Cross-Platform Compilation
Cross-platform compilation empowers you to build C/C++ applications that run on different operating systems without rewriting the entire codebase.
The Challenge
Compilers and linkers on different platforms have variations in syntax, standard libraries, and available functions. Code written for one platform might not compile or run correctly on another.
Cross-platform compilation tackles this challenge by building the program for a target platform from a single codebase running on a development machine.
Strategies for Cross-Platform
Conditional Compilation:
Employ
#ifdef
,#ifndef
,#else
, and#endif
directives to conditionally include code blocks based on pre-defined macros. You can define these macros based on the target platform during the build process.
#ifdef WINDOWS
#include <windows.h>
#else
#include <unistd.h>
#endif
// Code using platform-specific headers
Compiler and Linker Flags:
Different platforms might require specific compiler and linker flags for optimization or compatibility. CMake allows setting these flags based on the target platform.
if(CMAKE_SYSTEM_NAME MATCHES "Linux")
target_compile_features(MyProgram PRIVATE cxx11) # Enable C++11 for Linux
endif()
if(CMAKE_SYSTEM_NAME MATCHES "Windows")
target_link_libraries(MyProgram PRIVATE user32 gdi32) # Link with Windows UI libraries
endif()
CMake supports defining toolchain files that specify the compiler, linker, and their flags for various platforms. This provides a centralized location for platform-specific configurations.
CMake excels at streamlining cross-platform builds. It offers features like:
Platform Detection: CMake can identify the current development platform.
Conditional Statements: Use CMake's
if
,else
, andendif
statements to manage platform-specific configurations.Target Properties: Set compiler and linker flags for different platforms using target properties.
Toolchain Files: Create reusable toolchain files for various platforms.
Building a Simple Cross-Platform Application
Scenario:
You're developing a text processing application that needs to access the file system. You want to build it for both Linux and Windows.
The CMakeLists.txt:
cmake_minimum_required(VERSION 3.0)
project(MyTextProcessor)
# Define a function to access the file system (implementation details omitted)
function(access_file FILENAME)
if(CMAKE_SYSTEM_NAME MATCHES "Linux")
# Use POSIX functions
message("Using POSIX functions for file access")
else()
# Use Windows API functions
message("Using Windows API functions for file access")
endif()
# Implement file access logic based on the platform
endfunction(access_file)
# Source files
add_executable(MyTextProcessor main.cpp)
# Call the access_file function during compilation
add_custom_command(TARGET MyTextProcessor PRE_BUILD
COMMAND access_file
COMMENT "Determine file access method based on platform"
)
Explanation:
The
access_file
function uses conditional statements to determine the platform and choose the appropriate file access method (not shown here for brevity).A custom command is added to call the
access_file
function before building the executable. This ensures the platform-specific code is included based on the detected platform.