How to resolve: warning: not protecting local variables: variable length buffer

when building my project, the following warning is generated:

warning: not protecting lo开发者_运维百科cal variables: variable length buffer

i have enabled the stack protector and already specified the size however this is still occurring.

-fstack-protector-all -Wall -Wstack-protector --param ssp-buffer-size=2

can you suggest a way to resolve the warning without actually turning off the warning flags? thanks