Andy Res Andy Res - 1 year ago 58
C Question

Counting number of times a char is in a string results in a segmentation fault (core dumped)

This is an example from a book that counts the number of times a character is in a string:

int count_x(char* p, char x){
int count=0;
return count;

I call it like this:

int n = count_x("hello", 'l');

But I end up with:

Segmentation fault (core dumped)

From what I read, this might be thrown when the program is trying to access a memory area that it is not supposed to do (correct me if I am wrong).

I stepped with the debugger, and it goes something like this:

p = "hello" // And for every cycle it decreases,
p = "ello"
p = "llo"
p = "lo"
p = "o"
p = ""

and to my surprise it does not stop there, but it continues to cycle, which I suppose might be the cause of segmentation fault?

The book says that a test like
is equivalent with
, and as I understand this should be sufficient for the loop to stop when the string is consumed. Again, please correct me if I am wrong, and what can I do to fix it?

Answer Source

should be


because p is a pointer and it will be holding address and you need to check for the \0 character which is got by dereferencing the pointer *p

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