[Bug libgdiagnostics/121260] New: [16 Regression] Build failure on --enable-checking=release: gcc/diagnostics/changes.cc:900:2: error: expected '}' at end of input

[slyfox at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121260

            Bug ID: 121260
           Summary: [16 Regression] Build failure on
                    --enable-checking=release:
                    gcc/diagnostics/changes.cc:900:2: error: expected '}'
                    at end of input
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgdiagnostics
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: slyfox at gcc dot gnu.org
  Target Milestone: ---

Looks like gcc/diagnostics/changes.cc has imbalanced `namespace {}` brackets
when `CHECKING_P` is not defined:

$ ~/dev/git/gcc/configure --enable-checking=release --disable-multilib
$ make
...
g++ -std=c++14  -fno-PIE -c   -g -DIN_GCC    -fno-exceptions -fno-rtti
-fasynchronous-unwind-tables -W -Wall -Wno-error=narrowing -Wwrite-strings
-Wcast-qual -Wno-format   -DHAVE_CONFIG_H -fno-PIE -I. -Idiagnostics
-I/home/slyfox/dev/git/gcc/gcc -I/home/slyfox/dev/git/gcc/gcc/diagnostics
-I/home/slyfox/dev/git/gcc/gcc/../include 
-I/home/slyfox/dev/git/gcc/gcc/../libcpp/include
-I/home/slyfox/dev/git/gcc/gcc/../libcody 
-I/home/slyfox/dev/git/gcc/gcc/../libdecnumber
-I/home/slyfox/dev/git/gcc/gcc/../libdecnumber/bid -I../libdecnumber
-I/home/slyfox/dev/git/gcc/gcc/../libbacktrace   -o diagnostics/changes.o -MT
diagnostics/changes.o -MMD -MP -MF diagnostics/.deps/changes.TPo
/home/slyfox/dev/git/gcc/gcc/diagnostics/changes.cc
/home/slyfox/dev/git/gcc/gcc/diagnostics/changes.cc:900:2: error: expected '}'
at end of input
  900 | }
      |  ^