x86 汇编代码未编译

Question

我有以下代码，其中我试图在 C 中调用一个汇编函数，它试图在（QEmu 的）VGA 显示器上打印 "e"：

void main()
{
 extern void put_in_mem();
 char c = 'e';
 put_in_mem(c, 0xA0);
}

函数put_in_mem定义如下：

.global _put_in_mem
_put_in_mem:
push bp
mov bp, sp
mov cx, [bp + 4]
mov ax, [bp + 6]
mov ax, 0xb800
mov ds, ax
mov [bx], cx
add bx, 0x1
mov cx, 0x7  
mov [bx], cx
pop bp
ret

当我使用 nasm 编译上述汇编代码时，出现以下错误：

put_in_mem.asm:1: error: attempt to define a local label before any    non-local labels
put_in_mem.asm:1: error: parser: instruction expected

为什么会出现这个错误？

Answer 1

NASM gives special treatment to symbols beginning with a period. A label beginning with a single period is treated as a local label

NASM does have a global directive，但是写的没有句首。所以也许你打算写 global _put_in_mem

x86 汇编代码未编译

x86 assembly code not compiling

assembly

x86

nasm