Question

I’m defining a char pointer in this manner.

char *s=(char *)malloc(10);

After I fill in all possible values that can fit here, I want to clear whatever I wrote to s and without using malloc again want to write in s? How can I do this?

I need to update the contents but if in the last iteration not all values are updated, then I’ll be processing over old values which I do not want to do.

Answer 1

Be careful!

malloc(sizeof(2*5)) is the same as malloc(sizeof(int)) and allocates just 4 bytes on a 32 bit system. If you want to allocate 10 bytes use malloc(2 * 5).

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You can clear the memory allocated by malloc() with memset(s, 0, 10) or memset(s, 0, sizeof(int)), just in case this was really what you intended.

See man memset.

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Another way to clear the memory is using calloc instead of malloc. This allocates the memory as malloc does, but sets the memory to zero as well.