From 659fe9fdd14b0772f4e9722b751b9b010665e053 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Mon, 19 Dec 2022 18:56:54 +0100 Subject: stdio-common: Introduce buffers for implementing printf These buffers will eventually be used instead of FILE * objects to implement printf functions. The multibyte buffer is struct __printf_buffer, the wide buffer is struct __wprintf_buffer. To enable writing type-generic code, the header files printf_buffer-char.h and printf_buffer-wchar_t.h define the Xprintf macro differently, enabling Xprintf (buffer) to stand for __printf_buffer and __wprintf_buffer as appropriate. For common cases, macros like Xprintf_buffer are provided as a more syntactically convenient shortcut. Buffer-specific flush callbacks are implemented with a switch statement instead of a function pointer, to avoid hardening issues similar to those of libio vtables. struct __printf_buffer_as_file is needed to support custom printf specifiers because the public interface for that requires passing a FILE *, which is why there is a trapdoor back from these buffers to FILE * streams. Since the immediate user of these interfaces knows when processing has finished, there is no flush callback for the end of processing, only a flush callback for the intermediate buffer flush. Reviewed-by: Adhemerval Zanella --- stdio-common/printf_buffer_flush.c | 42 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 stdio-common/printf_buffer_flush.c (limited to 'stdio-common/printf_buffer_flush.c') diff --git a/stdio-common/printf_buffer_flush.c b/stdio-common/printf_buffer_flush.c new file mode 100644 index 0000000..9b25c0f --- /dev/null +++ b/stdio-common/printf_buffer_flush.c @@ -0,0 +1,42 @@ +/* Flush a struct __printf_buffer. Multibyte version. + Copyright (C) 2022 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include + +#include "printf_buffer-char.h" +#include "Xprintf_buffer_flush.c" + +/* The __printf_buffer_flush_* functions are defined together with + functions that are pulled in by strong references. */ +#ifndef SHARED +# pragma weak __printf_buffer_flush_to_file +#endif /* !SHARED */ + +static void +__printf_buffer_do_flush (struct __printf_buffer *buf) +{ + switch (buf->mode) + { + case __printf_buffer_mode_failed: + return; + case __printf_buffer_mode_to_file: + __printf_buffer_flush_to_file ((struct __printf_buffer_to_file *) buf); + return; + } + __builtin_trap (); +} -- cgit v1.1