[lapack-reference] build failure - gfortran required?

[SamuelMarks]

Host Environment

• OS: macOS 11.1 (20C69)
• Compiler:
  Apple clang version 12.0.0 (clang-1200.0.32.29)
  Target: x86_64-apple-darwin20.2.0
  Thread model: posix
  InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

To Reproduce
Steps to reproduce the behavior:
./vcpkg install dlib

Starting package 6/10: lapack-reference:x64-osx

Failure logs

Building package lapack-reference[blas-select,core,noblas]:x64-osx...
-- Downloading https://github.com/Reference-LAPACK/lapack/archive/v3.8.0.tar.gz -> Reference-LAPACK-lapack-v3.8.0.tar.gz...
-- Extracting source /private/tmp/vcpkg/downloads/Reference-LAPACK-lapack-v3.8.0.tar.gz
-- Using source at /private/tmp/vcpkg/buildtrees/lapack-reference/src/v3.8.0-954f10683f.clean
-- The Fortran compiler identification is unknown
CMake Error at scripts/cmake/vcpkg_find_fortran.cmake:127 (message):
  Unable to find a Fortran compiler using 'CMakeDetermineFortranCompiler'.
  Please install one (e.g.  gfortran) and make it available on the PATH!
Call Stack (most recent call first):
  ports/lapack-reference/portfile.cmake:50 (vcpkg_find_fortran)
  scripts/ports.cmake:142 (include)


Error: Building package lapack-reference:x64-osx failed with: BUILD_FAILED
Please ensure you're using the latest portfiles with `./vcpkg update`, then
submit an issue at https://github.com/Microsoft/vcpkg/issues including:
  Package: lapack-reference:x64-osx
  Vcpkg version: 2021-01-13-unknownhash

Additional context
Fortran is required for this. So I could just brew install fortran. But I'm pretty sure this can be built without Fortran at all, see www.netlib.org/lapack/lawnspdf/lawn270.pdf http://www.netlib.org/lapack/

You will learn how you can directly run LAPACKE from VS Studio (just C code, no Fortran!!!). LAPACK now offers Windows users the ability to code in C using Microsoft Visual Studio and link to LAPACK Fortran libraries without the need of a vendor-supplied Fortran compiler add-on.

Unless that's just for LAPACKE?

Any I'm not sure if there's a better way of raising missing system dependency errors in vcpkg… might be friendlier to new users (tell them what to apt install brew install etc.)

[Neumann-A]

Unless that's just for LAPACKE?

it is just LAPACKE.

Lapack needs a CMake visible Fortran compiler installed on the system.

[NancyLi1013]

Hi @SamuelMarks

Thanks for posting this issue.

I think this comment may answer your question #12805 (comment).

CMake Error at scripts/cmake/vcpkg_find_fortran.cmake:127 (message):
  Unable to find a Fortran compiler using 'CMakeDetermineFortranCompiler'.
  Please install one (e.g.  gfortran) and make it available on the PATH!

Currently, the error info is clear that you need to install gfortran on your machine.

So please brew install fortran and rebuild this port.

[SamuelMarks]

@Neumann-A Ah okay, yeah was worried about that. Anyway, ended up with a different issue on dlib post-compilation so check that issue to follow the story further 📦