Add fmt_print and fmt_println to C API#4789
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vitaut
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Jun 1, 2026
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Thanks for the PR. I think adding fmt_print makes sense as a safe replacement for printf but I don't think we need fmt_println - let's keep the API small for now.
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| constexpr size_t max_args = 16; | ||
| if (num_args > max_args) return fmt_error_invalid_arg; | ||
| constexpr size_t max_c_format_args = 16; | ||
| static int parse_c_format_args( |
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It's not parsing, maybe rename to convert?
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| static int fmt_c_wrapper(const char* fmt, const fmt_arg* args, size_t num_args, | ||
| F&& f) { |
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I don't think this is needed.
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This PR introduces
fmt_print()andfmt_println()macros to the C API, which print to aFILE*stream usingfmt::vprint(stream, fmt, format_args).Additionally, this PR introduces the following helpers in
fmt-c.h:FMT_FORMAT_ARGS(fmt, ...)that abstracts away the macro magic necessary to produce thefmt_argarray, useful for avoiding duplicated logic when declaring additional wrapper macros that expand to calls tofmt_vformator similarfmt_vprint()function used to implement thefmt_print()macrofmt_vprintln()function used to implement thefmt_println()macroand the following helpers in
fmt-c.cc:fmt_c_wrapper()that performs the conversion fromfmt_argtofmt::basic_format_arg, calls the passed lambda, and handles exceptions, to reduce boilerplate and duplication betweenfmt_vformat(),fmt_vprint(), andfmt_vprintln()