Several modern, currently-supported compiler families are free-to-use for C, C++ and Fortran.
GCC has broad support of modern standards on a very wide range of computing platforms. GCC’s downside in some cases can be slower runtime performance than compilers having less broad language and platform support.
|GNU||gcc: C17||g++ C++20||gfortran: F2018|
|Intel oneAPI||icx: C17||icpx: C++20||ifx: F2018|
|LLVM||clang: C17||clang++: C++20||flang-f18: F2018|
|AOCC||clang: C17||clang++: C++17||flang: F2003|
|NVidia HPC SDK||nvc: C11||nvc++: C++20||nvfortran: F2003|
|IBM OpenXL||xlc: C17||xlc++: C++17||xlf: F2018|
LLVM Clang and Flang have significant industry support, including from Nvidia, and are known for high performance.
IBM OpenXL LLVM-based compilers are currently for POWER CPUs only e.g. ppc64le. IBM OpenXL compilers do not work with a typical x86-based computer.