afl_custom_describe api added

include/afl-fuzz.h

@@ -798,6 +798,20 @@ struct custom_mutator {
   size_t (*afl_custom_fuzz)(void *data, u8 *buf, size_t buf_size, u8 **out_buf,
                             u8 *add_buf, size_t add_buf_size, size_t max_size);
 
+  /**
+   * Describe the current testcase, generated by the last mutation.
+   * This will be called, for example, to give the written testcase a name
+   * after a crash ocurred. It can help to reproduce crashing mutations.
+   *
+   * (Optional)
+   *
+   * @param data pointer returned in afl_custom_init for this fuzz case
+   * @param[in] max_size Maximum size of the mutated output. The mutation must
+   * not produce data larger than max_size.
+   * @return A valid ptr to a 0-terminated string, or NULL on error.
+   */
+  const char *(*afl_custom_describe)(void *data, size_t max_size);
+
   /**
    * A post-processing function to use right before AFL writes the test case to
    * disk in order to execute the target.