[r16-5613 Regression] FAIL: std/ranges/adaptors/93978.cc -std=gnu++26 (test for excess errors) on Linux/x86_64

[Haochen Jiang]

On Linux/x86_64,

1c9d93bfcd172c156fd0e94ea9990569bf46aeda is the first bad commit
commit 1c9d93bfcd172c156fd0e94ea9990569bf46aeda
Author: Tomasz Kamiński <tkami...@redhat.com>
Date:   Wed Nov 19 10:29:18 2025 +0100

    libstdc++: Hashing support for chrono value classes [PR110357]

caused

FAIL: std/ranges/adaptors/93978.cc  -std=gnu++26 (test for excess errors)

with GCC configured with

../../gcc/configure 
--prefix=/export/users3/haochenj/src/gcc-bisect/master/master/r16-5613/usr 
--enable-clocale=gnu --with-system-zlib --with-demangler-in-ld 
--with-fpmath=sse --enable-languages=c,c++,fortran --enable-cet --without-isl 
--enable-libmpx x86_64-linux --disable-bootstrap

To reproduce:

$ cd {build_dir}/x86_64-linux/libstdc++-v3/testsuite && make check 
RUNTESTFLAGS="conformance.exp=std/ranges/adaptors/93978.cc 
--target_board='unix{-m32}'"
$ cd {build_dir}/x86_64-linux/libstdc++-v3/testsuite && make check 
RUNTESTFLAGS="conformance.exp=std/ranges/adaptors/93978.cc 
--target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/x86_64-linux/libstdc++-v3/testsuite && make check 
RUNTESTFLAGS="conformance.exp=std/ranges/adaptors/93978.cc 
--target_board='unix{-m64}'"
$ cd {build_dir}/x86_64-linux/libstdc++-v3/testsuite && make check 
RUNTESTFLAGS="conformance.exp=std/ranges/adaptors/93978.cc 
--target_board='unix{-m64\ -march=cascadelake}'"

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