[Solved] Segmentation fault (core dumped) in C (with GMP lib)

Question

From the little bit of code you have, the difference seems to be the scope of the variable a. What is the point of calling mpz_init(a) on a variable with only local scope (within your init() function)? After init() returns, a disappears. If you need it for anything else later, the variable a, and presumably some of the side effects from mpz_init(), won’t exist. If you want the side effects of mpz_init() to persist past the end of init(), it must take effect on some structure that also persists past the end of init(). In your first example, a is declared with global scope, so it persists for the entirety of your program.

Accepted Answer

From the little bit of code you have, the difference seems to be the scope of the variable a. What is the point of calling mpz_init(a) on a variable with only local scope (within your init() function)? After init() returns, a disappears. If you need it for anything else later, the variable a, and presumably some of the side effects from mpz_init(), won’t exist. If you want the side effects of mpz_init() to persist past the end of init(), it must take effect on some structure that also persists past the end of init(). In your first example, a is declared with global scope, so it persists for the entirety of your program.