pointer usage

NeoAnderson · 09-07-2005, 10:13 PM

I was writing a program which included a type char ** variable. When I finished using it I tried to delete it for later use with the following code:

for (i = 0; chr[i]; i++)
delete chr[i];

Then I ran the program in gdb debuger, after the lines above, I tried to print out the memory addresses of the variable with the indexes I had used, what I had were still real memory addresses like 0x804e038 and 0x804e058, and they contain some freaky contents like "0 \004\b". Shouldn't their addresses be 0x0 after the deletion? How can I delete them completely so that I can reuse the pointer without worrying about the previous values?

Matir · 09-07-2005, 10:21 PM

I'm not sure about the delete operator in c++, but I imagine it's very similar to the free() function in c. Free does not change the value of a pointer, it only marks the memory as available for reallocation. Generally, I see calls to free in the form of:

Code:

char *a=malloc(5);
free(a);
a=NULL;

freegianghu · 09-07-2005, 10:48 PM

Code:

for (i = 0; chr[i]; i++) {
  delete chr[i];
  chr[i] = NULL;
}

NeoAnderson · 09-08-2005, 12:51 AM

thank you, by adding chr[i] = NULL; it works. btw, why the addresses of chr[3] and chr[4] were not 0x0 but 0x11 and 0x31 before I used them?

freegianghu · 09-08-2005, 01:00 AM

Quote:

Originally posted by NeoAnderson
thank you, by adding chr[i] = NULL; it works. btw, why the addresses of chr[3] and chr[4] were not 0x0 but 0x11 and 0x31 before I used them?

malloc does not init allocated memory, have a look at calloc