[英]How to use mmap like malloc?
I'm trying to allocate memory for 10x of my list struct then use it for my linked list but I keep getting a segmentation fault.我正在尝试为我的列表结构的 10x 分配内存,然后将它用于我的链表,但我不断收到分段错误。
Valgrind瓦尔格林德
==3806== Invalid write of size 4
==3806== at 0x4005FD: main (comp.c:14)
==3806== Address 0xffffffffffffffff is not stack'd, malloc'd or (recently) free'd
Sample Code示例代码
#include <sys/mman.h>
typedef struct list {
int num;
struct list *next;
}list;
int main()
{
list *nodes = mmap(NULL, sizeof(list) * 10, PROT_READ | PROT_WRITE, MAP_PRIVATE, -1, 0);
nodes[0].num = 1;
nodes[0].next = NULL;
}
The 0xffffffffffffffff
almost surely means that mmap
failed. 0xffffffffffffffff
几乎肯定意味着mmap
失败。 If you want to use it to allocate memory like malloc
, you have to do error checking just as you would for malloc
, except that you need to test the returned value against MAP_FAILED
instead of NULL
.如果你想用它来像分配内存malloc
,你所要做的错误检查就像你的malloc
,除非你需要测试对返回的值MAP_FAILED
而不是NULL
。
The failure is probably because you are trying to map a nonexistent file descriptor -1
.失败可能是因为您试图映射不存在的文件描述符-1
。 This is only allowed when the MAP_ANONYMOUS
flag is specified, which you did not include.这仅在指定了MAP_ANONYMOUS
标志时才允许,您未包括该标志。
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