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Date:   Tue, 14 Aug 2018 10:09:04 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     linux-kernel@vger.kernel.org
Cc:     Rik van Riel <riel@surriel.com>, Mike Galbraith <efault@gmx.de>,
        Dave Hansen <dave.hansen@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Build failures with gcc 4.5 and older
Message-ID: <20180814170904.GA12768@roeck-us.net>
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Hi,

Since commit c1a2f7f0c0645 ("mm: Allocate the mm_cpumask
(mm->cpu_bitmap[]) dynamically based on nr_cpu_ids"), building
the Linux kernel with gcc version 4.5 and older fails as follows.

In file included from ./include/linux/mm.h:17:0,
                 from ./include/linux/pid_namespace.h:7,
		 from ./include/linux/ptrace.h:10,
		 from arch/openrisc/kernel/asm-offsets.c:32:
./include/linux/mm_types.h:497:16: error: flexible array member in otherwise empty struct

This is just an example with gcc 4.5.1 for or32. I have seen the problem
with gcc 4.4 (for unicore32) as well.

Does that mean that gcc 4.5 and older are now officially no longer
supported for compiling the kernel ?

If so, would it make sense to update include/linux/compiler-gcc.h
accordingly ?

Thanks,
Guenter