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main.c

@@ -0,0 +1,8 @@
+#include "headers/nstdo.h"
+extern long sys_write(int fd, const void *buf, size_t count);
+
+int main(void) {
+    const char msg[] = "Hello, World!\n";
+    sys_write(1, msg, sizeof(msg)-1);
+    return 0;
+}

nstdo.h

@@ -0,0 +1,52 @@
+#ifndef MINI_STDIO_H
+#define MINI_STDIO_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef unsigned long size_t;
+typedef long off_t;
+
+#define O_RDONLY 0
+#define O_WRONLY 1
+#define O_RDWR 2
+#define O_CREAT 64
+#define O_TRUNC 512
+#define O_APPEND 1024
+#define O_CLOEXEC 02000000
+
+typedef __builtin_va_list va_list;
+#define va_start(ap,last) __builtin_va_start(ap,last)
+#define va_arg(ap,type) __builtin_va_arg(ap,type)
+#define va_end(ap) __builtin_va_end(ap)
+
+#define SYS_READ 0
+#define SYS_WRITE 1
+#define SYS_OPEN 2
+#define SYS_CLOSE 3
+#define SYS_LSEEK 8
+
+static inline long _syscall3(long nr,long a1,long a2,long a3){long ret;asm volatile("syscall":"=a"(ret):"a"(nr),"D"(a1),"S"(a2),"d"(a3):"rcx","r11","memory");return ret;}
+
+#ifndef MY_BUFSIZ
+#define MY_BUFSIZ 4096
+#endif
+
+typedef struct{int fd;char buf[MY_BUFSIZ];size_t pos;size_t len;int mode;}MY_FILE;
+
+MY_FILE* my_fopen(const char* path,int flags,int mode);
+int my_fclose(MY_FILE* f);
+size_t my_fread(void* ptr,size_t size,size_t nmemb,MY_FILE* f);
+size_t my_fwrite(const void* ptr,size_t size,size_t nmemb,MY_FILE* f);
+int my_putc(int c,MY_FILE* f);
+int my_puts(const char* s,MY_FILE* f);
+off_t my_seek(MY_FILE* f,off_t offset,int whence);
+int my_printf(MY_FILE* f,const char* fmt,...);
+int my_vprintf(MY_FILE* f,const char* fmt,va_list ap);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

syscalls.asm

@@ -0,0 +1,16 @@
+global _start
+global sys_write
+extern main
+
+section .text
+
+sys_write:
+    mov     rax, 1
+    syscall
+    ret
+
+_start:
+    call    main
+    mov     rdi, rax
+    mov     rax, 60
+    syscall