allow developer to select desired implementation of stdin, etc. #1900

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opened 2024-09-03 21:03:26 -05:00 by gneverov · 5 comments

gneverov commented

2024-09-03 21:03:26 -05:00

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picolibc_interface.c currently defines strong symbols for stdin, stdout, and stderr that use the implementation from pico_stdio. There is no way for the developer to override this behavior.

Use cases

if picolibc was compiled with POSIX_IO, then picolibc already defines weak versions of stdin, etc.. Probably the developer intends to use this implementation, but it is silently overridden by the pico-sdk's implementation, which uses strong symbols.
the developer might define their own symbols for stdin, etc. and doesn't want them overridden or in conflict with what pico-sdk defines.

[picolibc_interface.c](https://github.com/raspberrypi/pico-sdk/blob/develop/src/rp2_common/pico_clib_interface/picolibc_interface.c) currently defines strong symbols for stdin, stdout, and stderr that use the implementation from [pico_stdio](https://github.com/raspberrypi/pico-sdk/tree/develop/src/rp2_common/pico_stdio). There is no way for the developer to override this behavior. ### Use cases - if picolibc was compiled with POSIX_IO, then picolibc already defines weak versions of stdin, etc.. Probably the developer intends to use this implementation, but it is silently overridden by the pico-sdk's implementation, which uses strong symbols. - the developer might define their own symbols for stdin, etc. and doesn't want them overridden or in conflict with what pico-sdk defines.

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vazhnov commented

2026-06-16 04:10:39 -05:00

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Is it fixed by https://github.com/raspberrypi/pico-sdk/pull/2935 ?

gneverov commented

2026-06-17 13:29:28 -05:00

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I'm not sure. I resolved my original issue by creating my own "interface.c" rather than relying on the built-in ones. I'm fine with closing this issue.

vazhnov commented

2026-06-17 13:37:16 -05:00

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@gneverov , before to close the issue, you can share your recipe with others :)

kilograham commented

2026-06-18 07:47:27 -05:00

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yeah, i think, leave this open, as it is a reasonable enhancement

gneverov commented

2026-06-18 11:05:27 -05:00

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@vazhnov, @kilograham mentioned at the time that the C lib interface system is user extensible. You can define the CMake PICO_CLIB variable to point to your own implementation instead of using a built-in one.

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