Merge 8103283685 into f3dc4684b4

include/nlohmann/json.hpp

@@ -568,8 +568,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             }
             if (t == value_t::array || t == value_t::object)
             {
+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND))
+                try
+                {
+#endif
                     // flatten the current json_value to a heap-allocated stack
-                std::vector<basic_json> stack;
+                    std::vector<basic_json, allocator_type> stack;
 
                     // move the top-level items to stack
                     if (t == value_t::array)
@@ -613,6 +617,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                         // it's now safe that current_item get destructed
                         // since it doesn't have any children
                     }
+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND))
+                }
+                catch (...)     // NOLINT(bugprone-empty-catch)
+                {
+                    // Recursion avoidance has issue allocating temporary space. This may have been `std::bad_alloc`
+                    // or any other exception thrown by a custom allocator.
+                    // RAII will correctly clean up anything moved into `stack`.
+                    // Then we continue with regular recursion based destroy, which will not heap allocate.
+                }
+#endif
             }
 
             switch (t)

single_include/nlohmann/json.hpp

@@ -20567,8 +20567,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             }
             if (t == value_t::array || t == value_t::object)
             {
+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND))
+                try
+                {
+#endif
                     // flatten the current json_value to a heap-allocated stack
-                std::vector<basic_json> stack;
+                    std::vector<basic_json, allocator_type> stack;
 
                     // move the top-level items to stack
                     if (t == value_t::array)
@@ -20612,6 +20616,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                         // it's now safe that current_item get destructed
                         // since it doesn't have any children
                     }
+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND))
+                }
+                catch (...)     // NOLINT(bugprone-empty-catch)
+                {
+                    // Recursion avoidance has issue allocating temporary space. This may have been `std::bad_alloc`
+                    // or any other exception thrown by a custom allocator.
+                    // RAII will correctly clean up anything moved into `stack`.
+                    // Then we continue with regular recursion based destroy, which will not heap allocate.
+                }
+#endif
             }
 
             switch (t)

tests/src/unit-allocator.cpp

@@ -261,3 +261,58 @@ TEST_CASE("bad my_allocator::construct")
         j["test"].push_back("should not leak");
     }
 }
+
+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND))
+namespace
+{
+thread_local bool should_throw = false;
+
+struct QuotaReached : std::exception {};
+
+template<class T>
+struct allocator_controlled_throw : std::allocator<T>
+{
+    allocator_controlled_throw() = default;
+    template <class U>
+    allocator_controlled_throw(allocator_controlled_throw<U> /*unused*/) {}
+
+    template <class U>
+    struct rebind
+    {
+        using other =  allocator_controlled_throw<U>;
+    };
+
+    T* allocate(size_t n)
+    {
+        if (should_throw)
+        {
+            throw QuotaReached{};
+        }
+        return std::allocator<T>::allocate(n);
+    }
+};
+} // namespace
+
+TEST_CASE("controlled my_allocator::allocate")
+{
+    SECTION("~basic_json tolerant of internal exceptions")
+    {
+        using my_alloc_json = nlohmann::basic_json<std::map,
+              std::vector,
+              std::string,
+              bool,
+              std::int64_t,
+              std::uint64_t,
+              double,
+              allocator_controlled_throw>;
+
+        {
+            auto j = my_alloc_json{1, 2, 3, 4};
+            should_throw = true;
+            // `j` is destroyed, ~basic_json is noexcept
+            // if allocation attempted, exception thrown
+            // exception should be internally handled
+        } // should not std::terminate
+    }
+}
+#endif