From 696efd25b5a7506ce061bd8c67b5abb3f39aa976 Mon Sep 17 00:00:00 2001
From: Cassie Jones <code@witchoflight.com>
Date: Sun, 1 Mar 2020 14:30:22 +0100
Subject: [PATCH] Modify runtime symbol decoration

C name decoration varies across platforms. On macOS, names from C are
prefixed with an underscore. On Linux, they're not, and on 64-bit
Windows they're not.

The macOS situation observed by inspecting the symbols.
Linux compatibility issue discovered here (and above in the thread):
https://twitter.com/16kbps/status/1233955883148861440
Windows symbol decoration documented here:
https://docs.microsoft.com/en-us/cpp/build/reference/decorated-names#FormatC
> Note that in a 64-bit environment, functions are not decorated.

Currently handling this with conditional compilation, but that prevents
cross-compilation. In the future it would be good to have the formatting
method select how to print them, but that would involve switching away
from fmt::Display, since we can't pass the ABI information into that.
Alternately, we could pack the ABI information into the symbol enum.
---
 src/trans/x64.rs | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/trans/x64.rs b/src/trans/x64.rs
index fbc7398..2608c79 100644
--- a/src/trans/x64.rs
+++ b/src/trans/x64.rs
@@ -7,6 +7,15 @@ use std::{
     io::{self, Write},
 };
 
+#[cfg(target_os = "macos")]
+macro_rules! extern_label {
+    ($l:literal) => { Label::Extern(concat!("_", $l)) }
+}
+#[cfg(not(target_os = "macos"))]
+macro_rules! extern_label {
+    ($l:literal) => { Label::Extern($l) }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum Label {
     Global(u32),
@@ -216,7 +225,7 @@ fn compile_func(func: &Func) -> Definition {
                 body.push(Inst::Lea(Reg::Rdi, Addr::Rip(Label::Function(*name))));
                 body.push(Inst::Imm(Reg::Rsi, *params as i64));
                 body.push(Inst::Imm(Reg::Rdx, upvars.len() as i64));
-                body.push(Inst::Call(Label::Extern("_ivy_make_lam")));
+                body.push(Inst::Call(extern_label!("ivy_make_lam")));
                 // @TODO: Implement copying in closure captures
                 assert!(upvars.is_empty());
                 body.push(Inst::Store(stack(ssa), Reg::Rax));
@@ -231,11 +240,11 @@ fn compile_func(func: &Func) -> Definition {
                     Some(s) => body.push(Inst::Load(Reg::Rsi, stack(s))),
                     None => body.push(Inst::Imm(Reg::Rsi, 0)),
                 }
-                body.push(Inst::Call(Label::Extern("_ivy_app")));
+                body.push(Inst::Call(extern_label!("ivy_app")));
                 while let Some(term) = terms.next() {
                     body.push(Inst::Mov(Reg::Rdi, Reg::Rax));
                     body.push(Inst::Load(Reg::Rsi, stack(term)));
-                    body.push(Inst::Call(Label::Extern("_ivy_app_mut")));
+                    body.push(Inst::Call(extern_label!("ivy_app_mut")));
                 }
                 body.push(Inst::Store(stack(ssa), Reg::Rax));
             }
@@ -345,7 +354,7 @@ fn builtin(name: &str) -> (u16, &'static str, &'static [Inst]) {
             "debug",
             &[
                 Inst::Load(Reg::Rdi, Addr::Off(Reg::Rdi, 0x18)),
-                Inst::Jmp(Label::Extern("_ivy_debug")),
+                Inst::Jmp(extern_label!("ivy_debug")),
             ],
         ),
         name => panic!("Unsupported builtin '{}' for x64", name),
-- 
2.47.0