Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness

From	Markus Trippelsdorf <markus@trippelsdorf.de>
Newsgroups	linux.kernel
Subject	Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness
Date	2016-10-19 17:40 +0200
Message-ID	<su18f-37s-83@gated-at.bofh.it> (permalink)
References	<stkZj-7hj-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 2016.10.17 at 19:38 +0100, Will Deacon wrote:
> Hi all,
> 
> I'm seeing an arm64 build failure with -rc1 and GCC trunk, although I
> believe that the new compiler behaviour at the heart of the problem
> has the potential to affect other architectures and other pieces of
> kernel code relying on dead-code elimination to remove deliberately
> undefined functions.
> 
> The failure looks like:
> 
>   | drivers/built-in.o: In function `armada_3700_add_composite_clk':
>   |
>   | linux/drivers/clk/mvebu/armada-37xx-periph.c:351:
>   | undefined reference to `____ilog2_NaN'
>   |
>   | linux/drivers/clk/mvebu/armada-37xx-periph.c:351:(.text+0xc72e0):
>   | relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol
>   | `____ilog2_NaN'
>   |
>   | make: *** [vmlinux] Error 1
> 

This is a gcc bug, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72785

-- 
Markus

Thread

Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Will Deacon <will.deacon@arm.com> - 2016-10-17 20:40 +0200
  Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-10-17 21:50 +0200
    Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-10-19 17:10 +0200
      Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Arnd Bergmann <arnd@arndb.de> - 2016-10-19 17:20 +0200
        Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-10-19 17:30 +0200
          Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Arnd Bergmann <arnd@arndb.de> - 2016-10-19 17:50 +0200
        Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Gregory CLEMENT <gregory.clement@free-electrons.com> - 2016-10-19 17:40 +0200
    Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-10-19 17:10 +0200
    Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Will Deacon <will.deacon@arm.com> - 2016-10-19 17:50 +0200
      Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-10-19 18:00 +0200
  Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Markus Trippelsdorf <markus@trippelsdorf.de> - 2016-10-19 17:40 +0200
    Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-19 18:00 +0200
      Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Markus Trippelsdorf <markus@trippelsdorf.de> - 2016-10-19 18:00 +0200
        Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-10-19 18:10 +0200
        Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-19 18:10 +0200
          Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness Will Deacon <will.deacon@arm.com> - 2016-10-19 18:30 +0200

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