From mboxrd@z Thu Jan  1 00:00:00 1970
From: haolee.swjtu@gmail.com (Hao Lee)
Date: Tue, 22 Mar 2016 19:24:38 +0800
Subject: Is it possible to turn off the gcc optimization when compiling
	kernel?
In-Reply-To: <20160321095151.GB7516@osadl.at>
References: <CA+PpKPn6u3-dMGxCqTd2ZQTTu2AF7+Pfw9=SqeaibiGN0TxOSg@mail.gmail.com>
	<20160321095151.GB7516@osadl.at>
Message-ID: <CA+PpKPm=eHxK5oj39r8nrT6XGA4qo6XKMNRcgcNCNdGQW_SPvw@mail.gmail.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

On Mon, Mar 21, 2016 at 5:51 PM, Nicholas Mc Guire <der.herr@hofr.at> wrote:
> You can not turn it off in all functions as some need particluar
> optimization flags to comile at all, but you can pass
> individual CFLAGS per file via the Makefile
>
> CFLAGS_target.o = -O0 or -flags-to-use
>
> aswell as remove specific CFLAGS with
>
> CFLAGS_REMOVE_target.o = -flags-to-remove
>
> but if you want to debug the kernel it is most likely not
> a good idea to try and disable optimization as the code you then
> are debugging might not have that much to do with the final code
> once optimization is on again. So simply generate the .lst file
> of the target you are trying to debug e.g. for kernel/sched/core.c:
>
> make kernel/sched/core.lst
>
> and then use that .lst file to understand the output of gdb you
> are inspecting.

Thanks for your reply!
Besides,I also find that use "gcc -c -Q -O1 --help=optimizers" can
print the exact set of optimizations.

regards,
Hao Lee