我已经使用分配代码mmap
,但由于分段错误而无法释放它。我已经做好了mprotect
- PROT_WRITE
使其可写,但我仍然无法释放它。我的代码:
1 #include <stdio.h>
2 #include <memory.h>
3 #include <stdlib.h>
4 #include <unistd.h>
5 #include <sys/mman.h>
6 #include <sys/types.h>
7 #include <fcntl.h>
8
9 int main()
10 {
11 void * allocation;
12 size_t size;
13 static int devZerofd = -1;
14
15 if ( devZerofd == -1 ) {
16 devZerofd = open("/dev/zero", O_RDWR);
17 if ( devZerofd < 0 )
18 perror("open() on /dev/zero failed");
19 }
20
21 allocation = (caddr_t) mmap(0, 5000, PROT_READ|PROT_NONE, MAP_PRIVATE, devZerofd, 0);
22
23 if ( allocation == (caddr_t)-1 )
24 fprintf(stderr, "mmap() failed ");
25
26 if ( mprotect((caddr_t)allocation, 5000, PROT_WRITE) < 0 )
27 fprintf(stderr, "mprotect failed");
28 else
29 printf("mprotect done: memory allocated at address %u\n",allocation);
30
31 strcpy(allocation,"Hello, how are you");
32 puts(allocation);
33
34 if ( mprotect((caddr_t)allocation, 5000, PROT_WRITE) < 0 )
35 fprintf(stderr, "mprotect failed");
36
37 free(allocation);
38
39 }
40
41
你需要使用munmap http://pubs.opengroup.org/onlinepubs/9699919799/functions/munmap.html为了那个原因。您不需要执行任何其他操作(更改保护位等)。但你应该检查返回码munmap
.
munmap(allocation, 5000);
free(3)
只能用于释放通过分配的内存malloc(3)
.
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