Re: [PATCH] Preserve ::is{inf,nan}{f,l} prototypes even for C++11 and later

[Jonathan Wakely <jwakely@redhat.com>]

On 03/02/16 14:55 -0200, Adhemerval Zanella wrote:
>I will quote the email referenced:
>
>> C++11 code using isinf and isnan continues to compile after that
>> change, because the C++11 standard library provides its own versions
>> conforming to the C++11 requirements. However, the C++11 library
>> doesn't provide isinff, isinfl etc. and so code using those
>> (non-standard) functions will no longer compile if they are not
>> declared by glibc.
>
>This was not clear to me, what kind of build issue are you seeing now?

There is no issue in libstdc++ this time. The problem comes when C++11
programs try to use the glibc is{inf,nan}{f,l} functions.

>Using isinf{f,l} by including just <cmath> along with C++11? If it is the
>case please open a bugzilla (or update the original) and please commit
>the fix.

Yes, including either <cmath> or <math.h> in C++11 code and trying to
use isinf{f,l}.

>Also, do we have a testcase on libstdc++ to catch this?

No, because nothing in libstdc++ uses or cares about isinf{f,l}, they
are not standard C++ functions. Just like we don't have tests for
other glibc functions such as getwd(3) that aren't part of ISO C++.

We could add a test, but it seems like it's the wrong place for it. It
would have to be limited to only run on *-*-*gnu* targets, since those
functions might not be available elsewhere. However, if glibc doesn't
have any tests that use a C++ compiler maybe libstdc++ is the easiest
place for it.


>On 01-02-2016 14:34, Jonathan Wakely wrote:
>> On 01/02/16 17:21 +0100, Jakub Jelinek wrote:
>>> The recent changes disable not just ::is{inf,nan} prototypes that are
>>> incompatible with C++11 and later and that are defined in <cmath> or
>>> libstdc++ <math.h> wrapper, but also the ::is{inf,nan}{f,l} prototypes,
>>> that are not incompatible with C++11.  This patch adds them back.
>>
>> N.B. I also posted Jakub's patch at
>> https://sourceware.org/ml/libc-alpha/2016-02/msg00020.html with some
>> more context. The patch is the same though, so you can ignroe my
>> duplicate.
>>
>>
>>> ---
>>> math/bits/mathcalls.h | 8 ++++++--
>>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/math/bits/mathcalls.h b/math/bits/mathcalls.h
>>> index a48345d..1b82fcd 100644
>>> --- a/math/bits/mathcalls.h
>>> +++ b/math/bits/mathcalls.h
>>> @@ -196,7 +196,9 @@ __MATHDECL_1 (int,__finite,, (_Mdouble_ __value)) __attribute__ ((__const__));
>>> _Mdouble_END_NAMESPACE
>>>
>>> #ifdef __USE_MISC
>>> -# if !defined __cplusplus || __cplusplus < 201103L /* Conflicts with C++11.  */
>>> +# if (!defined __cplusplus \
>>> +      || __cplusplus < 201103L /* isinf conflicts with C++11.  */ \
>>> +      || __MATH_DECLARING_DOUBLE == 0) /* isinff or isinfl don't.  */
>>> /* Return 0 if VALUE is finite or NaN, +1 if it
>>>    is +Infinity, -1 if it is -Infinity.  */
>>> __MATHDECL_1 (int,isinf,, (_Mdouble_ __value)) __attribute__ ((__const__));
>>> @@ -232,7 +234,9 @@ __END_NAMESPACE_C99
>>> __MATHDECL_1 (int,__isnan,, (_Mdouble_ __value)) __attribute__ ((__const__));
>>>
>>> #if defined __USE_MISC || (defined __USE_XOPEN && !defined __USE_XOPEN2K)
>>> -# if !defined __cplusplus || __cplusplus < 201103L /* Conflicts with C++11.  */
>>> +# if (!defined __cplusplus \
>>> +      || __cplusplus < 201103L /* isinf conflicts with C++11.  */ \
>>> +      || __MATH_DECLARING_DOUBLE == 0) /* isinff or isinfl don't.  */
>>> /* Return nonzero if VALUE is not a number.  */
>>> __MATHDECL_1 (int,isnan,, (_Mdouble_ __value)) __attribute__ ((__const__));
>>> # endif
>>> --
>>> 2.4.3
>>>