Subject: Re: [PATCH v2] powerpc: Blacklist GCC 5.4 6.1 and 6.2

From: Segher Boessenkool <[email-masked]>
Date: Mon, 13 Feb 2017 09:44:37 -0600

Hi Cyril,

On Mon, Feb 13, 2017 at 02:35:36PM +1100, Cyril Bur wrote:
> A bug in the -02 optimisation of GCC 5.4 6.1 and 6.2 causes
> setup_command_line() to not pass the correct first argument to strcpy
> and therefore not actually copy the command_line.

There is no such thing as an "-O2 optimisation".

> At the time of writing GCC 5.4 is the most recent and is affected. GCC
> 6.3 contains the backported fix, has been tested and appears safe to
> use.

6.3 is (of course) the newer release; 5.4 is a maintenance release of
a compiler that is a year older.

> +# - gcc-5.4, 6.1, 6.2 don't copy the command_line around correctly

> +		echo -n '*** GCC-5.4 6.1 6.2 have a bad -O2 optimisation ' ; \
> +		echo 'which will cause lost command_line options (at least).' ; \

Maybe something more like

"GCC 5.4, 6.1, and 6.2 have a bug that results in a kernel that does
not boot.  Please use GCC 6.3 or later.".

Please mention the GCC PR # somewhere in the code, too?

Segher