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Date: Tue, 6 Dec 2022 11:36:24 +0100
From: Yuriy Chernyshov <>
Subject: Various conflicts with linux system headers (ioctl.h)


I am trying to build DBMS software (ydb from with musl-libc.
So far, I have run into certain problems.

As YDB uses ioctl.h, it has to include both ioctl.h and certain headers
from linux/ itself. This gives me a bunch of conflicts around _IOC macros
family being defined by both:

The error looks as follows:

contrib/libs/musl/arch/generic/bits/ioctl.h:7:9: error: '_IOW' macro
> redefined [-Werror,-Wmacro-redefined]
> #define _IOW(a,b,c) _IOC(_IOC_WRITE,(a),(b),sizeof(c))
>         ^
> contrib/libs/linux-headers/asm-generic/ioctl.h:90:9: note: previous
> definition is here
> #define _IOW(type,nr,size)
>  _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))

The following workaround helps, but looks quite ugly:

--- arch/generic/bits/ioctl.h (b4624b83eafbdd5f2e2c37374d62426c27687f35)
> +++ arch/generic/bits/ioctl.h (d545cbc1ae3f5c9132eb26b176bef3638c9d8063)
> @@ -1,3 +1,9 @@
> +#undef _IO
> +#undef _IOC
> +#undef _IOR
> +#undef _IOW
> +#undef _IOWR
> +
>  #define _IOC(a,b,c,d) ( ((a)<<30) | ((b)<<8) | (c) | ((d)<<16) )
>  #define _IOC_NONE  0U
>  #define _IOC_WRITE 1U

Is it possible to get official solution for the macro conflict?

NB: we have to use linux/fs.h in order to get BLKGETSIZE64 constant defined
which is missing in sys/ioctl.h.

Another conflict is in NGROUPS_MAX value: musl sets it to 32, while Linux
itself (starting from 2.6.4, which is below the minimal version recommended
by musl) sets it to 65536.

It would be nice to have this value increased in musl itself.


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