Question

我正在做C和汇编，我想我会编写一个简单的代码来确保我理解如何在汇编中使用malloc，我只想分配一个4号int数组并用1,2填充它，汇编中的3,4值，然后用C打印。

C档案：

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h>
#include <malloc.h>
extern void myproc(int *arr); 
void main() {
int *p;
myproc(p);//call the assembly function ,where i do p=malloc(sizeof(int)*4)
printf("%d %d %d %d ",p[0],p[1],p[2],p[3]);//supposed to print 1 2 3 4 but its not
} // main

装配文件：

.MODEL small
    .STACK 100H
    .DATA
    .CODE
    .386
    .387
    PUBLIC _myproc
    EXTRN _malloc:NEAR
    _myproc PROC NEAR
    ;This procedure is supposed to do  p=malloc(sizeof(int)*4) then p[0]=1 ,p[1]=2,p[2]=3,p[3]=4.
    PUSH BP
    MOV BP,SP
    XOR DX,DX
    PUSH BX
    MOV AX,4;prepare to pass the parameter for malloc
    SHL AX,1;multiply by 2 for int array
    PUSH AX;pass 4*2 to malloc
    CALL _malloc;calling malloc
    ADD SP,2
    MOV WORD PTR [BP+4],AX;set the pointer to the newly allocated array 
    MOV BX,WORD PTR [BP+4]
    ;do p[0]=1 ,p[1]=2,p[2]=3,p[3]=4
    MOV WORD PTR [BX],1
    ADD BX,2
    MOV WORD PTR [BX],2
    ADD BX,2
    MOV WORD PTR [BX],3
    ADD BX,2
    MOV WORD PTR [BX], 4
    POP BX
    POP BP
    RET;;when i get back to the C file to print the values it doesnt work ,its like i didn't set 1,2,3,4.
    _myproc ENDP

    END

Answer 1

将功能更改为extern void myproc(int **arr);，然后将其传递给&p。并将大会改为：

.MODEL small
    .STACK 100H
    .DATA
    .CODE
    .386
    .387
    PUBLIC _myproc
    EXTRN _malloc:NEAR
    _myproc PROC NEAR
    ;This procedure is supposed to do  p=malloc(sizeof(int)*4) then p[0]=1 ,p[1]=2,p[2]=3,p[3]=4.
    PUSH BP
    MOV BP,SP
    XOR DX,DX
    PUSH BX
    PUSH SI
    MOV AX,4;prepare to pass the parameter for malloc
    SHL AX,1;multiply by 2 for int array
    PUSH AX;pass 4*2 to malloc
    CALL _malloc;calling malloc
    ADD SP,2
    MOV SI,WORD PTR [BP+4];get the pointer adress
    MOV [SI],AX;set the point to point on the newly allocated array
    ;do p[0]=1 ,p[1]=2,p[2]=3,p[3]=4
    MOV BX,[SI]
    MOV WORD PTR [BX],1
    ADD BX,2
    MOV WORD PTR [BX],2
    ADD BX,2
    MOV WORD PTR [BX],3
    ADD BX,2
    MOV WORD PTR [BX], 4
    POP SI
    POP BX
    POP BP
    RET;;when i get back to the C file to print the values it doesnt work ,its like i didn't set 1,2,3,4.
    _myproc ENDP

    END

修复它

组装8086中的malloc如何工作？

1 个答案: