fix explanation how to obtain the map size

docs/Changelog.md

@@ -39,6 +39,7 @@
       AFL_LLVM_INSTRUMENT=CLASSIC
     - new compile time variable: `AFL_OPT_LEVEL` to set a specific optimization
       level, default is `3`
+    - correctly explain how to get the correct map size for large targets
   - code formatting updated to llvm 18
   - improved custom_mutators/aflpp/standalone/aflpp-standalone
   - added custom_mutators/autotokens/standalone/autotokens-standalone

instrumentation/afl-compiler-rt.o.c

@@ -367,6 +367,12 @@ static void __afl_map_shm(void) {
 
     }
 
+    if (__afl_debug) {
+
+      fprintf(stderr, "DEBUG: AFL_MAP_SIZE=%u\n", __afl_map_size);
+
+    }
+
     if (__afl_final_loc > MAP_SIZE) {
 
       char *ptr;

src/afl-forkserver.c

@@ -495,9 +495,9 @@ static void report_error_and_exit(int error) {
       FATAL(
           "AFL_MAP_SIZE is not set and fuzzing target reports that the "
           "required size is very large. Solution: Run the fuzzing target "
-          "stand-alone with the environment variable AFL_DEBUG=1 set and set "
-          "the value for __afl_final_loc in the AFL_MAP_SIZE environment "
-          "variable for afl-fuzz.");
+          "stand-alone with the environment variable AFL_DUMP_MAP_SIZE=1 set "
+          "the displayed value in the AFL_MAP_SIZE environment variable for "
+          "afl-fuzz.");
       break;
     case FS_ERROR_MAP_ADDR:
       FATAL(