Getting the warning " ISO C90 forbids variable-size array" in gcc compiler while compiling C90 code

Question

I am compiling my C90 c code in gcc . I am getting the warningISO C90 forbids variable-size array while making the declaration like

int symbols[nc];

Where nc is integer whose value is read from the input file. The values on the input files are varied so i can't keep a constant value. How can I get rid of it? Is it indeed necessary to resolve this warning or we can simply ignore it?

Thanks in advance.

Answer 1

You get that warning because C90 does not support variable length arrays.

You'll either have to switch gcc to C99 mode (which does support vla) , by using the -std=c99 or std=gnu99 command line flag, or rewrite your code to dynamically allocate memory or use a fixed size array.

The warning just tells you that you're not conforming to C90 in this case, but it's otherwise safe. Ignoring a warning should really not be an option though.