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From: Richard Henderson <rth@twiddle.net>
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Date: Mon, 10 Apr 2017 10:49:12 -0700
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Subject: Re: [Qemu-devel] [PATCH fix for-2.9] cpus: fix wrong define name
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To: Greg Kurz <groug@kaod.org>, Peter Maydell <peter.maydell@linaro.org>
Cc: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, QEMU Developers <qemu-devel@nongnu.org>, Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, David Gibson <david@gibson.dropbear.id.au>

On 04/10/2017 10:44 AM, Greg Kurz wrote:
> On Mon, 10 Apr 2017 18:29:57 +0100
> Peter Maydell <peter.maydell@linaro.org> wrote:
>
>> On 10 April 2017 at 18:26, Richard Henderson <rth@twiddle.net> wrote:
>>> On 04/09/2017 11:06 PM, Nikunj A Dadhania wrote:
>>>> --- a/cpus.c
>>>> +++ b/cpus.c
>>>> @@ -202,7 +202,7 @@ void qemu_tcg_configure(QemuOpts *opts, Error **errp)
>>>>              } else if (use_icount) {
>>>>                  error_setg(errp, "No MTTCG when icount is enabled");
>>>>              } else {
>>>> -#ifndef TARGET_SUPPORT_MTTCG
>>>> +#ifndef TARGET_SUPPORTS_MTTCG
>>>
>>>
>>> This sort of thing is why glibc moved to using -Wundef.
>>>
>>> It would be a huge amount of work to convert our existing sources, but it
>>> would probably pay off in the long run.
>>
>> We already build with -Wundef...
>>
>
> From the gcc info page:
>
> '-Wundef'
>      Warn if an undefined identifier is evaluated in an '#if' directive.
>
> and BTW, isn't the purpose of #ifndef precisely to detect that the
> identifier is undefined ?

Yes, but it also has the typo problem above, whereas

   #if !TARGET_SUPPORTS_MTTCG

plus -Wundef would have caught that error.


r~