fuzztest/internal/subprocess.cc compile fail

[Mizux]

Context, in google/or-tools when bumping abseil-cpp to 20250814.0 we had to bump fuzztest to 2025-08-05 to avoid compilation error in our bazel build BUT in cmake based build (which compile everything ie all cmake targets) I got this trace:

CMake Trace

# from ortools super build project
$ cmake -S. -Bbuild -DBUILD_DEPS=ON
$ cmake --build build --config Release
...
[ 82%] Building CXX object _deps/fuzztest-build/fuzztest/internal/CMakeFiles/fuzztest_subprocess.dir/subprocess.cc.o
In file included from /usr/local/google/home/corentinl/work/main/build/_deps/fuzztest-src/fuzztest/internal/subprocess.cc:15:
/usr/local/google/home/corentinl/work/main/build/_deps/fuzztest-src/./fuzztest/internal/subprocess.h:112:27: error: converting to ‘const std::optional<absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >’ from initializer list would use explicit constructor ‘constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]’
  112 |         environment = {{}});
      |                           ^
In file included from /usr/local/google/home/corentinl/work/main/build/_deps/fuzztest-src/./fuzztest/internal/subprocess.h:19:
/usr/include/c++/14/optional:813:9: note: ‘constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]’ declared here
  813 |         optional(in_place_t, _Args&&... __args)
      |         ^~~~~~~~
/usr/local/google/home/corentinl/work/main/build/_deps/fuzztest-src/./fuzztest/internal/subprocess.h:112:27: error: converting to ‘std::in_place_t’ from initializer list would use explicit constructor ‘constexpr std::in_place_t::in_place_t()’
  112 |         environment = {{}});
      |                           ^
In file included from /usr/include/c++/14/bits/stl_pair.h:62,
                 from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from /usr/local/google/home/corentinl/work/main/build/_deps/fuzztest-src/./fuzztest/internal/subprocess.h:18:
/usr/include/c++/14/bits/utility.h:196:14: note: ‘constexpr std::in_place_t::in_place_t()’ declared here
  196 |     explicit in_place_t() = default;
      |              ^~~~~~~~~~
/usr/local/google/home/corentinl/work/main/build/_deps/fuzztest-src/./fuzztest/internal/subprocess.h:124:54: error: converting to ‘const std::optional<absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >’ from initializer list would use explicit constructor ‘constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]’
  124 |     absl::Duration timeout = absl::InfiniteDuration());
      |                                                      ^
/usr/include/c++/14/optional:813:9: note: ‘constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]’ declared here
  813 |         optional(in_place_t, _Args&&... __args)
      |         ^~~~~~~~
/usr/local/google/home/corentinl/work/main/build/_deps/fuzztest-src/./fuzztest/internal/subprocess.h:124:54: error: converting to ‘std::in_place_t’ from initializer list would use explicit constructor ‘constexpr std::in_place_t::in_place_t()’
  124 |     absl::Duration timeout = absl::InfiniteDuration());
      |                                                      ^
/usr/include/c++/14/bits/utility.h:196:14: note: ‘constexpr std::in_place_t::in_place_t()’ declared here
  196 |     explicit in_place_t() = default;
      |              ^~~~~~~~~~
gmake[2]: *** [_deps/fuzztest-build/fuzztest/internal/CMakeFiles/fuzztest_subprocess.dir/build.make:76: _deps/fuzztest-build/fuzztest/internal/CMakeFiles/fuzztest_subprocess.dir/subprocess.cc.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:13802: _deps/fuzztest-build/fuzztest/internal/CMakeFiles/fuzztest_subprocess.dir/all] Error 2
gmake: *** [Makefile:166: all] Error 2

note: In CMake we had to apply a patch to fuzztest
https://github.com/google/or-tools/blob/main/patches/fuzztest-2025-08-05.patch

Bazel trace

I can also reproduce in our Bazel based build using the following cmd:

$ bazel build -c opt @fuzztest//fuzztest/internal:subprocess
INFO: Reading 'startup' options from /usr/local/google/home/corentinl/work/main/.bazelrc: --windows_enable_symlinks
INFO: Options provided by the client:
  Inherited 'common' options: --isatty=1 --terminal_columns=255
INFO: Reading rc options for 'build' from /usr/local/google/home/corentinl/work/main/.bazelrc:
  Inherited 'common' options: --announce_rc
INFO: Reading rc options for 'build' from /usr/local/google/home/corentinl/work/main/.bazelrc:
  'build' options: --flag_alias=with_bop=//ortools/linear_solver:with_bop --flag_alias=with_cbc=//ortools/linear_solver:with_cbc --flag_alias=with_clp=//ortools/linear_solver:with_clp --flag_alias=with_cp_sat=//ortools/linear_solver:with_cp_sat --flag_alias=with_glop=//ortools/linear_solver:with_glop --flag_alias=with_glpk=//ortools/linear_solver:with_glpk --flag_alias=with_highs=//ortools/linear_solver:with_highs --flag_alias=with_pdlp=//ortools/linear_solver:with_pdlp --flag_alias=with_scip=//ortools/linear_solver:with_scip --flag_alias=with_cplex=//ortools/linear_solver:with_cplex --flag_alias=with_xpress=//ortools/linear_solver:with_xpress --apple_platform_type=macos --enable_platform_specific_config --@rules_python//python/config_settings:python_version=3.12 --define absl=1
INFO: Found applicable config definition build:linux in file /usr/local/google/home/corentinl/work/main/.bazelrc: --cxxopt=-std=c++17 --cxxopt=-Wno-sign-compare --host_cxxopt=-std=c++17 --host_cxxopt=-Wno-sign-compare
INFO: Analyzed target @@fuzztest+//fuzztest/internal:subprocess (32 packages loaded, 160 targets configured).
ERROR: /usr/local/google/home/corentinl/.cache/bazel/_bazel_corentinl/c0610bdf3f9b7ba3884cc6008a86d79e/external/fuzztest+/fuzztest/internal/BUILD:453:11: Compiling fuzztest/internal/subprocess.cc failed: (Exit 1): gcc failed: error executing CppCompile command (from target @@fuzztest+//fuzztest/internal:subprocess) /usr/bin/gcc -U_FORTIFY_SOURCE -fstack-protector -Wall -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer -g0 -O2 '-D_FORTIFY_SOURCE=1' -DNDEBUG -ffunction-sections ... (remaining 26 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
In file included from external/fuzztest+/fuzztest/internal/subprocess.cc:15:
external/fuzztest+/./fuzztest/internal/subprocess.h:112:27: error: converting to 'const std::optional<absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >' from initializer list would use explicit constructor 'constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]'
  112 |         environment = {{}});
      |                           ^
In file included from external/fuzztest+/./fuzztest/internal/subprocess.h:19:
/usr/include/c++/14/optional:813:9: note: 'constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]' declared here
  813 |         optional(in_place_t, _Args&&... __args)
      |         ^~~~~~~~
external/fuzztest+/./fuzztest/internal/subprocess.h:112:27: error: converting to 'std::in_place_t' from initializer list would use explicit constructor 'constexpr std::in_place_t::in_place_t()'
  112 |         environment = {{}});
      |                           ^
In file included from /usr/include/c++/14/bits/stl_pair.h:62,
                 from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from external/fuzztest+/./fuzztest/internal/subprocess.h:18:
/usr/include/c++/14/bits/utility.h:196:14: note: 'constexpr std::in_place_t::in_place_t()' declared here
  196 |     explicit in_place_t() = default;
      |              ^~~~~~~~~~
external/fuzztest+/./fuzztest/internal/subprocess.h:124:54: error: converting to 'const std::optional<absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >' from initializer list would use explicit constructor 'constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]'
  124 |     absl::Duration timeout = absl::InfiniteDuration());
      |                                                      ^
/usr/include/c++/14/optional:813:9: note: 'constexpr std::optional<_Tp>::optional(std::in_place_t, _Args&& ...) [with _Args = {}; typename std::enable_if<__and_v<std::is_constructible<_Tp, _Args ...> >, bool>::type <anonymous> = false; _Tp = absl::lts_20250814::flat_hash_map<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >]' declared here
  813 |         optional(in_place_t, _Args&&... __args)
      |         ^~~~~~~~
external/fuzztest+/./fuzztest/internal/subprocess.h:124:54: error: converting to 'std::in_place_t' from initializer list would use explicit constructor 'constexpr std::in_place_t::in_place_t()'
  124 |     absl::Duration timeout = absl::InfiniteDuration());
      |                                                      ^
/usr/include/c++/14/bits/utility.h:196:14: note: 'constexpr std::in_place_t::in_place_t()' declared here
  196 |     explicit in_place_t() = default;
      |              ^~~~~~~~~~
Target @@fuzztest+//fuzztest/internal:subprocess failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 1.762s, Critical Path: 1.25s
INFO: 4 processes: 4 internal.
ERROR: Build did NOT complete successfully