configure fails on checking ino_t

[Csaba Raduly]

On Thu, Jun 8, 2017 at 12:19 AM, Eric Blake  wrote:
> On 06/07/2017 05:11 PM, Lloyd Wood via cygwin wrote:
>> Aha! just slightly later in config.log:
>>
>> configure:17957: checking for ino_t
>> configure:17957: gcc -c -g -O2  conftest.c >&5
>> configure:17957: $? = 0
>> configure:17957: gcc -c -g -O2  conftest.c >&5
>> conftest.c: In function 'main':
>> conftest.c:94:20: error: expected expression before ')' token
>> if (sizeof ((ino_t)))
>> ^
>
> This _particular_ failure is expected (you aren't showing enough of the
> config.log output).  Remember, to determine if something is a type vs.
> an expression, autoconf performs TWO compilation tests, and relies on
> the fact that sizeof(expr) and sizeof((expr)) both compile, but
> sizeof(type) compiles while sizeof((type)) must fail.  The back-to-back
> compilation is necessary to ensure that something being probed for is a
> type name rather than an arbitray expression.
>
> So just because _some_ tests fail (as expected) does not mean that this
> particular failure is where configure is messing up.

Yes, I saw this in my successful config.log (and was a bit puzzled).

Lloyd, you need to look further down in config.log, because "checking
for sizeof(ino_t)" - the one that failed for you - is after "checking
for ino_t".

Csaba
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