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Subject:	Re: should scanf be getting built supporting hexadecimal float
To:	cygwin AT cygwin DOT com
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	<189e0004-0cee-0e1d-2c2f-0acd7d8ca2fb AT SystematicSw DOT ab DOT ca>
From:	Brian Inglis <Brian DOT Inglis AT SystematicSw DOT ab DOT ca>
Organization:	Systematic Software
Message-ID:	<91cf4bdd-9a97-6d6b-73af-01e891c22182@SystematicSw.ab.ca>
Date:	Mon, 19 Apr 2021 09:17:48 -0600
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On 2021-04-19 09:07, Brian Inglis wrote:
> On 2021-04-18 22:09, Keith Thompson via Cygwin wrote:
>> The *scanf() functions don't handle hexadecimal floating-point input
>> (for example "0x1p+0" representing 1.0).
>> On Cygwin, the output (compiled with gcc or clang) is:
>> sscanf returned 1, x = 0 (expected 1), FAILED
>> On Ubuntu, the output is:
>> sscanf returned 1, x = 1, PASSED
>> Looking through the newlib sources (git://sourceware.org/git/newlib-cygwin.git),
>> this might be related to the _WANT_IO_C99_FORMATS macro, but I haven't
>> looked into
>> the details.
>> The test case passes on Cygwin when compiled with i686-w64-mingw32-gcc
>> or x86_64-w64-mingw32-gcc.

> This seems like an oversight as gdtoa-gethex.c was added about 2006 and scanf 
> and strtod support it.
> See augmented STC with strtod added attached:
> 
> $ gcc -o hexfloat-scanf-test{,.c}
> $ ./hexfloat-scanf-test
> sscanf returned 2, unscanned 'x1p+0', x = 0 (expected 1), FAILED
> strtod unscanned '', x = 1, PASSED

Should the Cygwin newlib build be enabling hex float support?

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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