Re: Compilation errors

[Stefano Brivio <sbrivio@redhat.com>]

Hi Fabio,

On Fri, 01 Apr 2022 11:35:13 +0200
"Fabio M. De Francesco" <fmdefrancesco@gmail.com> wrote:

> Hello everybody,
> 
> I've made hundreds of Linux builds and never had problems, but since 
> few days I'm not anymore able to compile the kernel with GCC or Clang.
> 
> I get many errors like the following and the build crashes:
> 
> # CC=gcc-11 make -j12
> [...]
> drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c: In function ‘bnx2x_check_blocks_with_parity3’:
> drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c:4917:4: error: case label does not reduce to an integer constant
>     case AEU_INPUTS_ATTN_BITS_MCP_LATCHED_SCPAD_PARITY:
> [...]
> make[5]: *** [scripts/Makefile.build:289: drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.o] Error 1
> make[4]: *** [scripts/Makefile.build:551: drivers/net/ethernet/broadcom/bnx2x] Error 2
> make[4]: *** Waiting for unfinished jobs....
> 
> One more example...
> 
> # make mrproper
> # CC=clang make -j12
> [...]
> drivers/usb/typec/tcpm/tcpm.c:4724:3: error: case label does not reduce to an integer constant
>    case BDO_MODE_TESTDATA:
>    ^~~~
> make[4]: *** [scripts/Makefile.build:288: drivers/usb/typec/tcpm/tcpm.o] Error 1
> make[3]: *** [scripts/Makefile.build:550: drivers/usb/typec/tcpm] Error 2
> make[2]: *** [scripts/Makefile.build:550: drivers/usb/typec] Error 2
> make[2]: *** Waiting for unfinished jobs....
> 
> Can someone help me to understand what is happening and how to fix this issue?
> Could it depend on a configuration option that, unintentionally enabled, make 
> the build fail whenever "case label does not reduce to an integer constant" is 
> hit? If so, which option?

Those would be warnings, but kernel builds switched to -Werror by
default a while ago, see commit 3fe617ccafd6 ("Enable '-Werror' by
default for all kernel builds") -- meaning that all warnings are
treated as errors. You can disable CONFIG_WERROR:

	scripts/config -d WERROR

to double check. But I guess you just found a source of very useful,
relatively trivial patches. :) Of course, chances are that some of
those are already fixed in some other tree.

As to why it started happening for you recently: maybe you just
switched to gcc 11 and a newer version of clang? Can you try with
gcc 10 if you have it still installed?

-- 
Stefano