Re: [PATCH][MSP430] Implement reduced code size printf and puts functions

Corinna Vinschen <[email protected]> Mon, 15 Apr 2019 14:25:13 +0200
Newsgroups	gmane.comp.lib.newlib
Message-ID	<[email protected]>
On Apr 15 12:33, Jozef Lawrynowicz wrote:
> >From d4c48179ea3362b0dea483afba748728fdfa9310 Mon Sep 17 00:00:00 2001
> From: Jozef Lawrynowicz <[email protected]>
> Date: Fri, 12 Apr 2019 11:57:59 +0100
> Subject: [PATCH 1/2] [MSP430][1/2] Copy prerequisite file for "tiny" printf
>  implementation
> 
> Use newlib/libc/stdio/nano-vfprintf.c as baseline for tiny-printf.c
> [...]
> Subject: [PATCH 2/2] [MSP430][2/2] Implement reduced code size "tiny" printf
>  and puts
> 
> "tiny" printf is derived from _vfprintf_r in libc/stdio/nano-vfprintf.c.
> "tiny" puts has been implemented so that it just calls write, without
> any other processing.
> Support for buffering, reentrancy and streams has been removed from
> these functions to achieve reduced code size.
> 
> This reduced code size implementation of printf and puts can be enabled
> in an application by passing "--wrap printf" and "--wrap puts" to the
> GNU linker. This will replace references to "printf" and "puts" in user
> code with "__wrap_printf" and "__wrap_puts" respectively.
> If there is no implementation of these __wrap* functions in user code,
> these "tiny" printf and puts implementations will be linked into the
> final executable.
> 
> The wrapping mechanism is supposed to be invisible to the user:
> - A GCC wrapper option such as "-mtiny-printf" will be added to alias
>   these wrap commands.
> - If the user is unaware of the "tiny" implementation, and chooses to
>   implement their own __wrap_printf and __wrap_puts, their own
>   implementation will be automatically chosen over the "tiny" printf and
>   puts from the library.
> 
> Newlib must be configured with --enable-newlib-nano-formatted-io for 
> the "tiny" printf and puts functions to be built into the library.
> 
> Code size reduction examples:
> printf("Hello World\n")
>   baseline - msp430-elf-gcc gcc-8_3_0-release
>      text    data     bss
>    5638     214      26
>   "tiny" puts enabled
>     text    data     bss
>      714      90      20
> 
> printf("Hello %d\n", a)
>   baseline - msp430-elf-gcc gcc-8_3_0-release
>     text    data     bss
>    10916     614      28
> 
>   "tiny" printf enabled
>     text    data     bss
>     4632     280      20

Pushed.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat
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