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/
> include/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
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>