ggml : Callback before abort (ggml-org#14481)

* Add a callback that will be called just before abort. This allows apps without a console to display a message to the user and save data if needed.

* Return previous callback to allow callback chaining

* style fixes

---------

Co-authored-by: Diego Devesa <slarengh@gmail.com>

Author: 2 people

ggml/src/ggml.c

@@ -202,19 +202,34 @@ void ggml_print_backtrace(void) {
 }
 #endif
 
+static ggml_abort_callback_t g_abort_callback = NULL;
+
+// Set the abort callback (passing null will restore original abort functionality: printing a message to stdout)
+GGML_API ggml_abort_callback_t ggml_set_abort_callback(ggml_abort_callback_t callback) {
+    ggml_abort_callback_t ret_val = g_abort_callback;
+    g_abort_callback = callback;
+    return ret_val;
+}
+
 void ggml_abort(const char * file, int line, const char * fmt, ...) {
     fflush(stdout);
 
-    fprintf(stderr, "%s:%d: ", file, line);
+    char message[2048];
+    int offset = snprintf(message, sizeof(message), "%s:%d: ", file, line);
 
     va_list args;
     va_start(args, fmt);
-    vfprintf(stderr, fmt, args);
+    vsnprintf(message + offset, sizeof(message) - offset, fmt, args);
     va_end(args);
 
-    fprintf(stderr, "\n");
+    if (g_abort_callback) {
+        g_abort_callback(message);
+    } else {
+        // default: print error and backtrace to stderr
+        fprintf(stderr, "%s\n", message);
+        ggml_print_backtrace();
+    }
 
-    ggml_print_backtrace();
     abort();
 }