c++ - 出现无法分配内存错误

Question

我的程序中出现此错误...

mprotect: Cannot allocate memory 

ulimit -a 给出输出:

core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 20
file size               (blocks, -f) unlimited
pending signals                 (-i) 16382
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) unlimited
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

我试图保护的内存量是 60 MB。有人可以告诉我问题是什么以及如何解决吗？

Answer 1

Return Value

On success, mprotect() returns zero.
On error, -1 is returned, and errno is set appropriately.

Errors

EACCES
The memory cannot be given the specified access. This can happen, for example, if
you mmap(2) a file to which you have read-only access, then ask mprotect() to
mark it PROT_WRITE.

EFAULT
The memory cannot be accessed.

EINVAL
addr is not a valid pointer, or not a multiple of PAGESIZE.

ENOMEM
Internal kernel structures could not be allocated.
Or: addresses in the range [addr, addr+len] are invalid for the address space of
the process, or specify one or more pages that are not mapped.

根据错误消息，您可能遇到 ENOMEM 错误，并且查看错误代码，这并不一定意味着无法分配内存。您的地址范围可能无效，或者(很可能)您有未映射的页面。

不要试图一次性保护这么大的内存。考虑到虚拟内存的工作原理，该大块中的某些页面不会被映射的可能性太高了。您需要确保在调用 mprotect 之前映射有问题的页面。

当您使用系统函数时，阅读该函数的手册页总是一个好主意。然后再读一遍。手册页有时可能有点简洁。