From 3ba0beee9610d2e173a2420bfa97afde09e4c567 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Tue, 9 Sep 2025 13:41:26 +0200
Subject: [PATCH] Support for SysV for CVaList

---
 lib/std/core/cinterop.c3 | 47 +++++++++++++++++++++++++++++++++++++++-
 releasenotes.md          |  2 +-
 2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/lib/std/core/cinterop.c3 b/lib/std/core/cinterop.c3
index d8a53b8bd..bc3f9073b 100644
--- a/lib/std/core/cinterop.c3
+++ b/lib/std/core/cinterop.c3
@@ -2,6 +2,8 @@
 // Use of this source code is governed by the MIT license
 // a copy of which can be found in the LICENSE_STDLIB file.
 module std::core::cinterop;
+import std::core::env;
+
 
 const C_INT_SIZE = $$C_INT_SIZE;
 const C_LONG_SIZE = $$C_LONG_SIZE;
@@ -60,7 +62,8 @@ macro typeid unsigned_int_from_bitsize(usz $bitsize) @private
 	$endswitch
 }
 
-module std::core::cinterop @if(env::DARWIN && env::AARCH64);
+const USE_STACK_VALIST = env::ARCH_32_BIT || env::WIN32 || (env::DARWIN && env::AARCH64);
+module std::core::cinterop @if(USE_STACK_VALIST);
 
 typedef CVaList = void*;
 macro CVaList.next(&self, $Type)
@@ -70,3 +73,45 @@ macro CVaList.next(&self, $Type)
 	return *($Type*)ptr;
 }
 
+module std::core::cinterop @if(env::X86_64 && !env::WIN32);
+
+struct CVaListData
+{
+    uint gp_offset;
+    uint fp_offset;
+    void *overflow_arg_area;
+    void *reg_save_area;
+}
+
+typedef CVaList = CVaListData*;
+
+macro CVaList.next(self, $Type)
+{
+	CVaListData* data = (CVaListData*)self;
+	$switch:
+	    $case $Type.kindof == FLOAT ||| ($Type.kindof == VECTOR && $Type.sizeof <= 16):
+	        var $LoadType = $Type.sizeof < 8 ? double : $Type;
+	        if (data.fp_offset < 6 * 8 + 8 * 16 )
+			{
+				defer data.fp_offset += (uint)mem::aligned_offset($Type.sizeof, 16);
+				return ($Type)*($LoadType*)(data.reg_save_area + data.fp_offset);
+			}
+			void* ptr = mem::aligned_pointer(data.overflow_arg_area, max(8, $Type.alignof));
+			defer data.overflow_arg_area = ptr + $Type.sizeof;
+			return ($Type)*($LoadType*)ptr;
+		$case $Type.kindof == SIGNED_INT || $Type.kindof == UNSIGNED_INT:
+	        var $LoadType = $Type.sizeof < 4 ? int : $Type;
+			if (data.gp_offset < 6 * 8 && $Type.sizeof <= 8)
+			{
+				defer data.gp_offset += (uint)mem::aligned_offset($Type.sizeof, 8);
+				return ($Type)*($LoadType*)(data.reg_save_area + data.gp_offset);
+			}
+			void* ptr = mem::aligned_pointer(data.overflow_arg_area, max(8, $Type.alignof));
+			defer data.overflow_arg_area = ptr + $Type.sizeof;
+			return ($Type)*($LoadType*)ptr;
+		$default:
+			void* ptr = mem::aligned_pointer(data.overflow_arg_area, max(8, $Type.alignof));
+			defer data.overflow_arg_area = ptr + $Type.sizeof;
+			return *($Type*)ptr;
+	$endswitch
+}
\ No newline at end of file
diff --git a/releasenotes.md b/releasenotes.md
index fb39ed3e4..b6d575d7e 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -26,7 +26,7 @@
   `path::public_share_directory`, `path::templates_directory`, `path::saved_games_directory`, `path::music_directory`, `path::downloads_directory`.
 - Add `LinkedList` array_view to support `[]` and `foreach`/`foreach_r`. #2438
 - Make `LinkedList` printable and add `==` operator. #2438
-- CVaList support on MacOS aarch64.
+- CVaList support on MacOS aarch64, SysV ABI x64.
 
 ## 0.7.5 Change list