Are you tired of dealing with compatibility issues in your C++ projects on CentOS 7? Do you find yourself tangled in a web of complex build configurations and compiler versions? Well, worry no more! In this comprehensive guide, we’ll take you on a journey to explore the wonders of CMake 3.17.5 on CentOS 7, specifically focusing on the nuances of ISO C90 and CMAKE_CXX_STANDARD=11.
What is CMake and why do we need it?
CMake is an open-source, cross-platform build system generator that allows developers to create and manage build processes for their projects. It’s a crucial tool for any serious C++ developer, as it provides a unified way to create build configurations that work across different platforms and compilers.
On CentOS 7, CMake 3.17.5 is the default version, and it’s essential to understand how to harness its power to create efficient and compatible build processes.
The Importance of ISO C90 and CMAKE_CXX_STANDARD=11
In the world of C++, there are multiple standards and versions that can cause compatibility issues if not handled correctly. ISO C90, also known as C89 or ANSI C, is an older standard that was widely adopted in the past. However, with the advent of modern C++ standards, such as C++11, C++14, and C++17, it’s essential to understand how to configure your build process to use the correct standard.
CMAKE_CXX_STANDARD=11 is a crucial variable in CMake that specifies the C++ standard to use for compilation. By setting it to 11, we’re telling CMake to use the C++11 standard, which is a significant improvement over the older ISO C90 standard.
Configuring CMake for ISO C90 and CMAKE_CXX_STANDARD=11
Now that we’ve covered the basics, let’s dive into the configuration process. Create a new directory for your project and navigate to it in your terminal:
mkdir myproject
cd myprojectCreate a new file called `CMakeLists.txt` and add the following code:
cmake_minimum_required(VERSION 3.17.5)
project(myproject)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
add_executable(${PROJECT_NAME} main.cpp)
In this configuration, we’re telling CMake to:
- Use version 3.17.5 or higher
- Set the project name to `myproject`
- Specify the C++ standard to use as C++11 (CMAKE_CXX_STANDARD=11)
- Enforce the use of the specified standard (CMAKE_CXX_STANDARD_REQUIRED=ON)
- Create an executable called `myproject` from the `main.cpp` file
Understanding the CMakeCache.txt File
After running the `cmake` command, you’ll notice a file called `CMakeCache.txt` generated in your project directory. This file contains a cache of the build configuration settings used by CMake.
Let’s examine the contents of this file:
// The C compiler identification is GNU 4.8.5
CMAKE_C_COMPILER_ID=GNU
// The CXX compiler identification is GNU 4.8.5
CMAKE_CXX_COMPILER_ID=GNU
// The CXX standard conformance
CMAKE_CXX_STANDARD=11
// The CXX standard required is 11
CMAKE_CXX_STANDARD_REQUIRED=ON
As you can see, the `CMakeCache.txt` file contains information about the compiler identification, C++ standard conformance, and the required standard.
Building and Running the Project
Now that we have our `CMakeLists.txt` file configured, let’s build and run our project. Run the following commands in your terminal:
cmake .
make
./myproject
The first command generates the build configuration, the second command builds the executable, and the third command runs the executable.
Troubleshooting Common Issues
During the build process, you might encounter issues related to compatibility or compiler versions. Here are some common issues and their solutions:
-
Error: C++11 is not supported on this platform
Solution: Check your compiler version. Make sure you’re using a compatible version that supports C++11.
-
Error: Unknown CMAKE_CXX_STANDARD value ’11’
Solution: Update your CMake version to 3.17.5 or higher, which supports CMAKE_CXX_STANDARD=11.
-
Warning: CMAKE_CXX_STANDARD is set to 11, but the compiler only supports up to C++03
Solution: Check your compiler version and update it to a version that supports C++11.
Conclusion
In this article, we’ve explored the world of CMake 3.17.5 on CentOS 7, focusing on the importance of ISO C90 and CMAKE_CXX_STANDARD=11. By following the instructions and troubleshooting tips provided, you should be able to create efficient and compatible build configurations for your C++ projects.
Remember, mastering CMake takes practice and patience. Experiment with different configurations and standards to become proficient in creating complex build processes.
| CMake Variable | Description |
|---|---|
| CMAKE_CXX_STANDARD | Specifies the C++ standard to use for compilation. |
| CMAKE_CXX_STANDARD_REQUIRED | Enforces the use of the specified C++ standard. |
| CMAKE_C_COMPILER_ID | Contains information about the C compiler identification. |
| CMAKE_CXX_COMPILER_ID | Contains information about the C++ compiler identification. |
We hope you’ve enjoyed this comprehensive guide to CMake 3.17.5 on CentOS 7. Stay tuned for more tutorials and guides on mastering CMake and C++ development!
Frequently Asked Question
Get answers to your burning questions about CMake 3.17.5 on CentOS 7, where CMAKE_CXX_STANDARD is set to 11, but the compiler insists on using ISO C90.
Why is CMake 3.17.5 on CentOS 7 using ISO C90 instead of C++11?
This is because the default standard for the GNU Compiler Collection (GCC) on CentOS 7 is set to C90. Even though you’ve specified CMAKE_CXX_STANDARD=11, the compiler doesn’t automatically switch to C++11 mode. You need to explicitly set the standard using the -std=c++11 flag.
How do I force CMake to use C++11 standard instead of C90?
You can add the following line to your CMakeLists.txt file: set(CMAKE_CXX_FLAGS “${CMAKE_CXX_FLAGS} -std=c++11”). This will instruct the compiler to use the C++11 standard.
Will setting CMAKE_CXX_STANDARD=11 automatically add the -std=c++11 flag?
No, it won’t. CMAKE_CXX_STANDARD only sets the standard for the compiler, but it doesn’t automatically add the required flags. You need to explicitly set the flags using CMAKE_CXX_FLAGS.
What are the implications of using ISO C90 instead of C++11?
Using ISO C90 instead of C++11 can lead to compatibility issues and limitations. C++11 introduces many features and improvements that are not available in C90, such as rvalue references, auto keyword, and constexpr. If your code relies on these features, it won’t compile or run correctly with the C90 standard.
Can I use a newer version of CMake to avoid this issue?
Yes, newer versions of CMake (starting from 3.20) automatically add the required flags based on the CMAKE_CXX_STANDARD setting. So, if you can upgrade to a newer version, you won’t need to explicitly set the flags.
