Include missing version header that could cause segfaults with GCC (#1508)

* Testing GCC json_t issue with version include

* flip source order

* #include <version> for __cpp_exceptions

Author: stephenberry

include/glaze/util/expected.hpp

@@ -25,6 +25,7 @@
 #pragma once
 
 #include <utility>
+#include <version>
 
 #ifndef GLZ_THROW_OR_ABORT
 #if __cpp_exceptions

tests/CMakeLists.txt

@@ -75,6 +75,7 @@ add_subdirectory(reflection)
 add_subdirectory(roundtrip)
 add_subdirectory(stencil)
 add_subdirectory(utility_formats)
+add_subdirectory(gcc_json_t_issue)
 
 # We don't run find_package_test or glaze-install_test with MSVC/Windows, because the Github action runner often chokes
 # Don't run find_package on Clang, because Linux runs with Clang try to use GCC standard library and have errors before Clang 18

tests/gcc_json_t_issue/CMakeLists.txt

@@ -0,0 +1,9 @@
+project(gcc_json_t_issue)
+
+add_executable(${PROJECT_NAME} unused.cpp ${PROJECT_NAME}.cpp)
+
+target_link_libraries(${PROJECT_NAME} PRIVATE glz_test_common)
+
+add_test(NAME ${PROJECT_NAME} COMMAND ${PROJECT_NAME})
+
+target_code_coverage(${PROJECT_NAME} AUTO ALL)

tests/gcc_json_t_issue/gcc_json_t_issue.cpp

@@ -0,0 +1,12 @@
+#include <version> // Including this header triggers the undefined behavior, even though it's not otherwise used
+#include <glaze/json.hpp>
+#include <cassert>
+
+
+int main(int argc, char const *argv[]) {
+   (void)argc;
+   (void)argv;
+    auto has_value =  glz::json_t{}.dump().has_value(); // cause SIGSEGV or  SIGABRT
+    assert(has_value);
+    return 0;
+}

tests/gcc_json_t_issue/unused.cpp

@@ -0,0 +1,5 @@
+#include <glaze/json.hpp>
+
+[[maybe_unused]] static bool unused_function() {
+    return glz::json_t{}.dump().has_value();
+}