[r17-6185 Regression] FAIL: g++.dg/contracts/cpp26/non-const1.C -std=c++14 (test for excess errors) on Linux/x86_64

[Haochen Jiang]

On Linux/x86_64,

40e768675470b635d6ace326a3cb88dd32e19431 is the first bad commit
commit 40e768675470b635d6ace326a3cb88dd32e19431
Author: Jason Merrill <ja...@redhat.com>
Date:   Thu Nov 12 12:33:59 2026 -0500

    c++: fix testcase

caused

FAIL: g++.dg/contracts/cpp26/non-const1.C  -std=c++14 (test for excess errors)
FAIL: g++.dg/contracts/cpp26/non-const1.C  -std=c++20 (test for excess errors)

with GCC configured with

../../gcc/configure 
--prefix=/export/users3/haochenj/src/gcc-bisect/master/master/r17-6185/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}/gcc && make check 
RUNTESTFLAGS="dg.exp=g++.dg/contracts/cpp26/non-const1.C 
--target_board='unix{-m32}'"
$ cd {build_dir}/gcc && make check 
RUNTESTFLAGS="dg.exp=g++.dg/contracts/cpp26/non-const1.C 
--target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check 
RUNTESTFLAGS="dg.exp=g++.dg/contracts/cpp26/non-const1.C 
--target_board='unix{-m64}'"
$ cd {build_dir}/gcc && make check 
RUNTESTFLAGS="dg.exp=g++.dg/contracts/cpp26/non-const1.C 
--target_board='unix{-m64\ -march=cascadelake}'"

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