C 对操作系统内核中链接的未定义引用

我有个问题。我使用本教程制作简单的操作系统内核：

但是，如果我想链接boot.o和kernel.o文件，gcc编译器将返回以下错误：

boot.o: In function `start':
boot.asm:(.text+0x6): undefined reference to `kernel_main'
collect2.exe: error: ld returned 1 exit status.

文件来源：

boot.asm

；声明用于创建多引导头的常量。
MBALIGN eq 1从
collect2.exe
参考来看，您似乎正在Microsoft®Windows®上使用GCC（例如，与Cygwin一起使用）。这意味着您似乎正在使用的本机可执行格式在C标识符前加上下划线，以使它们与程序集标识符分开，这是大多数对象格式所做的，但不是现代Unix下广泛使用的ELF格式

如果将调用更改为
\u kernel\u main
，链接错误可能会消失

但请注意这一行，引自您的问题：

#error "This tutorial needs to be compiled with a ix86-elf compiler"

您违反了所使用教程的基本原则。我建议您为i386（32位）安装GNU/Linux或BSD虚拟机，并在其中运行教程。
显示为对象文件的文件是源文件，您不能链接源文件，您需要汇编汇编程序源文件并编译C源文件以创建对象文件。汇编程序源文件通常以
.s
结尾，而C源文件则以
.C
结尾。您需要返回并从头开始阅读完整的教程，或者最好找到C和汇编程序教程并阅读它们！回购协议上的示例只适用于
make run
：谢谢，我是在qemu中启动操作系统的：）
#if !defined(__cplusplus)
#include <stdbool.h> /* C doesn't have booleans by default. */
#endif
#include <stddef.h>
#include <stdint.h>

/* Check if the compiler thinks if we are targeting the wrong operating system. */
#if defined(__linux__)
#error "You are not using a cross-compiler, you will most certainly run into trouble"
#endif

/* This tutorial will only work for the 32-bit ix86 targets. */
#if !defined(__i386__)
#error "This tutorial needs to be compiled with a ix86-elf compiler"
#endif

/* Hardware text mode color constants. */
enum vga_color
{
    COLOR_BLACK = 0,
    COLOR_BLUE = 1,
    COLOR_GREEN = 2,
    COLOR_CYAN = 3,
    COLOR_RED = 4,
    COLOR_MAGENTA = 5,
    COLOR_BROWN = 6,
    COLOR_LIGHT_GREY = 7,
    COLOR_DARK_GREY = 8,
    COLOR_LIGHT_BLUE = 9,
    COLOR_LIGHT_GREEN = 10,
    COLOR_LIGHT_CYAN = 11,
    COLOR_LIGHT_RED = 12,
    COLOR_LIGHT_MAGENTA = 13,
    COLOR_LIGHT_BROWN = 14,
    COLOR_WHITE = 15,
};

uint8_t make_color(enum vga_color fg, enum vga_color bg)
{
    return fg | bg << 4;
}

uint16_t make_vgaentry(char c, uint8_t color)
{
    uint16_t c16 = c;
    uint16_t color16 = color;
    return c16 | color16 << 8;
}

size_t strlen(const char* str)
{
    size_t ret = 0;
    while ( str[ret] != 0 )
        ret++;
    return ret;
}

static const size_t VGA_WIDTH = 80;
static const size_t VGA_HEIGHT = 25;

size_t terminal_row;
size_t terminal_column;
uint8_t terminal_color;
uint16_t* terminal_buffer;

void terminal_initialize()
{
    terminal_row = 0;
    terminal_column = 0;
    terminal_color = make_color(COLOR_LIGHT_GREY, COLOR_BLACK);
    terminal_buffer = (uint16_t*) 0xB8000;
    for ( size_t y = 0; y < VGA_HEIGHT; y++ )
    {
        for ( size_t x = 0; x < VGA_WIDTH; x++ )
        {
            const size_t index = y * VGA_WIDTH + x;
            terminal_buffer[index] = make_vgaentry(' ', terminal_color);
        }
    }
}

void terminal_setcolor(uint8_t color)
{
    terminal_color = color;
}

void terminal_putentryat(char c, uint8_t color, size_t x, size_t y)
{
    const size_t index = y * VGA_WIDTH + x;
    terminal_buffer[index] = make_vgaentry(c, color);
}

void terminal_putchar(char c)
{
    terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
    if ( ++terminal_column == VGA_WIDTH )
    {
        terminal_column = 0;
        if ( ++terminal_row == VGA_HEIGHT )
        {
            terminal_row = 0;
        }
    }
}

void terminal_writestring(const char* data)
{
    size_t datalen = strlen(data);
    for ( size_t i = 0; i < datalen; i++ )
        terminal_putchar(data[i]);
}
void kernel_main()
{
    terminal_initialize();
    /* Since there is no support for newlines in terminal_putchar yet, \n will
       produce some VGA specific character instead. This is normal. */
    terminal_writestring("Hello\n");
}

#error "This tutorial needs to be compiled with a ix86-elf compiler"