In /usr/bin/c99-gcc line 18:
	    echo >&2 "`basename $0` called with non ISO C99 option $i"
                      ^-----------^ SC2006: Use $(...) notation instead of legacy backticked `...`.
                                ^-- SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	    echo >&2 "$(basename "$0") called with non ISO C99 option $i"


In /usr/bin/c99-gcc line 24:
exec gcc $extra_flag ${1+"$@"}
         ^---------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
exec gcc "$extra_flag" ${1+"$@"}

For more information:
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...