Safe printf implementation for the C language: safe_printf()

1. Why do we need safe_printf()?

• When using printf() in the C language, using an incorrect format specifier can lead to unexpected behavior or program crashes.
• For example, printf("%s", l1); If you try to output a long-type variable to %s, you may get a runtime error.

2. Implement safe_printf() that works in GCC, Clang, and MSVC (Microsoft Visual C++)

• Here's an implementation of safe_printf() that enables formatting in GCC and Clang, and works fine in MSVC.

#include "safe_printf.h" // include header 

int main()
{
    long l1 = 10;

    safe_printf( "%ld\n", l1 );  // ✅ Correct usage
 // safe_printf(  "%s\n", l1 );  // ❌ A Compile Warning occurs. (format mismatch)

    return 0;
}

3. Key Improvements

• Detecting formatting errors in GCC/Clang
  • __attribute__((format(printf, x, y))) If there is incorrect formatting, a warning is raised at compile time.
  • For example, safe_printf("%s", l1); Alert output.
• Can run securely even on MSVC
  • MSVC does not support __attribute__, so the compiler cannot detect errors, but it is configured to work without errors when executed.
• Processing _snprintf compatible with snprintf
  • MSVC uses _snprintf by default instead of snprintf, so it can be automatically mapped and run safely in a Windows environment.

4. Summary

• I have now implemented safe_printf(), which is available in GCC, Clang, and MSVC.
  • If you use GCC/Clang, invalid formatters can be detected at compile time.
  • Even on MSVC, safe_printf() can run without problems.
  • In Windows/Linux/macOS environments, you can provide safe output with the same code.
• Now you can write more secure C code without worrying about formatting errors when using printf()! 🚀

4.1. Compiler

• gcc
• clang
• Visual C++

4.2. License

• MIT License
• https://github.com/JayTwoLab/safe_printf