From 55b5481e7cb0492aed18d4e4cfb2e60ea83b07da Mon Sep 17 00:00:00 2001
From: Thibault Charbonnier <thibaultcha@me.com>
Date: Sun, 5 May 2024 15:24:36 -0700
Subject: [PATCH] fix(lib) prevent a segfault loading an empty .wat module with
 V8

Fixing it at the ngx-wasm-rs level produces a more descriptive error
message than doing it at the C level.

Fix #543
---
 lib/ngx-wasm-rs/lib/wat/src/lib.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/ngx-wasm-rs/lib/wat/src/lib.rs b/lib/ngx-wasm-rs/lib/wat/src/lib.rs
index 077ef0bd3..4ac81cacd 100644
--- a/lib/ngx-wasm-rs/lib/wat/src/lib.rs
+++ b/lib/ngx-wasm-rs/lib/wat/src/lib.rs
@@ -39,9 +39,13 @@ pub unsafe extern "C" fn ngx_wasm_wat_to_wasm(
     wat: *const wasm_byte_vec_t,
     wasm: *mut wasm_byte_vec_t,
 ) -> Option<Box<wasm_byte_vec_t>> {
-    let wat_slice;
+    let empty = Vec::new();
+    let mut wat_slice = empty.as_ref();
+
     unsafe {
-        wat_slice = std::slice::from_raw_parts((*wat).data, (*wat).size);
+        if (*wat).size > 0 {
+            wat_slice = std::slice::from_raw_parts((*wat).data, (*wat).size);
+        }
     }
 
     match wabt::wat2wasm(wat_slice) {