Error with kernel-cflags-finder on make

[kilroyjones]

I'm incredibly new to all this, so pardon my ignorance, but I was trying to compile the hello-world example and experienced this error using Mint 20 with kernels 5.4.0.26, 5.6.19, and 5.7.9 (I attempted it on all three of these kernels).

   Compiling bitflags v1.2.1
   Compiling linux-kernel-module v0.1.0 (/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust)
error: failed to run custom build command for `linux-kernel-module v0.1.0 (/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust)`

Caused by:
  process didn't exit successfully: `/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world/target/debug/build/linux-kernel-module-072fd5c94419c165/build-script-build` (exit code: 1)
  --- stdout   Compiling bitflags v1.2.1
   Compiling linux-kernel-module v0.1.0 (/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust)
error: failed to run custom build command for `linux-kernel-module v0.1.0 (/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust)`

Caused by:
  process didn't exit successfully: `/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world/target/debug/build/linux-kernel-module-072fd5c94419c165/build-script-build` (exit code: 1)
  --- stdout
  cargo:rerun-if-env-changed=KDIR
  cargo:rerun-if-env-changed=CLANG
  cargo:rerun-if-changed=kernel-cflags-finder/Makefile

  --- stderr
  kernel-cflags-finder did not succeed
  stdout: 
  stderr: error: unknown warning option '-Wno-unused-but-set-variable'; did you mean '-Wno-unused-const-variable'? [-Werror,-Wunknown-warning-option]
  make[2]: *** [scripts/Makefile.build:275: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/kernel-cflags-finder/dummy.o] Error 1
  make[1]: *** [Makefile:1719: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/kernel-cflags-finder] Error 2
  make: *** [Makefile:33: all] Error 2

make[2]: *** [/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world/Kbuild:7: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world/target/x86_64-linux-kernel/debug/libhello_world.a] Error 101
make[1]: *** [Makefile:1719: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world] Error 2
make: *** [Makefile:4: all] Error 2
  cargo:rerun-if-env-changed=KDIR
  cargo:rerun-if-env-changed=CLANG
  cargo:rerun-if-changed=kernel-cflags-finder/Makefile

  --- stderr
  kernel-cflags-finder did not succeed
  stdout: 
  stderr: error: unknown warning option '-Wno-unused-but-set-variable'; did you mean '-Wno-unused-const-variable'? [-Werror,-Wunknown-warning-option]
  make[2]: *** [scripts/Makefile.build:275: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/kernel-cflags-finder/dummy.o] Error 1
  make[1]: *** [Makefile:1719: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/kernel-cflags-finder] Error 2
  make: *** [Makefile:33: all] Error 2

make[2]: *** [/home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world/Kbuild:7: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world/target/x86_64-linux-kernel/debug/libhello_world.a] Error 101
make[1]: *** [Makefile:1719: /home/kilroy/code/kernel_modules/rust_based/linux-kernel-module-rust/hello-world] Error 2
make: *** [Makefile:4: all] Error 2

I also tried using this branch and have followed all the recommend changes both here and here. It seemed that some of these have already been changed here, such as cflags.

Any advice would be much appreciated.

[alex]

Interesting. What clang version were you using?

[kilroyjones]

Tried it with clang 9 and 10, and both produced the same error.

[alex]

Mmm, not sure off hand. @geofft any idea?

[geofft]

Oh, this is probably also fixed by #227!

[alex]

Optimistically closing this now that #227 is merged. If it's not actually fixed, we can reopen!