linux-kernel - Re: arch/x86/include/asm/current.h:49:9: error: call to undeclared function '__typeof_unqual__'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]

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Message-ID: <9fa81826-8fa6-47e4-a0a2-4916e5d042a7@stanley.mountain>
Date: Wed, 18 Dec 2024 23:14:30 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: Naresh Kamboju <naresh.kamboju@...aro.org>,
	rust-for-linux@...r.kernel.org,
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	lkft-triage@...ts.linaro.org,
	Anders Roxell <anders.roxell@...aro.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: arch/x86/include/asm/current.h:49:9: error: call to undeclared
 function '__typeof_unqual__'; ISO C99 and later do not support implicit
 function declarations [-Wimplicit-function-declaration]

On Wed, Dec 18, 2024 at 05:33:24PM +0100, Uros Bizjak wrote:
> On Wed, Dec 18, 2024 at 5:08 PM Naresh Kamboju
> <naresh.kamboju@...aro.org> wrote:
> >
> > The Rust gcc builds failed due to following build warnings / errors on the
> > x86_64 and arm64 architectures with selftests/rust/config on the Linux
> > next-20241216...next-20241218.
> >
> > First seen on the next-20241216 tag.
> > Good: next-20241213
> > Bad: next-20241216
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> >
> > Anders bisected this regressions and found,
> > # first bad commit:
> >   [20b3c3eccd9361c9976af640be280526bef72248]
> >   percpu: use TYPEOF_UNQUAL() in variable declarations
> >
> > Build log:
> > -------
> > arch/x86/include/asm/current.h:49:9: error: call to undeclared
> > function '__typeof_unqual__'; ISO C99 and later do not support
> > implicit function declarations [-Wimplicit-function-declaration]
> > arch/x86/include/asm/current.h:49:9: error: expected ';' after expression
> > arch/x86/include/asm/current.h:49:9: error: use of undeclared
> > identifier 'pscr_ret__'
> 
> __typeof_unqual__ is a keyword in c23 (and an extension in gcc-14+ and
> clang-19+).
> 
> https://en.cppreference.com/w/c/language/typeof
> https://learn.microsoft.com/en-us/cpp/c-language/typeof-unqual-c?view=msvc-170
> 
> The compiler support is detected in init/Kconfig:
> 
> config CC_HAS_TYPEOF_UNQUAL
>     def_bool $(success,echo 'int foo (int a) { __typeof_unqual__(a) b
> = a; return b; }' | $(CC) -x c - -S -o /dev/null)
> 
> so, if your compiler doesn't support this keyword,
> CC_HAS_TYPEOF_UNQUAL should not be enabled and
> include/linux/compiler.h should disable usage of __typeof_unqual__:
> 
> #if defined(CONFIG_CC_HAS_TYPEOF_UNQUAL) && !defined(__CHECKER__)
> # define TYPEOF_UNQUAL(exp) __typeof_unqual__(exp)
> #else
> # define TYPEOF_UNQUAL(exp) __typeof__(exp)
> #endif
> 
> Can you please investigate what happens here for your build?

This is the bindgen program for generating Rust bindings.  Tuxmake is
using bindgen 0.66.1 and I was able to reproduce the failures with
that version inside a container.  I have bindgen 0.70.1 installed on my
system and that seems to parse __typeof_unqual__ okay.

I don't know how bindgen works.  Maybe the Rust developers can comment?

regards,
dan carpenter