############################################################################
#
# Copyright (c) 2018 PX4 Development Team. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in
# the documentation and/or other materials provided with the
# distribution.
# 3. Neither the name PX4 nor the names of its contributors may be
# used to endorse or promote products derived from this software
# without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
############################################################################
#查找该目录的绝对路径
include(px4_list_make_absolute)
#=============================================================================
#
# px4_add_module
#
# This function builds a static library from a module description.
#
# Usage:
# px4_add_module(MODULE <string>
# MAIN <string>
# [ STACK_MAIN <string> ]
# [ STACK_MAX <string> ]
# [ COMPILE_FLAGS <list> ]
# [ INCLUDES <list> ]
# [ DEPENDS <string> ]
# [ SRCS <list> ]
# [ MODULE_CONFIG <list> ]
# [ EXTERNAL ]
# [ DYNAMIC ]
# )
###解释各个参数，并且说明作用
# Input:
# MODULE : unique name of module
# MAIN : entry point
# STACK : deprecated use stack main instead
# STACK_MAIN : size of stack for main function
# STACK_MAX : maximum stack size of any frame
# COMPILE_FLAGS : compile flags
# LINK_FLAGS : link flags
# SRCS : source files
# MODULE_CONFIG : yaml config file(s)
# INCLUDES : include directories
# DEPENDS : targets which this module depends on
# EXTERNAL : flag to indicate that this module is out-of-tree
# DYNAMIC : don't compile into the px4 binary, but build a separate dynamically loadable module (posix)
# UNITY_BUILD : merge all source files and build this module as a single compilation unit
#
# Output:
# Static library with name matching MODULE.
# (Or a shared library when DYNAMIC is specified.)
#
# Example:
# px4_add_module(MODULE test
# SRCS
# file.cpp
# STACK_MAIN 1024
# DEPENDS
# git_nuttx
# )
#
function(px4_add_module)
##px4_parse_function_args作用实现解析命令并转为参数列表，
px4_parse_function_args(
NAME px4_add_module
ONE_VALUE MODULE MAIN STACK_MAIN STACK_MAX PRIORITY
MULTI_VALUE COMPILE_FLAGS LINK_FLAGS SRCS INCLUDES DEPENDS MODULE_CONFIG
OPTIONS EXTERNAL DYNAMIC UNITY_BUILD
REQUIRED MODULE MAIN
ARGN ${ARGN})
#如果某个module中包含UNITY_BUILD并且采用nutxx系统，则进入下面函数
#通过代码查找，能找到mavlink是通过下面函数进行编译
if(UNITY_BUILD AND (${PX4_PLATFORM} STREQUAL "nuttx"))
# build standalone test library to catch compilation errors and provide sane output构建独立的测试库以捕获编译错误并提供合理的输出
add_library(${MODULE}_original STATIC EXCLUDE_FROM_ALL ${SRCS})
#按照顺序将各个依赖包添加进编译列表
if(DEPENDS)
add_dependencies(${MODULE}_original ${DEPENDS})
endif()
#添加库的引用目录
if(INCLUDES)
target_include_directories(${MODULE}_original PRIVATE ${INCLUDES})
endif()
#添加编译命令
target_compile_definitions(${MODULE}_original PRIVATE PX4_MAIN=${MAIN}_app_main)
target_compile_definitions(${MODULE}_original PRIVATE MODULE_NAME="${MAIN}_original")
# unity build
add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${MODULE}_unity.cpp
COMMAND cat ${SRCS} > ${CMAKE_CURRENT_BINARY_DIR}/${MODULE}_unity.cpp
DEPENDS ${MODULE}_original ${DEPENDS} ${SRCS}
COMMENT "${MODULE} merging source"
WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
)
set_source_files_properties(${CMAKE_CURRENT_BINARY_DIR}/${MODULE}_unity.cpp PROPERTIES GENERATED true)
add_library(${MODULE} STATIC EXCLUDE_FROM_ALL ${CMAKE_CURRENT_BINARY_DIR}/${MODULE}_unity.cpp)
target_include_directories(${MODULE} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
if(COMPILE_FLAGS)
target_compile_options(${MODULE}_original PRIVATE ${COMPILE_FLAGS})
endif()
if(DEPENDS)
# using target_link_libraries for dependencies provides linking
# as well as interface include and libraries
#使用目标链接库作为依赖项提供链接以及接口包含和库
foreach(dep ${DEPENDS})
#get_target_property（VAR target property)从一个目标中获取一个属性值
get_target_property(dep_type ${dep} TYPE)
#判断是否为静态库
if (${dep_type} STREQUAL "STATIC_LIBRARY")
target_link_libraries(${MODULE}_original PRIVATE ${dep})
else()
add_dependencies(${MODULE}_original ${dep})
endif()
endforeach()
endif()
elseif(DYNAMIC AND MAIN AND (${PX4_PLATFORM} STREQUAL "posix"))
add_library(${MODULE} SHARED ${SRCS})
target_compile_definitions(${MODULE} PRIVATE ${MAIN}_main=px4_module_main)
set_target_properties(${MODULE} PROPERTIES
PREFIX ""
SUFFIX ".px4mod"
)
target_link_libraries(${MODULE} PRIVATE px4)
if(APPLE)
# Postpone resolving symbols until loading time, which is the default on most systems, but not Mac.
#将解析符号的时间推迟到加载时间，这是大多数系统的默认时间，而不是Mac。
set_target_properties(${MODULE} PROPERTIES LINK_FLAGS "-undefined dynamic_lookup")
endif()
else()
add_library(${MODULE} STATIC EXCLUDE_FROM_ALL ${SRCS})
endif()
# all modules can potentially use parameters and uORB
#所有的模块都会使用参数和uorb
add_dependencies(${MODULE} uorb_headers)
if(NOT DYNAMIC)
target_link_libraries(${MODULE} PRIVATE prebuild_targets parameters_interface px4_layer px4_platform systemlib)
set_property(GLOBAL APPEND PROPERTY PX4_MODULE_LIBRARIES ${MODULE})
set_property(GLOBAL APPEND PROPERTY PX4_MODULE_PATHS ${CMAKE_CURRENT_SOURCE_DIR})
px4_list_make_absolute(ABS_SRCS ${CMAKE_CURRENT_SOURCE_DIR} ${SRCS})
set_property(GLOBAL APPEND PROPERTY PX4_SRC_FILES ${ABS_SRCS})
endif()
# set defaults if not set 设置默认参数
set(MAIN_DEFAULT MAIN-NOTFOUND)
set(STACK_MAIN_DEFAULT 2048)
set(PRIORITY_DEFAULT SCHED_PRIORITY_DEFAULT)
foreach(property MAIN STACK_MAIN PRIORITY)
if(NOT ${property})
set(${property} ${${property}_DEFAULT})
endif()
set_target_properties(${MODULE} PROPERTIES ${property} ${${property}})
endforeach()
# default stack max to stack main设置最大堆栈值或者将STACK_MAIN设置为最大堆栈值
if(NOT STACK_MAX)
set(STACK_MAX ${STACK_MAIN})
endif()
set_target_properties(${MODULE} PROPERTIES STACK_MAX ${STACK_MAX})
if(${PX4_PLATFORM} STREQUAL "nuttx")
target_compile_options(${MODULE} PRIVATE -Wframe-larger-than=${STACK_MAX})
endif()
# MAIN 设置module私有编译目标（编译预处理）
if(MAIN)
target_compile_definitions(${MODULE} PRIVATE PX4_MAIN=${MAIN}_app_main)
target_compile_definitions(${MODULE} PRIVATE MODULE_NAME="${MAIN}")
else()
message(FATAL_ERROR "MAIN required")
endif()
if(COMPILE_FLAGS)
target_compile_options(${MODULE} PRIVATE ${COMPILE_FLAGS})
endif()
if(INCLUDES)
target_include_directories(${MODULE} PRIVATE ${INCLUDES})
endif()
if(DEPENDS)
# using target_link_libraries for dependencies provides linking
# as well as interface include and libraries
foreach(dep ${DEPENDS})
get_target_property(dep_type ${dep} TYPE)
if (${dep_type} STREQUAL "STATIC_LIBRARY")
target_link_libraries(${MODULE} PRIVATE ${dep})
else()
add_dependencies(${MODULE} ${dep})
endif()
endforeach()
endif()
foreach (prop LINK_FLAGS STACK_MAIN MAIN PRIORITY)
if (${prop})
set_target_properties(${MODULE} PROPERTIES ${prop} ${${prop}})
endif()
endforeach()
if(MODULE_CONFIG)
foreach(module_config ${MODULE_CONFIG})
set_property(GLOBAL APPEND PROPERTY PX4_MODULE_CONFIG_FILES ${CMAKE_CURRENT_SOURCE_DIR}/${module_config})
endforeach()
endif()
endfunction()
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