From 9bec2d3aff198770e98544cb6f13add60e1f5fe6 Mon Sep 17 00:00:00 2001
From: Cheng Shao <astrohavoc@gmail.com>
Date: Mon, 30 Jan 2023 13:30:02 +0100
Subject: [PATCH] Add a check to reactor modules to ensure _initialize is only
 called once (#388)

Calling _initialize multiple times is undefined behavior, since the
ctors are not guaranteed to be idempotent. We should have this safety
check which is similar to #329.
---
 libc-bottom-half/crt/crt1-reactor.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/libc-bottom-half/crt/crt1-reactor.c b/libc-bottom-half/crt/crt1-reactor.c
index f507c9e..ea4a84f 100644
--- a/libc-bottom-half/crt/crt1-reactor.c
+++ b/libc-bottom-half/crt/crt1-reactor.c
@@ -1,7 +1,27 @@
+#if defined(_REENTRANT)
+#include <stdatomic.h>
+extern void __wasi_init_tp(void);
+#endif
 extern void __wasm_call_ctors(void);
 
 __attribute__((export_name("_initialize")))
 void _initialize(void) {
+#if defined(_REENTRANT)
+    static volatile atomic_int initialized = 0;
+    int expected = 0;
+    if (!atomic_compare_exchange_strong(&initialized, &expected, 1)) {
+        __builtin_trap();
+    }
+
+    __wasi_init_tp();
+#else
+    static volatile int initialized = 0;
+    if (initialized != 0) {
+        __builtin_trap();
+    }
+    initialized = 1;
+#endif
+
     // The linker synthesizes this to call constructors.
     __wasm_call_ctors();
 }