Show HN: Uprintf a universal stb-style printf implementation for C (no OS)

13 points by Forgret 13 hours ago

I've been frustrated by the lack of a truly portable, no-dependency printf for embedded and kernel development. Most solutions are either too bloated or missing key features. So I built Uprintf. It's a single-header library that gives you full printf (flags, width, precision, floats, even custom specifiers) from bare metal to desktop, with zero dependencies or #ifdef hell. Key features: · One header file, no dependencies, no dynamic allocation · Full standard support: %d, %x, %f, %.*s, etc. · Extensible with custom format handlers (add %T for your project) · Configurable: disable floats, set locale, etc. · MIT Licensed. GitHub: https://github.com/Ferki-git-creator/Uprintf I'd love your feedback and contributions!

s_gourichon 3 hours ago

Nice. Comprehensive unit tests are indeed welcome. Even a simple test code that tests all features, flags combinations, etc, and outputs a log. It will make easy for anyone to run it and compare the logs.

I had a bug:

    u_printf( my_output_cb, NULL, "%d" NL, -42 );
prints:

--42

I may have found an explanation. In u_parse_format(), case 'i': calls u_itoa( value, buffer, 10, false ); which outputs minus sign.

Then if ( number ) does if ( sign ) { output_cb( '-', ctx ); chars_written++; } which outputs another minus sign.

fjfaase 12 hours ago

Nice work. I always have understood that snprintf does not write a null character when the produced string is longer than the given size. The snprintf function also can be called with a null pointer to calculate the length of the produced string.

You could add a c file with some unittests.

  • wahern 4 hours ago

    > I always have understood that snprintf does not write a null character when the produced string is longer than the given size.

    snprintf always null-terminates when the buffer length is greater than 0 and there's no error. That is, if snprintf returns >= 0 and the buffer length is > 0, the output is null-terminated.

    This should be clear from your local snprintf(3) man page (e.g. https://man.openbsd.org/snprintf), but also see the C23 standard (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf) and POSIX (https://pubs.opengroup.org/onlinepubs/9799919799/).

  • Forgret 12 hours ago

    Thanks, I will make and add unit tests As you requested, I'm already starting to do it, but in the meantime, if you want, you can support the project with a star. :)