CODEWITHSUNDEEP
chashtablevalgrind
user2857096
user2857096

Reputation: 33

"Bad permissions for mapped region at address" Valgrind error for a hash table

I'm pretty new to C. When I run the following code for a hash table under Valgrind:

table *insertObject (table *h, int pref, char ch)
{
    struct node x;
    int i;
    if (ch < 0)
    {
        ch=256-ch;
    }
    x.chr=ch;
    x.pref=pref;
    i = hash(pref, ch, h->size);
    while (h->hash[i].pref!=0)
    {
        i++;
    }
    h->hash[i]=x;
    h->size++;
    return h;
}

I get the following error:

==9243== 
==9243== Process terminating with default action of signal 11 (SIGSEGV)
==9243==  Bad permissions for mapped region at address 0x6018A4
==9243==    at 0x4009CD: insertObject (encode.c:119)
==9243==    by 0x4008E3: main (encode.c:55)

Line 119 is the line

 h->hash[i]=x;

The funny thing is, when I run the whole code through a debugger, it works fine 90% of the time. However, for some special cases, the code segfaults, and the debugger tells me this is also the culprit. What's wrong?

Upvotes: 2

Views: 11498

Answers (1)

Giuseppe Pes
Giuseppe Pes

Reputation: 7912

The error is due to an incorrect memory access, basically your application is trying to access a memory area which is not mapped in its memory space.

Quite likely the value of i exceeds the limits of the hash array. I cannot be more precise because I do not how the hash function works and what perf stands for. However, you should verify the value of i with a debugger, in the 10% of case where the application does not work.

P.S. a program should work fine 100% of time.

Upvotes: 1

Related Questions