How to compile a C project in C99 mode?

Question

I got the following error message while compiling the C code:

error: \'for\' loop initial declarations are only allowed in C99 mode
note: use option -std=c9         


        

Answer 1

The other answers give you a work around to deal with GCC's default mode. If you'd like to use C99, (which I do recommend in general) then you have to add that compiler flag:

gcc -std=c99 foo.c -o foo

Or, if you're using a standard makefile, add it to the CFLAGS variable.