cc99

How to compile a C project in C99 mode?

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=c99 or -std=gnu99 to compile your code

What does it mean?

How to fix it?

Solution

  • You have done this:

    for (int i=0;i<10;i++) {

    And you need to change it to this:

    int i;
for (i=0;i<10;i++) {

    Or, as the error says,

    use option -std=c99 or -std=gnu99 to compile your code.

    Update copied from Ryan Fox's answer:

    gcc -std=c99 foo.c -o foo

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