matplotlib · clin1234 · Aug 23, 2026 · Aug 23, 2026
diff --git a/src/_backend_agg.cpp b/src/_backend_agg.cpp
@@ -41,30 +41,27 @@ RendererAgg::RendererAgg(unsigned int width, unsigned int height, double dpi)
 
     unsigned stride(width * 4);
 
-    pixBuffer = new agg::int8u[NUMBYTES];
-    renderingBuffer.attach(pixBuffer, width, height, stride);
+    pixBuffer.reset(new agg::int8u[NUMBYTES]);
+    renderingBuffer.attach(pixBuffer.get(), width, height, stride);
     pixFmt.attach(renderingBuffer);
     rendererBase.attach(pixFmt);
     rendererBase.clear(_fill_color);
     rendererAA.attach(rendererBase);
     rendererBin.attach(rendererBase);
     hatch_size = int(dpi);
-    hatchBuffer = new agg::int8u[hatch_size * hatch_size * 4];
-    hatchRenderingBuffer.attach(hatchBuffer, hatch_size, hatch_size, hatch_size * 4);
+    hatchBuffer.reset(new agg::int8u[hatch_size * hatch_size * 4]);
+    hatchRenderingBuffer.attach(hatchBuffer.get(), hatch_size, hatch_size, hatch_size * 4);
 }
 
 RendererAgg::~RendererAgg()
 {
-    delete[] hatchBuffer;
-    delete[] alphaBuffer;
-    delete[] pixBuffer;
 }
 
 void RendererAgg::create_alpha_buffers()
 {
     if (!alphaBuffer) {
-        alphaBuffer = new agg::int8u[width * height];
-        alphaMaskRenderingBuffer.attach(alphaBuffer, width, height, width);
+        alphaBuffer.reset(new agg::int8u[width * height]);
+        alphaMaskRenderingBuffer.attach(alphaBuffer.get(), width, height, width);
         rendererBaseAlphaMask.attach(pixfmtAlphaMask);
         rendererAlphaMask.attach(rendererBaseAlphaMask);
     }

diff --git a/src/_backend_agg.h b/src/_backend_agg.h
@@ -11,6 +11,7 @@
 #include <cmath>
 #include <algorithm>
 #include <functional>
+#include <memory>
 #include <optional>
 #include <vector>
 
@@ -206,10 +207,10 @@ class RendererAgg
     double dpi;
     size_t NUMBYTES; // the number of bytes in buffer
 
-    agg::int8u *pixBuffer;
+    std::unique_ptr<agg::int8u[]> pixBuffer;
     agg::rendering_buffer renderingBuffer;
 
-    agg::int8u *alphaBuffer;
+    std::unique_ptr<agg::int8u[]> alphaBuffer;
     agg::rendering_buffer alphaMaskRenderingBuffer;
     alpha_mask_type alphaMask;
     agg::pixfmt_gray8 pixfmtAlphaMask;
@@ -229,7 +230,7 @@ class RendererAgg
     agg::trans_affine lastclippath_transform;
 
     size_t hatch_size;
-    agg::int8u *hatchBuffer;
+    std::unique_ptr<agg::int8u[]> hatchBuffer;
     agg::rendering_buffer hatchRenderingBuffer;
 
     agg::rgba _fill_color;

diff --git a/src/_backend_agg_wrapper.cpp b/src/_backend_agg_wrapper.cpp
@@ -243,7 +243,7 @@ PYBIND11_MODULE(_backend_agg, m, py::mod_gil_not_used())
                 4,
                 1
             };
-            return py::buffer_info(renderer->pixBuffer, shape, strides);
+            return py::buffer_info(renderer->pixBuffer.get(), shape, strides);
         });
 
     py::classh<BufferRegion>(m, "BufferRegion", py::buffer_protocol())

diff --git a/src/_c_internal_utils.cpp b/src/_c_internal_utils.cpp
@@ -164,7 +164,13 @@ mpl_GetCurrentProcessExplicitAppUserModelID(void)
         PyErr_SetFromWindowsErr(hr);
         throw py::error_already_set();
     }
-    auto py_appid = py::cast(appid);
+    py::object py_appid;
+    try {
+        py_appid = py::cast(appid);
+    } catch (...) {
+        CoTaskMemFree(appid);  // don't leak the COM-allocated string on error
+        throw;
+    }
     CoTaskMemFree(appid);
     return py_appid;
 #else

diff --git a/src/_qhull_wrapper.cpp b/src/_qhull_wrapper.cpp
@@ -133,6 +133,10 @@ class QhullInfo {
         }
     }
 
+    // Uniquely owns qh and error_file; forbid copying (Rule of Three).
+    QhullInfo(const QhullInfo&) = delete;
+    QhullInfo& operator=(const QhullInfo&) = delete;
+
 private:
     FILE* error_file;
     qhT* qh;

diff --git a/src/ft2font.cpp b/src/ft2font.cpp
@@ -7,6 +7,8 @@
 #include <cstdio>
 #include <iterator>
 #include <map>
+#include <mutex>
+#include <new>
 #include <set>
 #include <stdexcept>
 #include <string>
@@ -17,8 +19,13 @@
 #endif
 
 FT2Image::FT2Image(unsigned long width, unsigned long height)
-    : m_buffer((unsigned char *)calloc(width * height, 1)), m_width(width), m_height(height)
+    // calloc(width, height) performs the width*height overflow check internally
+    // and returns nullptr on overflow or allocation failure.
+    : m_buffer((unsigned char *)calloc(width, height)), m_width(width), m_height(height)
 {
+    if (!m_buffer && width != 0 && height != 0) {
+        throw std::bad_alloc();
+    }
 }
 
 FT2Image::~FT2Image()

diff --git a/src/ft2font_wrapper.cpp b/src/ft2font_wrapper.cpp
@@ -10,6 +10,8 @@
 #include "ft2font.h"
 #include "mplutils.h"
 
+#include <memory>
+#include <mutex>
 #include <set>
 #include <sstream>
 #include <unordered_map>
@@ -291,6 +293,18 @@ class PyFT2Font final : public FT2Font
     py::list fallbacks;
     bool from_path = false;
 
+    // Serializes this object's mutating Python-facing methods so that concurrent
+    // calls on the SAME FT2Font (under free-threading / py::mod_gil_not_used)
+    // cannot corrupt its FreeType glyph slot, glyph list or image buffer. It is
+    // taken ONLY at the wrapper boundary -- never inside FT2Font's C++ methods,
+    // which also run during construction and fallback recursion -- so a single
+    // lock is held per top-level call and it never nests (deadlock-free by
+    // construction). Recursive to tolerate re-entry via Python callbacks such as
+    // ft_glyph_warn(). Contract: one FT2Font (together with its fallback graph)
+    // is used by a single thread at a time; matplotlib enforces this via the
+    // thread-keyed cache in font_manager._get_font.
+    std::recursive_mutex mutex;
+
     ~PyFT2Font()
     {
         // Because destructors are called from subclass up to base class, we need to
@@ -434,7 +448,9 @@ PyFT2Font_init(FT_Library ft2Library, py::object filename,
                   std::back_inserter(fallback_fonts));
     }
 
-    auto self = new PyFT2Font(fallback_fonts, warn_if_used);
+    // Own the object locally so it is released if any step below throws (e.g. a
+    // corrupt font makes self->open() fail); pybind11 adopts it only on success.
+    auto self = std::make_unique<PyFT2Font>(fallback_fonts, warn_if_used);
     self->set_kerning_factor(*kerning_factor);
 
     if (fallback_list) {
@@ -452,7 +468,7 @@ PyFT2Font_init(FT_Library ft2Library, py::object filename,
     // file we opened, and nullptr for a caller-owned one.
     auto stream_font_via_python = [&](FT_Stream_CloseFunc close) {
         self->stream.size = 0x7fffffff;  // Unknown size.
-        self->stream.descriptor.pointer = self;
+        self->stream.descriptor.pointer = self.get();
         self->stream.read = &read_from_file_callback;
         self->stream.close = close;
         open_args.flags = FT_OPEN_STREAM;
@@ -516,7 +532,7 @@ PyFT2Font_init(FT_Library ft2Library, py::object filename,
 
     self->open(ft2Library, open_args, face_index);
 
-    return self;
+    return self.release();
 }
 
 static py::object
@@ -656,6 +672,7 @@ PyFT2Font_set_text(PyFT2Font *self, std::u32string_view text, double angle = 0.0
                    std::optional<std::vector<std::string>> features = std::nullopt,
                    std::variant<FT2Font::LanguageType, std::string> languages_or_str = nullptr)
 {
+    std::scoped_lock lock{self->mutex};
     std::vector<double> xys;
     FT2Font::LanguageType languages = std::visit(overloaded {
         [](FT2Font::LanguageType languages) {
@@ -709,6 +726,7 @@ static PyGlyph *
 PyFT2Font_load_char(PyFT2Font *self, long charcode,
                     LoadFlags flags = LoadFlags::FORCE_AUTOHINT)
 {
+    std::scoped_lock lock{self->mutex};
     bool fallback = true;
     FT2Font *ft_object = nullptr;
 
@@ -747,6 +765,7 @@ static PyGlyph *
 PyFT2Font_load_glyph(PyFT2Font *self, FT_UInt glyph_index,
                      LoadFlags flags = LoadFlags::FORCE_AUTOHINT)
 {
+    std::scoped_lock lock{self->mutex};
     self->load_glyph(glyph_index, static_cast<FT_Int32>(flags));
 
     return PyGlyph_from_FT2Font(self);
@@ -849,6 +868,7 @@ PyFT2Font_draw_glyph_to_bitmap(PyFT2Font *self, py::buffer &image,
                                int xd, int yd,
                                PyGlyph *glyph, bool antialiased = true)
 {
+    std::scoped_lock lock{self->mutex};
     self->draw_glyph_to_bitmap(
         py::array_t<uint8_t, py::array::c_style>{image},
         xd, yd, glyph->glyphInd, antialiased);
@@ -1373,6 +1393,7 @@ PyFT2Font_layout(PyFT2Font *self, std::u32string text, LoadFlags flags,
                  std::optional<std::vector<std::string>> features = std::nullopt,
                  std::variant<FT2Font::LanguageType, std::string> languages_or_str = nullptr)
 {
+    std::scoped_lock lock{self->mutex};
     const auto load_flags = static_cast<FT_Int32>(flags);
 
     FT2Font::LanguageType languages = std::visit(overloaded {
@@ -1615,7 +1636,12 @@ PYBIND11_MODULE(ft2font, m, py::mod_gil_not_used())
              "face_index"_a=0, "_fallback_list"_a=py::none(),
              "_kerning_factor"_a=py::none(), "_warn_if_used"_a=false,
              PyFT2Font_init__doc__)
-        .def("clear", &PyFT2Font::clear, PyFT2Font_clear__doc__)
+        .def("clear",
+             [](PyFT2Font& self) {
+                 std::scoped_lock lock{self.mutex};
+                 self.clear();
+             },
+             PyFT2Font_clear__doc__)
         .def("set_size", &PyFT2Font::set_size, "ptsize"_a, "dpi"_a,
              PyFT2Font_set_size__doc__)
         .def("_set_transform", &PyFT2Font::_set_transform, "matrix"_a, "delta"_a,
@@ -1646,7 +1672,11 @@ PYBIND11_MODULE(ft2font, m, py::mod_gil_not_used())
         .def("get_bitmap_offset", &PyFT2Font::get_bitmap_offset,
              PyFT2Font_get_bitmap_offset__doc__)
         .def("get_descent", &PyFT2Font::get_descent, PyFT2Font_get_descent__doc__)
-        .def("draw_glyphs_to_bitmap", &PyFT2Font::draw_glyphs_to_bitmap,
+        .def("draw_glyphs_to_bitmap",
+             [](PyFT2Font& self, bool antialiased) {
+                 std::scoped_lock lock{self.mutex};
+                 self.draw_glyphs_to_bitmap(antialiased);
+             },
              py::kw_only(), "antialiased"_a=true,
              PyFT2Font_draw_glyphs_to_bitmap__doc__)
         .def("draw_glyph_to_bitmap", &PyFT2Font_draw_glyph_to_bitmap,
-Original file line number
+Diff line change
@@ Expand Up / @@ -243,7 +243,7 @@ PYBIND11_MODULE(_backend_agg, m, py::mod_gil_not_used()) @@
 ,
                 };
-                return py::buffer_info(renderer->pixBuffer, shape, strides);
+                return py::buffer_info(renderer->pixBuffer.get(), shape, strides);
             });
         py::classh<BufferRegion>(m, "BufferRegion", py::buffer_protocol())
@@ Expand Down @@