From 6e6ee64bb4cf10a98c7bd92e06090502eb67e402 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Tue, 17 Feb 2026 21:54:18 +0100
Subject: initial commit

---
 .gitignore          |  1 +
 .vscode/launch.json | 23 ++++++++++++++
 CMakeLists.txt      | 19 ++++++++++++
 CMakePresets.json   | 21 +++++++++++++
 src/SDL_interface.S | 26 ++++++++++++++++
 src/main.S          | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 178 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 .vscode/launch.json
 create mode 100644 CMakeLists.txt
 create mode 100644 CMakePresets.json
 create mode 100644 src/SDL_interface.S
 create mode 100644 src/main.S

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..567609b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+build/
diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 0000000..b148580
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,23 @@
+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Debug",
+            "type": "cppdbg",
+            "request": "launch",
+            "program": "${command:cmake.launchTargetPath}",
+            "args": [],
+            "stopAtEntry": false,
+            "cwd": "${workspaceFolder}",
+            "environment": [],
+            "MIMode": "gdb",
+            "setupCommands": [
+                {
+                    "description": "Enable pretty-printing for gdb",
+                    "text": "-enable-pretty-printing",
+                    "ignoreFailures": true
+                }
+            ]
+        }
+    ]
+}
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..90d304a
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,19 @@
+cmake_minimum_required(VERSION "4.2.0")
+
+project("snake.s"
+  DESCRIPTION "The assembly snake!"
+  VERSION "1.0.0"
+  LANGUAGES ASM
+)
+
+find_package("SDL2" REQUIRED)
+
+add_executable("snake.s"
+  "src/main.S"
+)
+
+target_link_libraries("snake.s" PRIVATE
+  "SDL2::SDL2"
+)
+
+install(TARGETS "snake.s")
diff --git a/CMakePresets.json b/CMakePresets.json
new file mode 100644
index 0000000..dc09fc2
--- /dev/null
+++ b/CMakePresets.json
@@ -0,0 +1,21 @@
+{
+  "version": 10,
+  "configurePresets": [
+    {
+      "name": "default",
+      "displayName": "Default Configuration",
+      "generator": "Ninja",
+      "binaryDir": "${sourceDir}/build",
+      "cacheVariables": {
+        "CMAKE_BUILD_TYPE": "Debug"
+      }
+    }
+  ],
+  "buildPresets": [
+    {
+      "name": "default",
+      "displayName": "Default Build",
+      "configurePreset": "default"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/src/SDL_interface.S b/src/SDL_interface.S
new file mode 100644
index 0000000..02302b4
--- /dev/null
+++ b/src/SDL_interface.S
@@ -0,0 +1,26 @@
+#define SDL_INIT_TIMER           0x00000001u
+#define SDL_INIT_AUDIO           0x00000010u
+#define SDL_INIT_VIDEO           0x00000020u
+#define SDL_INIT_JOYSTICK        0x00000200u
+#define SDL_INIT_HAPTIC          0x00001000u
+#define SDL_INIT_GAMECONTROLLER  0x00002000u
+
+#define SDL_WINDOW_SHOWN         0x00000004u
+
+#define SDL_WINDOWPOS_UNDEFINED  0x1FFF0000u
+
+// int SDL_Init(uint32_t flags)
+.type SDL_Init, @function
+.extern SDL_Init
+
+// SDL_Window * SDL_CreateWindow(const char *title, int x, int y, int w, int h, uint32_t flags)
+.type SDL_CreateWindow, @function
+.extern SDL_CreateWindow
+
+// void SDL_DestroyWindow(SDL_Window *window)
+.type SDL_DestroyWindow, @function
+.extern SDL_DestroyWindow
+
+// void SDL_Quit(void)
+.type SDL_Quit, @function
+.extern SDL_Quit
\ No newline at end of file
diff --git a/src/main.S b/src/main.S
new file mode 100644
index 0000000..0a21f83
--- /dev/null
+++ b/src/main.S
@@ -0,0 +1,88 @@
+#include "SDL_interface.S"
+
+#define SCREEN_WIDTH 800
+#define SCREEN_HEIGHT 600
+
+// integer-params:  RDI, RSI, RDX, RCX, R8, R9
+// caller-saved:    RAX, RCX, RDX, RSI, RDI, R8-R11
+// callee-saved:    RBX, RSP, RBP, R12-R15
+
+.section .rodata
+  failed_to_create_window:  .string "Window could not be created\nSDL_error: %s\n"
+  failed_to_initialize_sdl: .string "SDL could not be initialized\nSDL_error: %s\n"
+  greeting:                 .string "Hello, SDL!\n"
+  window_title:             .string "snake.s"
+
+.section .text
+  .global main
+
+  // void _print_sdl_error(char const * format)
+  .type _print_sdl_error, @function
+  _print_sdl_error:
+    push %rbp
+    mov %rsp, %rbp
+
+    push %rdi
+    sub $8, %rsp
+ 
+    call SDL_GetError@PLT
+    mov %rax, %rsi
+ 
+    add $8, %rsp
+    pop %rdi
+
+    call printf@PLT
+    jmp .Lexit
+
+    leave
+    ret
+
+  .type main, @function
+  main: 
+    push %rbp
+    mov %rsp, %rbp
+
+    // initialize SDL
+    mov $SDL_INIT_VIDEO, %rdi
+    call SDL_Init@PLT
+
+    // check if initialization was successful
+    cmp $0, %rax
+    jae 1f
+      lea failed_to_initialize_sdl(%rip), %rdi
+      call _print_sdl_error@PLT
+      mov $1, %rax
+      jmp .Lexit
+  1:
+
+    // create a window
+    lea window_title(%rip), %rdi
+    mov $SDL_WINDOWPOS_UNDEFINED, %rsi
+    mov $SDL_WINDOWPOS_UNDEFINED, %rdx
+    mov $SCREEN_WIDTH, %rcx
+    mov $SCREEN_HEIGHT, %r8
+    mov $SDL_WINDOW_SHOWN, %r9
+    call SDL_CreateWindow@PLT
+
+    cmp $0, %rax
+    jne 1f
+      lea failed_to_create_window(%rip), %rdi
+      call _print_sdl_error@PLT
+      mov $1, %rax
+      jmp .Lexit
+  1:
+
+  mov %rax, %rdi
+  call SDL_DestroyWindow@PLT
+  call SDL_Quit@PLT
+
+  .Lsuccess:
+    lea greeting(%rip), %rdi
+    xor %rax, %rax
+    call printf@PLT
+
+    xor %rax, %rax
+
+  .Lexit:
+    leave
+    ret
-- 
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