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RIOT/cpu/avr8_common/include/flash_utils_arch.h
Marian Buschsieweke cee7cccfd0
cpu/avr8_common/flash_utils: use C and linker for aliases
`flash_<funcname>()` is implemented by `<funcname>_P()` provided by
the AVR libc on AVR targets. Previously, the preprocessor was used
to do the aliasing, but this causes issues with LLVM: The signatures of
e.g. `printf_P()` expects `const char *`, whereas flash utils expects
`FLASH_ATTR const char *`. For GCC this will just implicitly drop the
`FLASH_ATTR`, while it requires an explicit cast for LLVM.

To implement the explicit cast, `static inline` function wrappers
where used instead where possible. But for the variadic functions
(e.g. `printf(fmt, ...)`) the linker is used to provide the aliases,
as there is no way to pass the variadic functions throw in C. The
alternative would be to implement `flash_printf()` by calling
`vprintf_P()`, but that increased ROM size quite a bit.

Finally, a work around for a bug in Ubuntu's toolchain has been added:
An unused function that calls to `printf_P()`, `fprintf_P()` and
`snprintf_P()`. Since this function is garbage collected anyway, it
has no impact on the generated ELF file.
2023-11-10 14:54:22 +01:00

109 lines
2.7 KiB
C

/*
* Copyright (C) 2022 Otto-von-Guericke-Universität Magdeburg
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpu_avr8_common
* @{
*
* @file
* @brief Implementation of flash_utils
*
* @author Marian Buschsieweke <marian.buschsieweke@ovgu.de>
*
*/
#ifndef FLASH_UTILS_ARCH_H
#define FLASH_UTILS_ARCH_H
#include <stdio.h>
#include <stdarg.h>
#include <avr/pgmspace.h>
#ifdef __cplusplus
extern "C" {
#endif
/* this is documented in sys/include/flash_utils.h - let's not confuse
* Doxygen */
#ifndef DOXYGEN
#define FLASH_ATTR __flash
#define PRIsflash "S"
#define TO_FLASH(x) __extension__({static FLASH_ATTR const char __c[] = (x); &__c[0];})
static inline int flash_strcmp(const char *ram, FLASH_ATTR const char *flash)
{
return strcmp_P(ram, (const char *)flash);
}
static inline int flash_strncmp(const char *ram, FLASH_ATTR const char *flash, size_t n)
{
return strncmp_P(ram, (const char *)flash, n);
}
static inline size_t flash_strlen(FLASH_ATTR const char *flash)
{
return strlen_P((const char *)flash);
}
static inline char * flash_strcpy(char *ram, FLASH_ATTR const char *flash)
{
return strcpy_P(ram, (const char *)flash);
}
static inline char * flash_strncpy(char *ram, FLASH_ATTR const char *flash, size_t n)
{
return strncpy_P(ram, (const char *)flash, n);
}
static inline int flash_vprintf(FLASH_ATTR const char *flash, va_list args)
{
/* vprintf_P() is not provided by avr-libc. But vfprintf_P() with
* stdout as stream can be used to implement it */
return vfprintf_P(stdout, (const char *)flash, args);
}
static inline int flash_vfprintf(FILE *stream, FLASH_ATTR const char *flash,
va_list args)
{
return vfprintf_P(stream, (const char *)flash, args);
}
static inline int flash_vsnprintf(char *buf, size_t buf_len,
FLASH_ATTR const char *flash, va_list args)
{
return vsnprintf_P(buf, buf_len, (const char *)flash, args);
}
static inline void flash_puts(FLASH_ATTR const char *flash)
{
puts_P((const char *)flash);
}
static inline void * flash_memcpy(void *dest, FLASH_ATTR const void *src,
size_t n)
{
return memcpy_P(dest, (const void *)src, n);
}
/* aliases need to be provided by the linker, as passing through va-args is
* not possible */
int flash_printf(FLASH_ATTR const char *flash, ...);
int flash_fprintf(FILE *stream, FLASH_ATTR const char *flash, ...);
int flash_snprintf(char *buf, size_t buf_len, FLASH_ATTR const char *flash, ...);
#endif /* Doxygen */
#ifdef __cplusplus
}
#endif
/** @} */
#endif /* FLASH_UTILS_ARCH_H */