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cortex-m-semihosting: make semihosting macros compatible with 1-arg format strings #591

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suaviloquence
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Fixes #581

};
($s:expr, $($tt:tt)*) => {
$crate::export::hstderr_fmt(format_args!(concat!($s, "\n"), $($tt)*))
$crate::export::hstderr_fmt(format_args!("{}\n", format_args!($s, $($tt)*)))
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Is the double nested format_args! required here? Was there some use case that didn't work with the previous method of using concat!?

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Yes, sorry I meant to take a note of it - format_args! doesn't expand captures in the format string literal if it is generated by a macro:

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From rust-lang/rust#106824, it should get flattened into a single format_args!/Arguments call.

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yikes - thanks for the clarification.

@jonathanpallant
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As a point of reference, the semihosting crate does it like this: https://docs.rs/semihosting/0.1.18/src/semihosting/macros.rs.html.

You could make the argument we should deprecate this crate and recommend people use that one.

@suaviloquence
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Anything else I need to do on this PR?

@jonathanpallant
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No, it's all good. I was just letting others have a chance to weigh in.

@jonathanpallant jonathanpallant added this pull request to the merge queue Apr 24, 2025
Merged via the queue into rust-embedded:master with commit c3d664b Apr 24, 2025
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cortex-m-semihosting: hprint! family of macros do not format strings without arguments
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