Link failure on the cabal-2.2 branch

[basvandijk]

I get the following on the cabal-2.2 branch:

$ nix-build -A haskell.packages.ghc842.opencv
...
[76 of 77] Compiling OpenCV.Juicy     ( src/OpenCV/Juicy.hs, dist/build/OpenCV/Juicy.p_o )
[77 of 77] Compiling OpenCV.VideoIO.VideoWriter ( src/OpenCV/VideoIO/VideoWriter.hs, dist/build/OpenCV/VideoIO/VideoWriter.p_o )
/nix/store/j75dgadrff2d1fyc4fczmcgqkid2imdx-binutils-2.30/bin/ld: cannot find -lm
/nix/store/j75dgadrff2d1fyc4fczmcgqkid2imdx-binutils-2.30/bin/ld: cannot find -lgcc_s
/nix/store/j75dgadrff2d1fyc4fczmcgqkid2imdx-binutils-2.30/bin/ld: cannot find -lc
/nix/store/j75dgadrff2d1fyc4fczmcgqkid2imdx-binutils-2.30/bin/ld: cannot find -lgcc_s
collect2: error: ld returned 1 exit status

The build succeeds if I run it manually:

$ nix-shell -A haskell.packages.ghc842.opencv.env              
$ cd opencv
$ ghc --make Setup.hs
$ ./Setup configure --enable-tests
$ ./Setup build
$ ./Setup test
Running 2 test suites...
Test suite test-opencv: RUNNING...
Test suite test-opencv: PASS
Test suite logged to: dist/test/opencv-0.0.2.1-test-opencv.log
Test suite doc-images-opencv: RUNNING...
Test suite doc-images-opencv: PASS
Test suite logged to: dist/test/opencv-0.0.2.1-doc-images-opencv.log
2 of 2 test suites (2 of 2 test cases) passed.

[zimbatm]

"cannot find -lm" is quite surprising, it's like it's trying to open -lm as a file. It would be nice to find out how ld is being invoked. Maybe write a wrapper script for ld?

#!/bin/sh
echo "ld args: $*" >&2
exec /nix/store/j75dgadrff2d1fyc4fczmcgqkid2imdx-binutils-2.30/bin/ld "$@"

[basvandijk]

@zimbatm Thanks, that's an excellent idea. In the process of implementing it I removed the --with-ld c++ override in Setup.hs and then the build suddenly succeeded.