v2: BOOST_PROCESS_V2_DISABLE_SIGNALSET does not compile with the signal-based process handle

--- a/test/v2/Jamfile.jam
+++ b/test/v2/Jamfile.jam
@@ -58,5 +58,8 @@ test-suite with_target :
     [ run process.cpp $(test_impl) : --log_level=all --catch_system_errors=no -- : target ]
     [ run windows.cpp $(test_impl) : --log_level=all --catch_system_errors=no -- : target : <build>no <target-os>windows:<build>yes <target-os>windows:<source>Advapi32 ]
     [ run ext.cpp     $(test_impl) : --log_level=all --catch_system_errors=no -- : target : <target-os>darwin:<build>no ]
+    [ run disable_signalset.cpp $(test_impl) : --log_level=all --catch_system_errors=no -- : target ]
+    [ run disable_signalset.cpp $(test_impl) : --log_level=all --catch_system_errors=no -- : target
+        : <build>no <target-os>linux:<build>yes <define>BOOST_PROCESS_V2_DISABLE_PIDFD_OPEN=1 : disable_signalset_no_pidfd ]
     ;
 
--- a/test/v2/CMakeLists.txt
+++ b/test/v2/CMakeLists.txt
@@ -34,3 +34,14 @@ endfunction()
 
 boost_process_v2_test_with_target(process)
 boost_process_v2_test_with_target(ext)
+boost_process_v2_test_with_target(disable_signalset)
+
+if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    # The signal-based process handle that macOS and the BSDs use.
+    add_executable(boost_process_v2_disable_signalset_no_pidfd disable_signalset.cpp)
+    target_link_libraries(boost_process_v2_disable_signalset_no_pidfd PUBLIC Boost::process Boost::system Boost::filesystem boost_process_v2_test_impl)
+    target_compile_definitions(boost_process_v2_disable_signalset_no_pidfd PRIVATE BOOST_PROCESS_V2_DISABLE_PIDFD_OPEN=1)
+    add_dependencies(boost_process_v2_disable_signalset_no_pidfd boost_process_v2_test_target)
+    add_test(NAME boost_process_v2_disable_signalset_no_pidfd COMMAND $<TARGET_FILE:boost_process_v2_disable_signalset_no_pidfd>
+                                                                   -- $<TARGET_FILE:boost_process_v2_test_target>)
+endif()
--- /dev/null
+++ b/test/v2/disable_signalset.cpp
@@ -0,0 +1,69 @@
+// Copyright (c) 2026 Stefan Dinkelacker
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// Disable autolinking for unit tests.
+#if !defined(BOOST_ALL_NO_LIB)
+#define BOOST_ALL_NO_LIB 1
+#endif // !defined(BOOST_ALL_NO_LIB)
+
+// An application that handles SIGCHLD itself must keep asio from installing
+// a handler for it.
+#define BOOST_PROCESS_V2_DISABLE_SIGNALSET 1
+
+#include <boost/process/v2/process.hpp>
+
+#include <boost/asio/io_context.hpp>
+#include <boost/test/unit_test.hpp>
+
+namespace bpv = boost::process::v2;
+namespace asio = boost::asio;
+
+BOOST_AUTO_TEST_SUITE(disable_signalset);
+
+BOOST_AUTO_TEST_CASE(wait)
+{
+  using boost::unit_test::framework::master_test_suite;
+  const auto pth = master_test_suite().argv[1];
+
+  asio::io_context ctx;
+  BOOST_CHECK_EQUAL(bpv::process(ctx, pth, {"exit-code", "42"}).wait(), 42);
+}
+
+BOOST_AUTO_TEST_CASE(async_wait)
+{
+  using boost::unit_test::framework::master_test_suite;
+  const auto pth = master_test_suite().argv[1];
+
+  asio::io_context ctx;
+  bpv::process proc(ctx, pth, {"exit-code", "42"});
+
+  bool called = false;
+  boost::system::error_code ec;
+  int code = -1;
+
+  proc.async_wait(
+      [&](boost::system::error_code ec_, int code_)
+      {
+        called = true;
+        ec = ec_;
+        code = code_;
+      });
+
+  ctx.run();
+  BOOST_CHECK(called);
+
+#if defined(BOOST_PROCESS_V2_WINDOWS) || defined(BOOST_PROCESS_V2_PIDFD_OPEN) \
+ || defined(BOOST_PROCESS_V2_PDFORK) || defined(BOOST_PROCESS_V2_PIPEFORK)
+  // These handles wait on a handle or descriptor, which needs no signal set.
+  BOOST_CHECK_MESSAGE(!ec, ec.message());
+  BOOST_CHECK_EQUAL(code, 42);
+#else
+  // The signal-based handle has nothing to wait on, but wait() still works.
+  BOOST_CHECK_EQUAL(ec, asio::error::operation_not_supported);
+  BOOST_CHECK_EQUAL(proc.wait(), 42);
+#endif
+}
+
+BOOST_AUTO_TEST_SUITE_END();

The CMake part follows boost_process_v2_test_with_target, which links boost_process_v2_test_impl, a target removed in 01c9a5b60f3e25f49e619df34178498e79f463e4. So on develop the CMake test build fails for all tests with a target, this one included; b2 is fine.