I couldn\'t disable it even though by using -std=c89 flag. How can I disable it?
Variable-length arrays in C89?
GCC always supported variable length arrays AFAIK. Setting -std to C89 doesn't turn off GCC extensions ...
See also:
https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html
http://tigcc.ticalc.org/doc/gnuexts.html#SEC76
Finally,
http://tigcc.ticalc.org/doc/gnuexts.html
'-pedantic' and other options cause warnings for many GNU C extensions. You can prevent such warnings within one expression by writing
__extension__before the expression.__extension__has no effect aside from this.