wasi_thread_start: add a comment (#371)

diff --git a/libc-top-half/musl/src/thread/pthread_create.c b/libc-top-half/musl/src/thread/pthread_create.c
index 12fccc7a7e223ffa0b5620e518223ab906ec381c..602d503d7d20770a324415fb502cd4ddce2c24dd 100644 (file)
--- a/libc-top-half/musl/src/thread/pthread_create.c
+++ b/libc-top-half/musl/src/thread/pthread_create.c
@@ -277,6 +277,11 @@ static int start_c11(void *p)
 __attribute__((export_name("wasi_thread_start")))
 void wasi_thread_start(int tid, void *p)
 {
+       /*
+        * Note: it's fragile to implement wasi_thread_start in C.
+        * On entry, we don't even have C stack (__stack_pointer)
+        * set up. Be careful when modifying this function.
+        */
        struct start_args *args = p;
        __asm__(".globaltype __tls_base, i32\n"
                        "local.get %0\n"