I use private anonymous mmap to allocate memory in my code, but when I use
valgrind to check memory leak. I got following error. I don't think there is
any memory error in the code.Thanks for help!
the command:
valgrind --tool=memcheck ./a.out
the error:
==2309== Memcheck, a memory error detector
==2309== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==2309== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==2309== Command: ./a.out
==2309==
==2309== Invalid write of size 1
==2309== at 0x8048751: main (test.cpp:15)
==2309== Address 0xffffffff is not stack'd, malloc'd or (recently) free'd
==2309==
==2309==
==2309== Process terminating with default action of signal 11 (SIGSEGV)
==2309== Access not within mapped region at address 0xFFFFFFFF
==2309== at 0x8048751: main (test.cpp:15)
==2309== If you believe this happened as a result of a stack
==2309== overflow in your program's main thread (unlikely but
==2309== possible), you can try to increase the size of the
==2309== main thread stack using the --main-stacksize= flag.
==2309== The main thread stack size used in this run was 8388608.
==2309==
==2309== HEAP SUMMARY:
==2309== in use at exit: 1,264 bytes in 1 blocks
==2309== total heap usage: 2 allocs, 1 frees, 1,616 bytes allocated
==2309==
==2309== LEAK SUMMARY:
==2309== definitely lost: 0 bytes in 0 blocks
==2309== indirectly lost: 0 bytes in 0 blocks
==2309== possibly lost: 0 bytes in 0 blocks
==2309== still reachable: 1,264 bytes in 1 blocks
==2309== suppressed: 0 bytes in 0 blocks
==2309== Rerun with --leak-check=full to see details of leaked memory
==2309==
==2309== For counts of detected and suppressed errors, rerun with: -v
==2309== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 19 from 8)
the code:
#include <stdio.h>
#include <sys/mman.h>
#include <errno.h>
#include <string.h>
const size_t PAGE_SIZE = 1 << 12;
int main()
{
unsigned start = 0;
char* p =(char*)
mmap(&start,PAGE_SIZE,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0);
*p = 1;
munmap(p,PAGE_SIZE);
}
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