From 27857866c8cd7723ba7c8c5b0f921a0e97bd8fbf Mon Sep 17 00:00:00 2001
From: William Venner <william@venner.io>
Date: Mon, 20 Sep 2021 20:07:46 +0100
Subject: [PATCH] Add macro to define a function and type alias with fake
 calling convention attributes per platform

---
 gmod/src/hax.rs | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/gmod/src/hax.rs b/gmod/src/hax.rs
index 0a9078b..d319fa5 100644
--- a/gmod/src/hax.rs
+++ b/gmod/src/hax.rs
@@ -22,6 +22,60 @@ macro_rules! __vtable_offset {
 	};
 }
 
+#[macro_export]
+/// Common pattern for detouring.
+/// # Example
+/// ```norun
+/// __callingconv_func! {
+///     #[win32 = "stdcall"]
+///     #[win64 = "stdcall"]
+///     #[linux32 = "C"]
+///     #[linux64 = "C"]
+/// 	CVoiceGameMgrHelper_CanPlayerHearPlayer = extern fn(listener: *mut c_void, talker: *mut c_void) -> bool {
+/// 	    println!("listener {:?} talker {:?}", listener, talker);
+/// 	    false
+///     }
+/// }
+/// ```
+macro_rules! __callingconv_func {
+	{ @callingconv $ty:ident = extern $callingconv:tt fn($($ident:ident: $arg:ty),*) $(-> $rtn:ty)? $code:block } => {
+		type $ty = extern $callingconv fn($($ident: $arg),*) $(-> $rtn)?;
+		extern $callingconv fn $ty($($ident: $arg),*) $(-> $rtn)? $code
+	};
+
+	{ @callingconv $ty:ident = extern $callingconv:tt fn($($ident:ident: $arg:ty),*) $(-> $rtn:ty)? } => {
+		type $ty = extern $callingconv fn($($ident: $arg),*) $(-> $rtn)?;
+	};
+
+	{ #[win32 = $win32:tt] #[win64 = $win64:tt] #[linux32 = $linux32:tt] #[linux64 = $linux64:tt] $ty:ident = extern fn($($ident:ident: $arg:ty),*) $(-> $rtn:ty)? $code:block } => {
+		#[cfg(all(target_os = "windows", target_pointer_width = "32"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $win32 fn($($ident: $arg),*) $(-> $rtn)? $code }
+
+		#[cfg(all(target_os = "windows", target_pointer_width = "64"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $win64 fn($($ident: $arg),*) $(-> $rtn)? $code }
+
+		#[cfg(all(target_os = "linux", target_pointer_width = "32"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $linux32 fn($($ident: $arg),*) $(-> $rtn)? $code }
+
+		#[cfg(all(target_os = "linux", target_pointer_width = "64"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $linux64 fn($($ident: $arg),*) $(-> $rtn)? $code }
+	};
+
+	{ #[win32 = $win32:tt] #[win64 = $win64:tt] #[linux32 = $linux32:tt] #[linux64 = $linux64:tt] $ty:ident = extern fn($($ident:ident: $arg:ty),*) $(-> $rtn:ty)? } => {
+		#[cfg(all(target_os = "windows", target_pointer_width = "32"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $win32 fn($($ident: $arg),*) $(-> $rtn)? }
+
+		#[cfg(all(target_os = "windows", target_pointer_width = "64"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $win64 fn($($ident: $arg),*) $(-> $rtn)? }
+
+		#[cfg(all(target_os = "linux", target_pointer_width = "32"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $linux32 fn($($ident: $arg),*) $(-> $rtn)? }
+
+		#[cfg(all(target_os = "linux", target_pointer_width = "64"))]
+		$crate::__callingconv_func! { @callingconv $ty = extern $linux64 fn($($ident: $arg),*) $(-> $rtn)? }
+	};
+}
+
 #[macro_export]
 /// Common pattern for detouring.
 macro_rules! __gmod_func {