为什么我的 fputc 调用继续导致分段错误？

Question

我正在尝试创建一个程序，该程序创建一个新文件并将现有文件的内容复制到其中。我能够打开读取原始文件的内容并将其写入内存，但是当将内存内容写入新文件时，会发生分段错误。

section .data
openFile:    db 'file1.txt', 0       ; Source file to open for reading
fileModeR:   db 'r', 0               ; File mode for reading
writeFile:   db 'file2.txt', 0       ; Destination file to open for writing
fileModeW:   db 'w', 0               ; File mode for writing

section .bss
fileHandleR  resd 1                  ; To store the file descriptor for reading
fileHandleW  resd 1                  ; To store the file descriptor for writing
buffer       resb 1                  ; Reserve buffer for one character

section .text
extern fopen, fgetc, fputc, fclose
global main

main:
    ; Open source file for reading
    push fileModeR                    ; Push read mode
    push openFile                     ; Push file name
    call fopen
    add esp, 8
    mov [fileHandleR], eax            ; Store the file handle
    test eax, eax                     ; Check for null
    jz exit_program                  ; Exit if fopen failed

    ; Open destination file for writing
    push fileModeW                    ; Push write mode
    push writeFile                    ; Push file name
    call fopen
    add esp, 8
    mov [fileHandleW], eax            ; Store the file handle
    test eax, eax                     ; Check for null
    jz close_source                  ; Close source file and exit if fopen failed

    ; Read from file1.txt and write to file2.txt
copy_loop:
    mov eax, [fileHandleR]            ; Load the file pointer into eax
    push eax                          ; Push the file pointer onto the stack
    call fgetc                        ; Read a character
    add esp, 4                        ; Clean up the stack after the call
    test eax, eax                     ; Test for EOF or error
    js close_files                    ; If sign flag is set, hit EOF or error

    mov ecx, eax                      ; Move the character into ecx to use later with fputc
    mov eax, [fileHandleW]            ; Move file handle for writing into eaxn
    push ecx                          ; Push the character to write
    push eax                          ; Push the file handle for writing
    call fputc                        ; Write the character
    add esp, 8                        ; Clean up the stack

    test eax, eax                     ; Test for fputc success
    js close_files                    ; If sign flag is set, an error occurred

    jmp copy_loop                     ; Repeat the loop

close_files:
    mov eax, [fileHandleW]            ; Get the file handle for writing
    push eax                          ; Push it to fclose
    call fclose                       ; Close file2.txt
    add esp, 4                        ; Clean up the stack

close_source:
    mov eax, [fileHandleR]            ; Get the file handle for reading
    push eax                          ; Push it to fclose
    call fclose                       ; Close file1.txt
    add esp, 4                        ; Clean up the stack

exit_program:
    ; Exit the program
    mov eax, 1                        ; syscall number for exit
    xor ebx, ebx                      ; return 0 status
    int 0x80                          ; call kernel

错误发生在调用 fputc 时，我相信分段错误发生在

fputc

调用期间，表明文件句柄（应该是

FILE*

指针）未被

 正确识别fputc

。我是装配新手，我不明白为什么要这样做。我已附上 gdb 的屏幕截图，我可以看到一切似乎都在正常工作，直到 fputc 例如包含正确值的 ecx 和包含文件处理程序的 eax

Answer 1

fputc

希望字符作为第一个参数，

FILE*

作为第二个参数。这意味着它们应该以相反的顺序推送（因为这就是堆栈的工作原理，最后一个首先被取出。

因此，您应该先按

EAX

，然后按

ECX

，以便按正确的顺序读取它们。