Avoid gcc dependency

src/sys.rs

@@ -1,16 +1,22 @@
 #[link(name = "syscalls")]
 extern "C" {
+    #[link_name = "_start_window_draw"]
     pub fn start_window_draw();
 
+    #[link_name = "_end_window_draw"]
     pub fn end_window_draw();
 
-    #[link_name = "exit0"]
+    #[link_name = "_exit"]
     pub fn exit() -> !;
 
+    #[link_name = "_define_window"]
     pub fn define_window(ebx: u32, ecx: u32, edx: u32, edi: u32);
+    #[link_name = "_display_message"]
     pub fn display_message(ebx: u32, ecx: u32, edx: u32, edi: u32, esi: u32);
 
+    #[link_name = "_wait_event"]
     pub fn wait_event() -> u32;
 
+    #[link_name = "_pressed_key"]
     pub fn pressed_key() -> u32;
 }

src/syscalls.S

@@ -0,0 +1,67 @@
+BITS 32
+
+section .text
+    global _exit
+    global _start_window_draw
+    global _end_window_draw
+    global _define_window
+    global _display_message
+    global _wait_event
+    global _pressed_key
+
+_exit:
+    mov eax, -1
+    int 0x40
+
+_start_window_draw:
+    mov eax, 0xc
+    mov ebx, 1
+    int 0x40
+    ret
+
+_end_window_draw:
+    mov eax, 0xc
+    mov ebx, 2
+    int 0x40
+    ret
+
+_define_window:
+    push edi
+    push ebx
+    xor eax, eax
+    mov ebx, dword [esp + 0x14]
+    mov ecx, dword [esp + 0x18]
+    mov edx, dword [esp + 0x1c]
+    mov edi, dword [esp + 0x20]
+    mov ebx, 2
+    int 0x40
+    pop ebx
+    pop edi
+    ret
+
+_display_message:
+    push edi
+    push esi
+    push ebx
+    mov eax, 4
+    mov ebx, dword [esp + 0x14]
+    mov ecx, dword [esp + 0x18]
+    mov edx, dword [esp + 0x1c]
+    mov esi, dword [esp + 0x20]
+    mov edi, dword [esp + 0x24]
+    mov ebx, 2
+    int 0x40
+    pop ebx
+    pop esi
+    pop edi
+    ret
+
+_wait_event:
+    mov eax, 0xa
+    int 0x40
+    ret
+
+_pressed_key:
+    mov eax, 2
+    int 0x40
+    ret

src/syscalls.c

@@ -1,54 +0,0 @@
-void start_window_draw() {
-    __asm__ volatile (
-        "int $0x40;"
-        :: "a"(12), "b"(1)
-    );
-}
-
-void end_window_draw() {
-    __asm__ volatile (
-        "int $0x40;"
-        :: "a"(12), "b"(2)
-    );
-}
-
-void exit0() {
-    __asm__ volatile (
-        "int $0x40;"
-        :: "a"(-1)
-    );
-}
-
-void define_window(unsigned ebx, unsigned ecx, unsigned edx, unsigned edi) {
-    __asm__ volatile (
-        "int $0x40;"
-        :: "a"(0), "b"(ebx), "c"(ecx), "d"(edx), "D"(edi)
-        : "memory"
-    );
-}
-
-void display_message(unsigned ebx, unsigned ecx, unsigned edx, unsigned edi, unsigned esi) {
-    __asm__ volatile (
-        "int $0x40;"
-        :: "a"(4), "b"(ebx), "c"(ecx), "d"(edx), "D"(edi), "S"(esi)
-        : "memory"
-    );
-}
-
-unsigned wait_event() {
-    unsigned res;
-    __asm__ volatile (
-        "int $0x40;"
-        : "=r"(res) : "a"(10)
-    );
-    return res;
-}
-
-unsigned pressed_key() {
-    unsigned res;
-    __asm__ volatile (
-        "int $0x40;"
-        : "=r"(res) : "a"(2)
-    );
-    return res;
-}