fix: guard asyncify_stop_unwind() for async web API import unwinds (i…

stubs/runtime.c

@@ -3,6 +3,9 @@
 #include "setjmp.h"
 #include <stdlib.h>
 
+/* defined in setjmp.c; set by asyncify_start_unwind macro, cleared by asyncify_stop_unwind macro */
+extern void *pl_asyncify_unwind_buf;
+
 int asyncjmp_rt_start(int(main)(int argc, char **argv), int argc, char **argv)
 {
     int result;
@@ -12,29 +15,44 @@ int asyncjmp_rt_start(int(main)(int argc, char **argv), int argc, char **argv)
     {
         result = main(argc, argv);
 
-         extern void *pl_asyncify_unwind_buf;
-        // Exit Asyncify loop if there is no unwound buffer, which
-        // means that main function has returned normally.
-        if (pl_asyncify_unwind_buf == NULL) {
-          break;
-        }
-
-        // NOTE: it's important to call 'asyncify_stop_unwind' here instead in
-        // asyncjmp_handle_jmp_unwind because unless that, Asyncify inserts another
-        // unwind check here and it unwinds to the root frame.
-        asyncify_stop_unwind();
-
-        if ((asyncify_buf = asyncjmp_handle_jmp_unwind()) != NULL)
+        /*
+         * Only call asyncify_stop_unwind() when this was a C-level unwind
+         * initiated by zeroperl's own asyncify_start_unwind() macro.
+         * The macro sets pl_asyncify_unwind_buf; asyncify import handling does not.
+         *
+         * If pl_asyncify_unwind_buf == NULL and main() returned, we are either:
+         *   (a) Normal Perl exit: __asyncify_state == 0. Break normally.
+         *   (b) Asyncify-import unwind (async web API via call_host_function):
+         *       __asyncify_state == 1 (UNWINDING). Do NOT clear it here.
+         *       Let it propagate so the JS host detects state == 1, awaits
+         *       the Promise, calls asyncify_start_rewind(), and re-invokes
+         *       the export to complete the rewind.
+         */
+        if (pl_asyncify_unwind_buf != NULL)
         {
-            asyncify_start_rewind(asyncify_buf);
-            continue;
-        }
-        if ((asyncify_buf = asyncjmp_handle_scan_unwind()) != NULL)
-        {
-            asyncify_start_rewind(asyncify_buf);
-            continue;
+            /*
+             * C-level unwind (setjmp / longjmp / GC scan).
+             * NOTE: asyncify_stop_unwind() must be called here (in the loop),
+             * not inside the handler functions, or Asyncify inserts another
+             * unwind check here and unwinds to the root frame.
+             */
+            asyncify_stop_unwind();
+
+            if ((asyncify_buf = asyncjmp_handle_jmp_unwind()) != NULL)
+            {
+                asyncify_start_rewind(asyncify_buf);
+                continue;
+            }
+            if ((asyncify_buf = asyncjmp_handle_scan_unwind()) != NULL)
+            {
+                asyncify_start_rewind(asyncify_buf);
+                continue;
+            }
+            /* pl_asyncify_unwind_buf was set but no handler claimed it */
+            break;
         }
 
+        /* Normal exit or async import unwind */
         break;
     }
     return result;