in top-level.nix I saw the definition of gcc:

  default-gcc-version = 14;
  gcc = pkgs.${"gcc${toString default-gcc-version}"};

Currently Intel fortran compiler ifx works when compiling hdf5 and openmpi, but does not work when compiling VASP (a proprietary software, its source code is only available after purchase, so I could not provide it here).
ifx complains:

ifx: error #10417: Problem setting up the Intel(R) Compiler compilation environment. Requires 'install path' setting gathered from 'gcc'

In reply to @chn:chn.moe

This is my nix repl history:

nix-repl> :lf github:NixOS/nixpkgs/nixos-unstable
Added 17 variables.

nix-repl> outputs.legacyPackages.x86_64-linux.gcc.cc
«derivation /nix/store/sjzbql9ja7p7c08ziagba11cnvj6lsz9-gcc-14.2.1.20250322.drv»

nix-repl> outputs.legacyPackages.x86_64-linux.gcc14.cc
«derivation /nix/store/f3gx5c6q45nsskjyx451amqmzyvasr90-gcc-14.2.1.20250322.drv»

In reply to @chn:chn.moe

Currently Intel fortran compiler ifx works when compiling hdf5 and openmpi, but does not work when compiling VASP (a proprietary software, its source code is only available after purchase, so I could not provide it here).
ifx complains:

ifx: error #10417: Problem setting up the Intel(R) Compiler compilation environment. Requires 'install path' setting gathered from 'gcc'

In reply to @chn:chn.moe
Many fortran programs in my major does not consist with standard fortran, gfortran will refuse to compile them, while restriction in ifx loose a lot.
And, not sure why, but program compiled using ifx usually gains a huge performance improvement, comparing to gfortran or compiler from AMD (ROCM), even on AMD CPU.

What about packaging ifx?
That is what I tried to do yesterday.

What about packaging ifx?

That is what I tried to do yesterday.