printf("%f",x) ok, printf("%F",x) error too many arguments for format

Question

Why the compiler gives me the error "too many arguments for format" when I use the specifier F in CodeBlocks?

#include <stdio.h>

int main()
{
    float x = 3.14159;
    printf("%f\n", x);
    printf("%F\n", x);
    return 0;
}

The errors:

error: unknown conversion type character 'F' in format [-Werror=format=]

error: too many arguments for format [-Werror=format-extra-args]

Answer 1

Looks like some versions of GCC don't recognize %F, oddly enough. My gcc version 9.2.0 (tdm64-1) for windows with C11 standard, does not recognize it though it only issues those as warning messages not errors.

$ gcc main2.c -Wextra -Wall -pedantic -std=c11
main2.c: In function 'main':
main2.c:7:14: warning: unknown conversion type character 'F' in format [-Wformat=]
    7 |     printf("%F\n", x);
      |              ^
main2.c:7:12: warning: too many arguments for format [-Wformat-extra-args]
    7 |     printf("%F\n", x);
      |            ^~~~~~

Upon execution the value is not printed.

I'm guessing you might be using some mingW installation in a Windows system and your compiler must be treating warnings as errors, which is not a bad idea.

As @HolyBlackCat suggested, adding -D__USE_MINGW_ANSI_STDIO flag solves the issue.

This thread has the instructions on how to do it.

@RobertS supports Monica Cellio answer has a link with instructions on how to add it to CodeBlocks.

Alternatively, for a quick fix of the code you can use %G, or %E for scientific notation.

Answer 2

The F format specifier was first introduced in C99. Your compiler either seems to be compliant to C89/C90 or the std=c90/std=c89 compiler option is enabled.

If you configured compiler is gcc, you can use the gcc --version command to detect the version.

Else you should check the set compiler options for which standard the compiler uses. Take a look at here:

How to add compiler flags on codeblocks

Although for Ubuntu (I don´t know on what OS you are using CodeBlocks), but this answer gives you an visual overview of the set up for compiler options in CodeBlocks.