(text);
                         LOG(LOG_LEVEL_DEBUG)
                             << MOD_NAME "Sending resample request "
                             << dst_frame_rate << "/" << BASE << "\n";