From 98ae83daae67e9e7663b8345eced1de8c667271f Mon Sep 17 00:00:00 2001
From: Dan Gohman <dev@sunfishcode.online>
Date: Thu, 8 Dec 2022 10:35:46 -0800
Subject: [PATCH] Mangle "main" as "__main_void" on wasm32-wasi

On wasm, the age-old C trick of having a main function which can either have
no arguments or argc+argv doesn't work, because wasm requires caller and
callee signatures to match. WASI's current strategy is to have compilers
mangle main's name to indicate which signature they're using. Rust uses the
no-argument form, which should be mangled as `__main_void`.

This is needed on wasm32-wasi as of #105395.
---
 compiler/rustc_target/src/spec/wasm32_wasi.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/compiler/rustc_target/src/spec/wasm32_wasi.rs b/compiler/rustc_target/src/spec/wasm32_wasi.rs
index 6f0bbf0672d4..a0476d542e64 100644
--- a/compiler/rustc_target/src/spec/wasm32_wasi.rs
+++ b/compiler/rustc_target/src/spec/wasm32_wasi.rs
@@ -104,6 +104,10 @@ pub fn target() -> Target {
     // `args::args()` makes the WASI API calls itself.
     options.main_needs_argc_argv = false;
 
+    // And, WASI mangles the name of "main" to distinguish between different
+    // signatures.
+    options.entry_name = "__main_void".into();
+
     Target {
         llvm_target: "wasm32-wasi".into(),
         pointer_width: 32,
-- 
2.38.1