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/*
* Copyright (c) 2010, 2012, 2014 Wind River Systems, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @file
* @brief Macros to generate structure member offset definitions
*
* This header contains macros to allow a nanokernel implementation to
* generate absolute symbols whose values represents the member offsets for
* various nanokernel structures. These absolute symbols are typically
* utilized by assembly source files rather than hardcoding the values in
* some local header file.
*
* WARNING: Absolute symbols can potentially be utilized by external tools --
* for example, to locate a specific field within a data structure.
* Consequently, changes made to such symbols may require modifications to the
* associated tool(s). Typically, relocating a member of a structure merely
* requires that a tool be rebuilt; however, moving a member to another
* structure (or to a new sub-structure within an existing structure) may
* require that the tool itself be modified. Likewise, deleting, renaming, or
* changing the meaning of an absolute symbol may require modifications to a
* tool.
*
* The macro "GEN_OFFSET_SYM(structure, member)" is used to generate a single
* absolute symbol. The absolute symbol will appear in the object module
* generated from the source file that utilizes the GEN_OFFSET_SYM() macro.
* Absolute symbols representing a structure member offset have the following
* form:
*
* __<structure>_<member>_OFFSET
*
* This header also defines the GEN_ABSOLUTE_SYM macro to simply define an
* absolute symbol, irrespective of whether the value represents a structure
* or offset.
*
* The following sample file illustrates the usage of the macros available
* in this file:
*
* <START of sample source file: offsets.c>
*
* #include <gen_offset.h>
* /@ include struct definitions for which offsets symbols are to be
* generated @/
*
* #include <kernel_structs.h>
* GEN_ABS_SYM_BEGIN (_OffsetAbsSyms) /@ the name parameter is arbitrary @/
* /@ _kernel_t structure member offsets @/
*
* GEN_OFFSET_SYM (_kernel_t, nested);
* GEN_OFFSET_SYM (_kernel_t, irq_stack);
* GEN_OFFSET_SYM (_kernel_t, current);
* GEN_OFFSET_SYM (_kernel_t, idle);
*
* GEN_ABSOLUTE_SYM (___kernel_t_SIZEOF, sizeof(_kernel_t));
*
* GEN_ABS_SYM_END
* <END of sample source file: offsets.c>
*
* Compiling the sample offsets.c results in the following symbols in offsets.o:
*
* $ nm offsets.o
* 00000000 A ___kernel_t_nested_OFFSET
* 00000004 A ___kernel_t_irq_stack_OFFSET
* 00000008 A ___kernel_t_current_OFFSET
* 0000000c A ___kernel_t_idle_OFFSET
*/
#ifndef _GEN_OFFSET_H
#define _GEN_OFFSET_H
#include <toolchain.h>
#include <stddef.h>
/* definition of the GEN_OFFSET_SYM() macros is toolchain independent */
#define GEN_OFFSET_SYM(S, M) \
GEN_ABSOLUTE_SYM(__##S##_##M##_##OFFSET, offsetof(S, M))
#endif /* _GEN_OFFSET_H */
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