We also have this in bits/floatn.h, but this seems right.

#if (defined __x86_64__                                                 \
     ? __GNUC_PREREQ (4, 3)                                             \
     : (defined __GNU__ ? __GNUC_PREREQ (4, 5) : __GNUC_PREREQ (4, 4)))
# define __HAVE_FLOAT128 1
#else
# define __HAVE_FLOAT128 0
#endif

/* Defined to 1 if __HAVE_FLOAT128 is 1 and the type is ABI-distinct


   from the default float, double and long double types in this glibc.  */
#if __HAVE_FLOAT128
# define __HAVE_DISTINCT_FLOAT128 1
#else
# define __HAVE_DISTINCT_FLOAT128 0
#endif

I think the problem is caused by HAVE_GENERIC_SELECTION defined when we are
in C++.


2017-12-04 13:18 GMT+01:00 Gábor Boskovits <boskovits@gmail.com>:

> We have this in cdefs.h:
> #if __GNUC_PREREQ (4, 9) \
>     || __glibc_clang_has_extension (c_generic_selections) \
>     || (!defined __GNUC__ && defined __STDC_VERSION__ \
>         && __STDC_VERSION__ >= 201112L)
> # define __HAVE_GENERIC_SELECTION 1
> #else
> # define __HAVE_GENERIC_SELECTION 0
> #endif
>
> This does not seem right.
>
> We should not have this defined when compiling c++.
> WDYT?
>
> 2017-12-04 13:03 GMT+01:00 Gábor Boskovits <boskovits@gmail.com>:
>
>> This minimal file reproduces the problem in icu4c 60.1 in guix
>> environment icu4c on current core-updates.
>>
>> #include <cmath>
>>
>> int main(int argc, char **argv)
>> {
>>   std::signbit(1);
>>   return 0;
>> }
>>
>> It seems, that it is some problem with cmath.h
>>
>> /gnu/store/2wzijwwgpcdb1msmn3wgq9zmrbrkpx2h-gcc-5.5.0/includ
>> e/c++/cmath:44:0
>>
>> The definition is in glibc 2.26 math.h, looks like this:
>>
>> #elif __HAVE_DISTINCT_FLOAT128
>> # if __HAVE_GENERIC_SELECTION
>> #  define __MATH_TG(TG_ARG, FUNC, ARGS)         \
>>      _Generic ((TG_ARG),                        \
>>        float: FUNC ## f ARGS,           \
>>                default: FUNC ARGS,              \
>>                long double: FUNC ## l ARGS,     \
>>                _Float128: FUNC ## f128 ARGS)
>>
>>
>>
>> 2017-12-03 23:25 GMT+01:00 Gábor Boskovits <boskovits@gmail.com>:
>>
>>> It seems, that the fix is already included in the 60.1 release for the
>>> xlocal problem. I think we can ignore that.
>>>
>>> 2017-12-03 23:20 GMT+01:00 Gábor Boskovits <boskovits@gmail.com>:
>>>
>>>> It seems, that they issued that already:
>>>> http://bugs.icu-project.org/trac/changeset/40603
>>>>
>>>> 2017-12-03 23:08 GMT+01:00 Gábor Boskovits <boskovits@gmail.com>:
>>>>
>>>>> Ok, I found this one:
>>>>> https://sourceware.org/glibc/wiki/Release/2.26#Removal_of_.2
>>>>> 7xlocale.h.27
>>>>>
>>>>> It seems, that xlocale.h should not be used as an include, and glibc
>>>>> removed that.
>>>>>
>>>>> So this is ok.
>>>>>
>>>>> The question is if this issue was addressed by icu4c, so we can just
>>>>> go to the next step, or should we do something about this.
>>>>>
>>>>>
>>>>> 2017-12-03 23:04 GMT+01:00 Gábor Boskovits <boskovits@gmail.com>:
>>>>>
>>>>>> I've found that simply reverting the update to icu4c 60 commit brings
>>>>>> up the issue you just mentioned, with missing xlocale.h.
>>>>>> So it seems, that the one you found introduced the xlocale problem,
>>>>>> while 4e080fbb0bb73e4444181599676f4e1ef5fdc2ba introduces the new
>>>>>> error.
>>>>>> I think we should deal with the one you find first, the see what's
>>>>>> with this newer one.
>>>>>>
>>>>>> We also have a long running discussion on a bug introduced by a later
>>>>>> glibc update, ee3ebf1a357bd4eb36a2fa1790a7b549cffb305a which broke a
>>>>>> lot of packages. Might these be somehow related?
>>>>>> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=29537
>>>>>>
>>>>>>
>>>>>>
>>>>>> 2017-12-03 22:46 GMT+01:00 Chris Marusich <cmmarusich@gmail.com>:
>>>>>>
>>>>>>> Gábor Boskovits <boskovits@gmail.com> writes:
>>>>>>>
>>>>>>> > Any news on this icu4c thing?
>>>>>>>
>>>>>>> After about 2 days of running git bisect, my computer has informed me
>>>>>>> that the first bad commit is 67d527e35e367c9e9e89ec01cda2ce
>>>>>>> 32cabd2d89.
>>>>>>> This is the first commit where icu4c fails to build on core-updates.
>>>>>>> The build failure at this commit is as follows:
>>>>>>>
>>>>>>> --8<---------------cut here---------------start------------->8---
>>>>>>>    g++   ...  decimfmt.cpp
>>>>>>>    g++   ...  decimalformatpattern.cpp
>>>>>>>    g++   ...  dcfmtsym.cpp
>>>>>>>    g++   ...  digitlst.cpp
>>>>>>>    g++   ...  fmtable_cnv.cpp
>>>>>>> digitlst.cpp:67:24: fatal error: xlocale.h: No such file or directory
>>>>>>> compilation terminated.
>>>>>>> *** Failed compilation command follows:
>>>>>>> ----------------------------------------------------------
>>>>>>> g++ -D_REENTRANT -DU_HAVE_ELF_H=1 -DU_HAVE_ATOMIC=1
>>>>>>> -DU_HAVE_STRTOD_L=1 -I. -I../common -DU_ATTRIBUTE_DEPRECATED=
>>>>>>> -DU_I18N_IMPLEMENTATION -O2 -W -Wall -pedantic -Wpointer-arith
>>>>>>> -Wwrite-strings -Wno-long-long --std=c++0x -c -DPIC -fPIC -o digitlst.o
>>>>>>> digitlst.cpp
>>>>>>> --- ( rebuild with "make VERBOSE=1 all" to show all parameters )
>>>>>>> --------
>>>>>>> make[1]: *** [../config/mh-linux:51: digitlst.o] Error 1
>>>>>>> make[1]: *** Waiting for unfinished jobs....
>>>>>>> make[1]: Leaving directory '/tmp/guix-build-icu4c-58.2.dr
>>>>>>> v-0/icu/source/i18n'
>>>>>>> make: *** [Makefile:143: all-recursive] Error 2
>>>>>>> phase `build' failed after 59.0 seconds
>>>>>>> builder for `/gnu/store/mdd6glhc0dg65y4wd11y0b7sbky9cwv6-icu4c-58.2.drv'
>>>>>>> failed with exit code 1
>>>>>>> @ build-failed /gnu/store/mdd6glhc0dg65y4wd11y0b7sbky9cwv6-icu4c-58.2.drv
>>>>>>> - 1 builder for `/gnu/store/mdd6glhc0dg65y4wd11y0b7sbky9cwv6-icu4c-58.2.drv'
>>>>>>> failed with exit code 1
>>>>>>> guix build: error: build failed: build of
>>>>>>> `/gnu/store/mdd6glhc0dg65y4wd11y0b7sbky9cwv6-icu4c-58.2.drv' failed
>>>>>>> --8<---------------cut here---------------end--------------->8---
>>>>>>>
>>>>>>> Note that this is NOT the same error as the one that occurs at commit
>>>>>>> d6adba786cf2ab1b26ff083928b64262281ff106 (which is the commit on
>>>>>>> core-updates from which Gábor's branch change-default-icedtea-8
>>>>>>> branch
>>>>>>> begins).  That error is:
>>>>>>>
>>>>>>> --8<---------------cut here---------------start------------->8---
>>>>>>>    g++   ...  number_decimalquantity.cpp
>>>>>>>    g++   ...  number_decimfmtprops.cpp
>>>>>>> number_decimalquantity.cpp: In member function
>>>>>>> ‘icu_60::number::impl::DecimalQuantity&
>>>>>>> icu_60::number::impl::DecimalQuantity::setToDouble(double)’:
>>>>>>> number_decimalquantity.cpp:333:9: error: ‘_Generic’ is not a member
>>>>>>> of ‘std’
>>>>>>>      if (std::signbit(n) != 0) {
>>>>>>>          ^
>>>>>>> In file included from /gnu/store/nz2m4gdvgzcrkqa4xwv
>>>>>>> 360iskh7syj7i-gcc-5.5.0/include/c++/cmath:44:0,
>>>>>>>                  from number_decimalquantity.cpp:9:
>>>>>>> number_decimalquantity.cpp:333:14: error: expected
>>>>>>> primary-expression before ‘float’
>>>>>>>      if (std::signbit(n) != 0) {
>>>>>>>               ^
>>>>>>> number_decimalquantity.cpp:333:14: error: expected
>>>>>>> primary-expression before ‘default’
>>>>>>>      if (std::signbit(n) != 0) {
>>>>>>>               ^
>>>>>>> number_decimalquantity.cpp:333:14: error: expected
>>>>>>> primary-expression before ‘long’
>>>>>>>      if (std::signbit(n) != 0) {
>>>>>>>               ^
>>>>>>> number_decimalquantity.cpp:333:14: error: expected
>>>>>>> primary-expression before ‘:’ token
>>>>>>>      if (std::signbit(n) != 0) {
>>>>>>>               ^
>>>>>>> number_decimalquantity.cpp:337:9: error: ‘__builtin_isnan’ is not a
>>>>>>> member of ‘std’
>>>>>>>      if (std::isnan(n) != 0) {
>>>>>>>          ^
>>>>>>> number_decimalquantity.cpp:337:9: note: suggested alternative:
>>>>>>> <built-in>: note:   ‘__builtin_isnan’
>>>>>>> number_decimalquantity.cpp:339:16: error: ‘__builtin_isfinite’ is
>>>>>>> not a member of ‘std’
>>>>>>>      } else if (std::isfinite(n) == 0) {
>>>>>>>                 ^
>>>>>>> number_decimalquantity.cpp:339:16: note: suggested alternative:
>>>>>>> <built-in>: note:   ‘__builtin_isfinite’
>>>>>>> *** Failed compilation command follows:
>>>>>>> ----------------------------------------------------------
>>>>>>> g++ -D_REENTRANT -DU_HAVE_ELF_H=1 -DU_HAVE_ATOMIC=1
>>>>>>> -DU_HAVE_STRTOD_L=1 -DU_HAVE_XLOCALE_H=0 -I. -I../common
>>>>>>> -DU_ATTRIBUTE_DEPRECATED= -DU_I18N_IMPLEMENTATION -O2 -W -Wall -pedantic
>>>>>>> -Wpointer-arith -Wwrite-strings -Wno-long-long -std=c++11 -c -DPIC -fPIC -o
>>>>>>> number_decimalquantity.o number_decimalquantity.cpp
>>>>>>> --- ( rebuild with "make VERBOSE=1 all" to show all parameters )
>>>>>>> --------
>>>>>>> make[1]: *** [../config/mh-linux:51: number_decimalquantity.o] Error
>>>>>>> 1
>>>>>>> make[1]: *** Waiting for unfinished jobs....
>>>>>>> make[1]: Leaving directory '/tmp/guix-build-icu4c-60.1.dr
>>>>>>> v-0/icu/source/i18n'
>>>>>>> make: *** [Makefile:149: all-recursive] Error 2
>>>>>>> phase `build' failed after 122.2 seconds
>>>>>>> builder for `/gnu/store/8s6q5cll4knh7y0wfrbjqs2dai0x4sm2-icu4c-60.1.drv'
>>>>>>> failed with exit code 1
>>>>>>> @ build-failed /gnu/store/8s6q5cll4knh7y0wfrbjqs2dai0x4sm2-icu4c-60.1.drv
>>>>>>> - 1 builder for `/gnu/store/8s6q5cll4knh7y0wfrbjqs2dai0x4sm2-icu4c-60.1.drv'
>>>>>>> failed with exit code 1
>>>>>>> guix build: error: build failed: build of
>>>>>>> `/gnu/store/8s6q5cll4knh7y0wfrbjqs2dai0x4sm2-icu4c-60.1.drv' failed
>>>>>>> --8<---------------cut here---------------end--------------->8---
>>>>>>>
>>>>>>> The fact that these errors are different suggests that more than one
>>>>>>> problem may have been introduced...
>>>>>>>
>>>>>>> I haven't tried any more recent commits on core-updates.  I am not
>>>>>>> sure
>>>>>>> what the best way is to debug this, so I would appreciate any advice
>>>>>>> anyone has.
>>>>>>>
>>>>>>> I hope that information helps.  Hopefully, together, we can untangle
>>>>>>> this!
>>>>>>>
>>>>>>> --
>>>>>>> Chris
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>