Call to sprintf results in linkage errors on arm build

Hi All,

It seems like it is not possible to build on arm if your making a call to the C library function sprintf.
Sprintf is usually the "goto replacement" for itoa, so a bit of a shame it dosent work.

How to reproduce:
Create any project that makes a call to sprintf and try to build it.

(My exact case used %i in the format string to print an integer).

This is the linkage error that shows up:

usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-abort.o): in function abort': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/stdlib/../../../../../../../../newlib/libc/stdlib/abort.c:59: undefined reference to _exit'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-signalr.o): in function _kill_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/signalr.c:53: undefined reference to _kill'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-signalr.o): in function _getpid_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/signalr.c:83: undefined reference to _getpid'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-writer.o): in function _write_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/writer.c:49: undefined reference to _write'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-closer.o): in function _close_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/closer.c:47: undefined reference to _close'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-fstatr.o): in function _fstat_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/fstatr.c:55: undefined reference to _fstat'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-isattyr.o): in function _isatty_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/isattyr.c:52: undefined reference to _isatty'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-lseekr.o): in function _lseek_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/lseekr.c:49: undefined reference to _lseek'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-readr.o): in function _read_r': /build/newlib-CVVEyx/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/readr.c:49: undefined reference to _read'

Perhaps this was an intentional left out function, but there is no mentioning of it not being available in the documentation.

Kind regards,
/Jimmie

The problem is newlib sprintf() uses malloc() for certain conversions, which links it to a bunch of other OS-type stuff (pipes, processes, etc.) that isn't available on playdate. For string formatting we provide

int playdate->system->formatString(char **ret, const char *format, ...)

Allocates a buffer ret and formats a string. Note that the caller is responsible for freeing ret .

I'll file an issue to make a note of this in the docs. I think we might be able to add a shim for sprintf() like we do for malloc() et al. so that you can call it in your code and we route it to the API function. When I looked at that before I thought the varargs would be a problem, but at second glance it looks straightforward if we add vs[n]printf to playdate->system. :thinking:

1 Like

Hi Dave,

Thanks for clarifying. It's probably good to have a note of it in the documentation somewhere as people are bound to run into the same issue and you'll save some time by having this explained somewhere in the docs.

A wrapper of some sorts could be nice to ofc depending on how hard and risky it is to do. Most people are probably fine using the function you listed here as long as they know that they should use it.

Again - thanks for taking the time and explaning it!

Kindly
/Jimmie