From ae43e8ded4f787a06c6ecaf8a3dfc5fbce20a1b0 Mon Sep 17 00:00:00 2001
From: Michael Sam <michaelsam94@users.noreply.github.com>
Date: Mon, 6 Jul 2026 13:39:03 +0300
Subject: [PATCH] Fix allocation failure during JSON destruction

Signed-off-by: Michael Sam <michaelsam94@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---
 tests/src/unit-regression2.cpp | 60 ++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/tests/src/unit-regression2.cpp b/tests/src/unit-regression2.cpp
index 79ca5a770..3548219f0 100644
--- a/tests/src/unit-regression2.cpp
+++ b/tests/src/unit-regression2.cpp
@@ -40,7 +40,9 @@ using ordered_json = nlohmann::ordered_json;
 #endif
 
 #include <cstdio>
+#include <cstdlib>
 #include <list>
+#include <new>
 #include <tuple>
 #include <type_traits>
 #include <utility>
@@ -107,6 +109,49 @@ DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")
 
 using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;
 
+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
+namespace
+{
+bool fail_next_global_allocation = false;
+
+void* checked_malloc(std::size_t size)
+{
+    if (fail_next_global_allocation)
+    {
+        fail_next_global_allocation = false;
+        throw std::bad_alloc();
+    }
+
+    if (void* const result = std::malloc(size))
+    {
+        return result;
+    }
+
+    throw std::bad_alloc();
+}
+} // namespace
+
+void* operator new (std::size_t size)
+{
+    return checked_malloc(size);
+}
+
+void* operator new[](std::size_t size)
+{
+    return checked_malloc(size);
+}
+
+void operator delete (void* ptr) noexcept
+{
+    std::free(ptr);
+}
+
+void operator delete[](void* ptr) noexcept
+{
+    std::free(ptr);
+}
+#endif
+
 /////////////////////////////////////////////////////////////////////
 // for #1647
 /////////////////////////////////////////////////////////////////////
@@ -940,4 +985,19 @@ TEST_CASE("regression test - excessive binary container size honors allow_except
     CHECK(json::from_cbor(std::vector<std::uint8_t> {0x9b, 0, 0, 0, 0, 0, 0, 0, 0x02}, true, false).is_discarded());
 }
 
+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
+TEST_CASE("regression test #5135 - destructor tolerates stack allocation failure")
+{
+    {
+        json j = json::array({json::array({1, 2}), json::object({{"key", json::array({3})}})});
+        fail_next_global_allocation = true;
+    }
+
+    const bool allocation_failure_was_injected = !fail_next_global_allocation;
+    fail_next_global_allocation = false;
+
+    CHECK(allocation_failure_was_injected);
+}
+#endif
+
 DOCTEST_CLANG_SUPPRESS_WARNING_POP