Question

I am working on Linux. In which section of memory are the command line arguments stored (stack or heap)?

I tried to execute free(argv) and I got a segmentation fault. Why is that?

Answer 1

I tried to execute free(argv) and I got a segmentation fault. Why is that?

You can only free what you malloc/calloc (and possibly realloc later on). Trying to free something else invokes Undefined Behaviour. One (good) way UB manifests itself is by producing a segmentation fault; a (bad) way is to make the program appear to work as intended.

As to where they are … read section 5.1.2.2.1 of the C99 Standard — its unspecified.

the strings pointed to by the argv array shall
be modifiable by the program, and retain their last-stored values between program
startup and program termination.