[Bug c++/82861] New: 'long double sqrtf128(long double)' conflicts with built-in declaration 'long double sqrtf128(long double)' [-Wbuiltin-declaration-mismatch]

[nsz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82861

            Bug ID: 82861
           Summary: 'long double sqrtf128(long double)' conflicts with
                    built-in declaration 'long double sqrtf128(long
                    double)' [-Wbuiltin-declaration-mismatch]
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nsz at gcc dot gnu.org
  Target Milestone: ---

on aarch64 i get nonsense warning when declaring f128 apis:

$ cat a.cc
extern "C" long double sqrtf128(long double) throw();
long double f(long double x) { return sqrtf128(x); }

$ g++ -Wall -S a.cc
a.cc:1:24: warning: declaration of 'long double sqrtf128(long double)'
conflicts with built-in declaration 'long double sqrtf128(long double)'
[-Wbuiltin-declaration-mismatch]
 extern "C" long double sqrtf128(long double) throw();
                        ^~~~~~~~

glibc math tests fail to build because of this.