Five free C C++ Fortran compiler families

Five modern, currently-supported compiler families are free-to-use for C, C++ and Fortran.

GCC

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.

Compiler language standard
gcc C17
g++ C++20 with special compile flags needed for initial C++20 module support
gfortran Fortran 2018

Intel

Intel compilers are free to use for any user. The Intel performance libraries like MKL, IPP, and TBB are available at no cost.

Compiler language standard
icc C17
icpc C++17 with increasing C++20 support
ifort Fortran 2018

LLVM

LLVM Clang and Flang have significant industry support, including from Nvidia, and are known for high performance.

Compiler language standard
clang C17
clang++ C++20 with special compile flags needed for initial C++20 module support
flang Fortran 2018 (coming ~2021)

Nvidia

Nvidia HPC SDK is free to use. A key feature of the HPC SDK compilers is intrinsic support for CUDA Fortran.

Compiler language standard
nvc C11
nvc++ C++17
nvfortran Fortran 2003

IBM XL

IBM XL compilers are currently for POWER CPUs only e.g. ppc64le. IBM XL compilers do not work with a typical x86-based computer. If you have a $3000 Raptor IBM POWER9 desktop, then IBM XL may be for you.

The IBM XL compilers are high-performance compilers that have a free community edition. IBM XL Fortran has wide support for Fortran 2008. However, the XL compilers have bugs in newer language support, so be sure to check with another compiler on the IBM system like GCC if a bug is suspected.

Compiler language standard
xlc C11
xlc++ C++14
xlf Fortran 2008

IBM Fortran 2008 reference