From 38fbd393e8bb4943f398eaafa0173a0e2a9329f7 Mon Sep 17 00:00:00 2001
From: Nelson Vides <videsnelson@gmail.com>
Date: Thu, 9 Apr 2026 11:14:45 +0200
Subject: [PATCH 1/2] Use enif_alloc/enif_free for std::vector allocations

std::vector's default std::allocator uses malloc/free, which bypasses
BEAM memory bookkeeping. Introduce a custom enif_allocator<T> that
delegates to enif_alloc/enif_free so all NIF heap usage is visible to
erlang:memory() and crash dumps.
---
 c_src/exml.cpp | 50 ++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 42 insertions(+), 8 deletions(-)

diff --git a/c_src/exml.cpp b/c_src/exml.cpp
index 71eda1c..6b77bdf 100644
--- a/c_src/exml.cpp
+++ b/c_src/exml.cpp
@@ -17,7 +17,41 @@
 #include <thread>
 #include <vector>
 
-using ustring = std::vector<unsigned char>;
+template <typename T>
+struct enif_allocator {
+  using value_type = T;
+
+  enif_allocator() noexcept = default;
+
+  template <typename U>
+  enif_allocator(const enif_allocator<U> &) noexcept {}
+
+  T *allocate(std::size_t n) {
+    if (n > std::size_t(-1) / sizeof(T))
+      throw std::bad_alloc();
+    void *p = enif_alloc(n * sizeof(T));
+    if (!p)
+      throw std::bad_alloc();
+    return static_cast<T *>(p);
+  }
+
+  void deallocate(T *p, std::size_t) noexcept { enif_free(p); }
+};
+
+template <typename T, typename U>
+constexpr bool operator==(const enif_allocator<T> &, const enif_allocator<U> &) noexcept {
+  return true;
+}
+
+template <typename T, typename U>
+constexpr bool operator!=(const enif_allocator<T> &, const enif_allocator<U> &) noexcept {
+  return false;
+}
+
+template <typename T>
+using nif_vector = std::vector<T, enif_allocator<T>>;
+
+using ustring = nif_vector<unsigned char>;
 
 class xml_document {
 public:
@@ -86,8 +120,8 @@ struct Parser {
   std::uint64_t max_element_size = 0;
   bool infinite_stream = false;
 
-  static thread_local std::vector<unsigned char> buffer;
-  static thread_local std::vector<ERL_NIF_TERM> term_buffer;
+  static thread_local nif_vector<unsigned char> buffer;
+  static thread_local nif_vector<ERL_NIF_TERM> term_buffer;
 
   bool copy_buffer(ErlNifEnv *env, ERL_NIF_TERM buf) {
     buffer.clear();
@@ -116,8 +150,8 @@ struct Parser {
   }
 };
 
-thread_local std::vector<unsigned char> Parser::buffer;
-thread_local std::vector<ERL_NIF_TERM> Parser::term_buffer;
+thread_local nif_vector<unsigned char> Parser::buffer;
+thread_local nif_vector<ERL_NIF_TERM> Parser::term_buffer;
 
 struct ParseCtx {
   ErlNifEnv *env;
@@ -170,7 +204,7 @@ ERL_NIF_TERM merge_data_nodes(ParseCtx &ctx,
 }
 
 void append_pending_data_nodes(ParseCtx &ctx,
-                               std::vector<ERL_NIF_TERM> &children,
+                               nif_vector<ERL_NIF_TERM> &children,
                                rapidxml::xml_node<unsigned char> *node,
                                const std::size_t pending) {
   if (pending == 0)
@@ -186,7 +220,7 @@ ERL_NIF_TERM make_xmlel(ParseCtx &ctx, rapidxml::xml_node<unsigned char> *node);
 
 ERL_NIF_TERM get_children_tuple(ParseCtx &ctx,
                                 rapidxml::xml_node<unsigned char> *node) {
-  std::vector<ERL_NIF_TERM> &children = Parser::term_buffer;
+  nif_vector<ERL_NIF_TERM> &children = Parser::term_buffer;
   std::size_t begin = children.size();
 
   rapidxml::xml_node<unsigned char> *first_data_node = nullptr;
@@ -395,7 +429,7 @@ bool build_children(ErlNifEnv *env, xml_document &doc, ERL_NIF_TERM children,
 ERL_NIF_TERM node_to_binary(ErlNifEnv *env,
                             rapidxml::xml_node<unsigned char> &node,
                             int flags) {
-  static thread_local std::vector<unsigned char> print_buffer;
+  static thread_local nif_vector<unsigned char> print_buffer;
   print_buffer.clear();
 
   rapidxml::print(std::back_inserter(print_buffer), node, flags);

From 508489724e0fa67fd774b1701ad90dccdbb1a11e Mon Sep 17 00:00:00 2001
From: Nelson Vides <videsnelson@gmail.com>
Date: Wed, 13 May 2026 12:17:05 +0200
Subject: [PATCH 2/2] Apply suggestion from @kamilwaz: use
 std::numeric_limits<>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Kamil Wąż <kamilwaz@icloud.com>
---
 c_src/exml.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/c_src/exml.cpp b/c_src/exml.cpp
index 6b77bdf..e9f4dfe 100644
--- a/c_src/exml.cpp
+++ b/c_src/exml.cpp
@@ -13,6 +13,7 @@
 #include <chrono>
 #include <cstring>
 #include <iostream>
+#include <limits>
 #include <string>
 #include <thread>
 #include <vector>
@@ -27,7 +28,7 @@ struct enif_allocator {
   enif_allocator(const enif_allocator<U> &) noexcept {}
 
   T *allocate(std::size_t n) {
-    if (n > std::size_t(-1) / sizeof(T))
+    if (n > std::numeric_limits<std::size_t>::max() / sizeof(T))
       throw std::bad_alloc();
     void *p = enif_alloc(n * sizeof(T));
     if (!p)