cmake compiler_error ai_generated true

CMake Error: CXX_STANDARD is set to invalid value '20' — compiler does not support C++20

ID: cmake/cxx-standard-not-supported

Also available as: JSON · Markdown

88%Fix Rate

90%Confidence

3Evidence

2023-01-01First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
3	active	—	—	—

The CXX_STANDARD value (e.g., 20, 23) exceeds what the installed compiler version supports.

generic

92% success Upgrade the compiler to a version supporting the required standard
```
sudo apt install g++-12  # g++-12 supports C++20; g++-13+ for C++23
```
Sources: https://cmake.org/cmake/help/latest/command/find_package.html
88% success Specify the compiler version explicitly
```
cmake -DCMAKE_CXX_COMPILER=/usr/bin/g++-12 ..
```
80% success Lower CXX_STANDARD if the code does not actually use newer features
```
set(CMAKE_CXX_STANDARD 17)  # only if no C++20 features are used
```

Common approaches that don't work:

Set CMAKE_CXX_STANDARD_REQUIRED to OFF to ignore the error 85% fail
Silently falls back to an older standard; code using C++20 features will fail with cryptic template errors.
Add -std=c++20 manually to CMAKE_CXX_FLAGS 72% fail
Bypasses CMake's compiler feature detection; causes duplicate or conflicting flags.