hello! is there a way to declare a char array of length that will be determined by a variable later?

i'm working on a syntax checker program for a programming language and i have to use strlen() to check the longest line of code in the program before i can declare the length of the char array.

i know that i can use string or other containers for this but the library my professor gave me accepts only char array. for now, i'm just declaring a char array of size 901 but i know this would not be acceptable.