Having problems generating a code coverage report

Hi hackers,

Recently I tried to build a code coverage report according to the
documentation [1]. When using the following command:

```
time sh -c 'git clean -dfx && meson setup --buildtype debug
-DPG_TEST_EXTRA="kerberos ldap ssl" -Db_coverage=true -Dldap=disabled
-Dssl=openssl -Dcassert=true -Dtap_tests=enabled
-Dprefix=/home/eax/pginstall build && ninja -C build &&
PG_TEST_EXTRA=1 meson test -C build && ninja -C build coverage-html'
```

... I get:

```
geninfo: ERROR: Unexpected negative count '-3' for
/home/eax/projects/c/postgresql/src/port/snprintf.c:532.
Perhaps you need to compile with '-fprofile-update=atomic
(use "geninfo --ignore-errors negative ..." to bypass this error)
Traceback (most recent call last):
File "/usr/bin/meson", line 40, in <module>
sys.exit(mesonmain.main())
^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/mesonmain.py", line
294, in main
return run(sys.argv[1:], launcher)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/mesonmain.py", line
282, in run
return run_script_command(args[1], args[2:])
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/mesonmain.py", line
223, in run_script_command
return module.run(script_args)
^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/scripts/coverage.py",
line 206, in run
return coverage(options.outputs, options.source_root,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/scripts/coverage.py",
line 123, in coverage
subprocess.check_call([lcov_exe,
File "/usr/lib/python3.12/subprocess.py", line 413, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['lcov', '--directory',
'/home/eax/projects/c/postgresql/build', '--capture', '--output-file',
'/home/eax/projects/c/postgresql/build/meson-logs/coverage.info.run',
'--no-checksum', '--rc', 'branch_coverage=1']' returned non-zero exit
status 1.
ninja: build stopped: subcommand failed.
```

If I add -fprofile-update=atomic as suggested:

```
time CFLAGS="-fprofile-update=atomic"
CXXFLAGS="-fprofile-update=atomic" sh -c 'git clean -dfx && meson
setup --buildtype debug -DPG_TEST_EXTRA="kerberos ldap ssl"
-Db_coverage=true -Dldap=disabled -Dssl=openssl -Dcassert=true
-Dtap_tests=enabled -Dprefix=/home/eax/pginstall build && ninja -C
build && PG_TEST_EXTRA=1 meson test -C build && ninja -C build
coverage-html'
```

... I get:

```
genhtml: ERROR: duplicate merge record src/include/catalog
Traceback (most recent call last):
File "/usr/bin/meson", line 40, in <module>
sys.exit(mesonmain.main())
^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/mesonmain.py", line
294, in main
return run(sys.argv[1:], launcher)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/mesonmain.py", line
282, in run
return run_script_command(args[1], args[2:])
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/mesonmain.py", line
223, in run_script_command
return module.run(script_args)
^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/scripts/coverage.py",
line 206, in run
return coverage(options.outputs, options.source_root,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/mesonbuild/scripts/coverage.py",
line 150, in coverage
subprocess.check_call([genhtml_exe,
File "/usr/lib/python3.12/subprocess.py", line 413, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['genhtml', '--prefix',
'/home/eax/projects/c/postgresql/build', '--prefix',
'/home/eax/projects/c/postgresql', '--output-directory',
'/home/eax/projects/c/postgresql/build/meson-logs/coveragereport',
'--title', 'Code coverage', '--legend', '--show-details',
'--branch-coverage',
'/home/eax/projects/c/postgresql/build/meson-logs/coverage.info']'
returned non-zero exit status 1.
ninja: build stopped: subcommand failed.
```

I'm using Xubuntu 24.04 LTS and my lcov version is:

```
$ lcov --version
lcov: LCOV version 2.0-1
```

I tried using Autotools with the same results. Pretty confident it
worked before. I'm wondering if anyone else experienced this lately
and/or knows a workaround.

[1]: https://www.postgresql.org/docs/current/regress-coverage.html

--
Best regards,
Aleksander Alekseev