Fix MSVC /W4 unreachable-code error in v3 C dtoa

When TG3JSON_USE_STDLIB_FPCONV is enabled (auto-selected on MSVC), the
stdlib float-formatting block in tg3json__dtoa_c() always returns, making
the manual long-double formatting fallback dead code. MSVC /W4 /WX turned
the resulting C4702 (unreachable code) into a build error.

Make the manual fallback an #else branch of the stdlib path so neither
configuration contains unreachable code, and guard the fallback-only
locals and helpers (tg3json__utoa, tg3json__write_exp,
tg3json__format_decimal_digits) under !TG3JSON_USE_STDLIB_FPCONV to avoid
unused-function/variable warnings on the stdlib path.

Verified with gcc -Wall -Wextra -Werror across all v3 C test sources in
both fpconv configurations, plus runtime runs of tester_v3_json_c.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/instructions/copilot-instructions.md

@@ -1,92 +0,0 @@
-# Copilot Review Instructions for TinyGLTF
-
-This document provides guidelines for reviewing code changes in the TinyGLTF repository.
-
-## Memory Safety
-
-- **Buffer Overflows**: Check for proper bounds checking when accessing arrays, vectors, and buffers. Verify that buffer sizes are validated before read/write operations.
-- **Null Pointer Dereferences**: Ensure all pointers are checked for null before dereferencing, especially when handling optional glTF fields.
-- **Memory Leaks**: Verify proper resource management, including RAII patterns for file handles, image data, and dynamically allocated memory.
-- **Use-After-Free**: Check for proper lifetime management of objects, especially when dealing with callbacks and asynchronous operations.
-
-## Error Handling
-
-- **File I/O**: Verify that all file operations have proper error checking and meaningful error messages.
-- **JSON Parsing**: Ensure JSON parsing errors are caught and reported with helpful context about the location and nature of the error.
-- **Resource Loading**: Check that failures in loading images, buffers, and other resources are properly handled and don't cause crashes.
-- **Error Propagation**: Verify that errors are properly propagated through the call stack with appropriate error messages.
-
-## glTF 2.0 Specification Compliance
-
-- **Required Fields**: Ensure all required glTF fields are validated and present.
-- **Data Types**: Verify that data types match the glTF specification (e.g., component types, accessor types).
-- **Constraints**: Check that glTF constraints are enforced (e.g., valid ranges for enums, buffer stride requirements).
-- **Extensions**: Verify proper handling of glTF extensions and that unknown extensions are handled gracefully.
-- **Validation**: Ensure new features align with the glTF 2.0 specification from the Khronos Group.
-
-## Cross-Platform Compatibility
-
-- **Windows**: Check for proper handling of Windows-specific issues (path separators, line endings, file operations).
-- **Linux**: Verify compatibility with various Linux distributions and compilers (GCC, Clang).
-- **macOS**: Ensure macOS-specific considerations are addressed (case-sensitive filesystems, Clang compatibility).
-- **Mobile Platforms**: Consider Android and iOS compatibility where applicable.
-- **Endianness**: Verify proper handling of byte order when reading binary data.
-- **Compiler Compatibility**: Ensure code compiles with C++11 standard and supported compilers (MSVC, GCC, Clang).
-
-## Edge Cases in glTF Parsing
-
-- **Empty/Minimal Files**: Verify handling of minimal valid glTF files.
-- **Large Files**: Check for proper handling of large glTF files and buffers without memory exhaustion.
-- **Malformed Data**: Ensure graceful handling of malformed or invalid glTF data.
-- **Missing Optional Fields**: Verify correct behavior when optional glTF fields are absent.
-- **Edge Values**: Check handling of boundary values (e.g., maximum buffer sizes, extreme floating-point values).
-- **Base64 Encoding**: Verify proper handling of base64-encoded data URIs and invalid encodings.
-
-## Backwards Compatibility
-
-- **API Changes**: Ensure public API changes maintain backwards compatibility or are properly deprecated.
-- **Breaking Changes**: Flag any breaking changes for major version updates and document migration paths.
-- **Binary Compatibility**: Consider ABI stability for header-only library changes.
-- **Default Behavior**: Verify that default behavior of existing functionality remains unchanged.
-
-## Performance Considerations
-
-- **Parsing Performance**: Check for unnecessary copies, redundant allocations, and inefficient algorithms in parsing logic.
-- **Memory Usage**: Verify efficient memory usage, especially when loading large glTF files.
-- **I/O Operations**: Ensure efficient file reading and minimize unnecessary disk access.
-- **String Operations**: Check for efficient string handling (use of string_view, move semantics).
-- **STL Usage**: Verify appropriate use of STL containers and algorithms.
-
-## Documentation
-
-- **Public API**: Ensure all public functions, classes, and methods have clear documentation comments.
-- **Parameters**: Verify that function parameters are documented, including expected ranges and constraints.
-- **Return Values**: Document return values and possible error conditions.
-- **Examples**: Check that complex features include usage examples.
-- **Changelog**: Verify that significant changes are documented in release notes or changelog.
-
-## Testing
-
-- **Test Coverage**: Ensure new features include appropriate unit tests or integration tests.
-- **Edge Cases**: Verify that tests cover edge cases and error conditions.
-- **Cross-Platform Tests**: Check that tests run on all supported platforms.
-- **Regression Tests**: Ensure bug fixes include regression tests to prevent recurrence.
-- **Sample Files**: Verify that changes are tested with various valid and invalid glTF sample files.
-
-## Code Style Consistency
-
-- **Header-Only Pattern**: Maintain the header-only library structure.
-- **Naming Conventions**: Follow existing naming conventions (CamelCase for types, snake_case for functions where applicable).
-- **Formatting**: Adhere to the existing code formatting style (check `.clang-format` if available).
-- **Include Guards**: Verify proper include guards and header organization.
-- **Namespace Usage**: Ensure proper use of the `tinygltf` namespace.
-- **Comments**: Maintain consistent comment style with existing code.
-- **C++11 Compliance**: Verify that code uses C++11 features appropriately and doesn't require newer standards unless specified.
-
-## Additional Considerations
-
-- **Third-Party Dependencies**: Minimize new dependencies; prefer existing dependencies (json.hpp, stb_image).
-- **Warnings**: Ensure code compiles without warnings on supported compilers.
-- **const Correctness**: Verify proper use of const for parameters and methods.
-- **RAII**: Prefer RAII patterns for resource management over manual cleanup.
-- **noexcept**: Use noexcept appropriately for move constructors and move assignment operators.

.github/workflows/c-cpp.yml

@@ -66,10 +66,12 @@ jobs:
           mkdir build
           cd build
           cmake --help
-          cmake -G "Visual Studio 17 2022" -A x64 -DTINYGLTF_BUILD_LOADER_EXAMPLE=On -DTINYGLTF_BUILD_GL_EXAMPLES=Off -DTINYGLTF_BUILD_VALIDATOR_EXAMPLE=On ..
+          cmake -G "Visual Studio 17 2022" -A x64 -DTINYGLTF_BUILD_LOADER_EXAMPLE=On -DTINYGLTF_BUILD_GL_EXAMPLES=Off -DTINYGLTF_BUILD_VALIDATOR_EXAMPLE=On -DTINYGLTF_BUILD_TESTS=ON ..
           cd ..
       - name: Build
         run: cmake --build build --config Release
+      - name: Run tests
+        run: ctest --test-dir build -C Release --output-on-failure
 
 
   build-linux:
@@ -109,6 +111,12 @@ jobs:
         cc -I../ -std=c11 -g -O0 -DTINYGLTF3_ENABLE_FS \
            -o tester_v3_c_v1port tester_v3_c_v1port.c ../tiny_gltf_v3.c
         ./tester_v3_c_v1port
+        cc -I../ -std=c11 -g -O0 \
+           -o tester_v3_json_c tester_v3_json_c.c
+        ./tester_v3_json_c
+        cc -I../ -std=c11 -ffreestanding -g -O0 \
+           -o tester_v3_freestanding tester_v3_freestanding.c
+        ./tester_v3_freestanding
         cd ..
 
 
@@ -177,4 +185,3 @@ jobs:
 
             git clone https://github.com/Tencent/rapidjson
             clang++ -DTINYGLTF_USE_RAPIDJSON -I./rapidjson/include/rapidjson -std=c++11 -g -O0 -o loader_example loader_example.cc
-

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Configure
-        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON
+        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DTINYGLTF_BUILD_TESTS=ON
 
       - name: Build
         run: cmake --build build
@@ -53,7 +53,7 @@ jobs:
 
       - name: Configure
         run: |
-          cmake -B build -DCMAKE_C_COMPILER=clang-21 -DCMAKE_CXX_COMPILER=clang++-21 -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON
+          cmake -B build -DCMAKE_C_COMPILER=clang-21 -DCMAKE_CXX_COMPILER=clang++-21 -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DTINYGLTF_BUILD_TESTS=ON
 
       - name: Build
         run: cmake --build build
@@ -74,7 +74,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Configure
-        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON
+        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DTINYGLTF_BUILD_TESTS=ON
 
       - name: Build
         run: cmake --build build
@@ -94,7 +94,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Configure
-        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON
+        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DTINYGLTF_BUILD_TESTS=ON
 
       - name: Build
         run: cmake --build build
@@ -117,7 +117,7 @@ jobs:
         run: |
           mkdir build
           cd build
-          cmake -G "Visual Studio 17 2022" -A x64 -DTINYGLTF_BUILD_LOADER_EXAMPLE=On -DTINYGLTF_BUILD_GL_EXAMPLES=Off -DTINYGLTF_BUILD_VALIDATOR_EXAMPLE=Off ..
+          cmake -G "Visual Studio 17 2022" -A x64 -DTINYGLTF_BUILD_LOADER_EXAMPLE=On -DTINYGLTF_BUILD_GL_EXAMPLES=Off -DTINYGLTF_BUILD_VALIDATOR_EXAMPLE=Off -DTINYGLTF_BUILD_TESTS=ON ..
 
       - name: Build
         run: cmake --build build --config Release
@@ -141,7 +141,7 @@ jobs:
         run: |
           mkdir build
           cd build
-          cmake -G "Visual Studio 17 2022" -A Win32 -DTINYGLTF_BUILD_LOADER_EXAMPLE=On -DTINYGLTF_BUILD_GL_EXAMPLES=Off -DTINYGLTF_BUILD_VALIDATOR_EXAMPLE=Off ..
+          cmake -G "Visual Studio 17 2022" -A Win32 -DTINYGLTF_BUILD_LOADER_EXAMPLE=On -DTINYGLTF_BUILD_GL_EXAMPLES=Off -DTINYGLTF_BUILD_VALIDATOR_EXAMPLE=Off -DTINYGLTF_BUILD_TESTS=ON ..
 
       - name: Build
         run: cmake --build build --config Release
@@ -189,7 +189,7 @@ jobs:
 
       - name: Build with CMake
         run: |
-          cmake -G"Ninja" -S . -B build
+          cmake -G"Ninja" -S . -B build -DTINYGLTF_BUILD_TESTS=ON
           cmake --build build
 
       - name: Run loader_example
@@ -249,7 +249,7 @@ jobs:
       - name: Build with CMake Header-Only
         run: |
           mkdir build
-          cmake -B build -DTINYGLTF_HEADER_ONLY=ON -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON
+          cmake -B build -DTINYGLTF_HEADER_ONLY=ON -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DTINYGLTF_BUILD_TESTS=ON
           cmake --build build
 
       - name: Run loader_example
@@ -259,6 +259,30 @@ jobs:
       - name: Run tests
         run: ctest --test-dir build --output-on-failure
 
+  # v3 C tests through Meson on the primary desktop platforms.
+  v3-c-meson:
+    runs-on: ${{ matrix.os }}
+    name: v3 C Meson (${{ matrix.os }})
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Install Meson
+        run: python -m pip install meson ninja
+
+      - name: Configure
+        run: meson setup build-meson -Dtests=true
+
+      - name: Build
+        run: meson compile -C build-meson
+
+      - name: Run v3 C tests
+        run: meson test -C build-meson --print-errorlogs
+
   # Special Configuration: RapidJSON Backend
   linux-rapidjson:
     runs-on: ubuntu-latest
@@ -273,7 +297,7 @@ jobs:
 
       - name: Configure
         run: |
-          cmake -B build -DTINYGLTF_USE_RAPIDJSON=ON -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DCMAKE_PREFIX_PATH=$PWD/rapidjson
+          cmake -B build -DTINYGLTF_USE_RAPIDJSON=ON -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DTINYGLTF_BUILD_TESTS=ON -DCMAKE_PREFIX_PATH=$PWD/rapidjson
 
       - name: Build
         run: cmake --build build

.github/workflows/codeql-analysis.yml

@@ -1,72 +0,0 @@
-# For most projects, this workflow file will not need changing; you simply need
-# to commit it to your repository.
-#
-# You may wish to alter this file to override the set of languages analyzed,
-# or to provide custom queries or build logic.
-#
-# ******** NOTE ********
-# We have attempted to detect the languages in your repository. Please check
-# the `language` matrix defined below to confirm you have the correct set of
-# supported CodeQL languages.
-#
-name: "CodeQL"
-
-on:
-  push:
-    branches: [ "master" ]
-  pull_request:
-    # The branches below must be a subset of the branches above
-    branches: [ "master" ]
-  schedule:
-    - cron: '21 20 * * 5'
-
-jobs:
-  analyze:
-    name: Analyze
-    runs-on: ubuntu-latest
-    permissions:
-      actions: read
-      contents: read
-      security-events: write
-
-    strategy:
-      fail-fast: false
-      matrix:
-        language: [ 'cpp', 'python' ]
-        # CodeQL supports [ 'cpp', 'csharp', 'go', 'java', 'javascript', 'python', 'ruby' ]
-        # Learn more about CodeQL language support at https://aka.ms/codeql-docs/language-support
-
-    steps:
-    - name: Checkout repository
-      uses: actions/checkout@v5
-
-    # Initializes the CodeQL tools for scanning.
-    - name: Initialize CodeQL
-      uses: github/codeql-action/init@v3
-      with:
-        languages: ${{ matrix.language }}
-        # If you wish to specify custom queries, you can do so here or in a config file.
-        # By default, queries listed here will override any specified in a config file.
-        # Prefix the list here with "+" to use these queries and those in the config file.
-        
-        # Details on CodeQL's query packs refer to : https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-code-scanning#using-queries-in-ql-packs
-        # queries: security-extended,security-and-quality
-
-        
-    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
-    # If this step fails, then you should remove it and run the build manually (see below)
-    - name: Autobuild
-      uses: github/codeql-action/autobuild@v3
-
-    # ℹ️ Command-line programs to run using the OS shell.
-    # 📚 See https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsrun
-
-    #   If the Autobuild fails above, remove it and uncomment the following three lines. 
-    #   modify them (or add more) to build your code if your project, please refer to the EXAMPLE below for guidance.
-
-    # - run: |
-    #   echo "Run, Build Application using script"
-    #   ./location_of_script_within_repo/buildscript.sh
-
-    - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v3

.github/workflows/mingw-w64-msys2.yml

@@ -7,7 +7,11 @@ on:
       - devel
     paths:
     - 'tiny_gltf.*'
+    - 'tinygltf_json_c.h'
     - 'CMakeLists.txt'
+    - 'meson.build'
+    - 'meson_options.txt'
+    - 'tests/tester_v3*.c'
     - '.github/workflows/mingw-w64-msys2.yml'
   pull_request:
   workflow_dispatch:
@@ -37,9 +41,13 @@ jobs:
           cmake \
             -G"Ninja" \
             -S . \
-            -B build
+            -B build \
+            -DTINYGLTF_BUILD_TESTS=ON
 
       - name: Build
         run: |
           cmake --build build
 
+      - name: Run tests
+        run: |
+          ctest --test-dir build --output-on-failure

CMakeLists.txt

@@ -41,6 +41,21 @@ endif (TINYGLTF_BUILD_BUILDER_EXAMPLE)
 
 if (TINYGLTF_BUILD_TESTS)
   enable_testing()
+
+  function(add_tinygltf_v3_c_test target)
+    add_executable(${target} ${ARGN})
+    target_include_directories(${target} PRIVATE
+      ${CMAKE_CURRENT_SOURCE_DIR}
+      ${CMAKE_CURRENT_SOURCE_DIR}/tests
+    )
+    set_target_properties(${target} PROPERTIES
+      C_STANDARD 11
+      C_STANDARD_REQUIRED ON
+      C_EXTENSIONS OFF
+    )
+    add_test(NAME ${target} COMMAND ${target} WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/tests)
+  endfunction()
+
   add_executable(tester tests/tester.cc)
   target_include_directories(tester PRIVATE
     ${CMAKE_CURRENT_SOURCE_DIR}
@@ -66,20 +81,18 @@ if (TINYGLTF_BUILD_TESTS)
   target_compile_definitions(tester_intensive_customjson PRIVATE TINYGLTF_USE_CUSTOM_JSON)
   add_test(NAME tester_intensive_customjson COMMAND tester_intensive_customjson WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/tests)
 
-  add_executable(tester_v3_c
-    tests/tester_v3_c.c
-    tiny_gltf_v3.c
-  )
-  target_include_directories(tester_v3_c PRIVATE
-    ${CMAKE_CURRENT_SOURCE_DIR}
-    ${CMAKE_CURRENT_SOURCE_DIR}/tests
-  )
-  set_target_properties(tester_v3_c PROPERTIES
-    C_STANDARD 11
-    C_STANDARD_REQUIRED ON
-    C_EXTENSIONS OFF
-  )
-  add_test(NAME tester_v3_c COMMAND tester_v3_c WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/tests)
+  add_tinygltf_v3_c_test(tester_v3_c tests/tester_v3_c.c tiny_gltf_v3.c)
+  target_compile_definitions(tester_v3_c PRIVATE TINYGLTF3_ENABLE_FS)
+
+  add_tinygltf_v3_c_test(tester_v3_c_v1port tests/tester_v3_c_v1port.c tiny_gltf_v3.c)
+  target_compile_definitions(tester_v3_c_v1port PRIVATE TINYGLTF3_ENABLE_FS)
+
+  add_tinygltf_v3_c_test(tester_v3_json_c tests/tester_v3_json_c.c)
+
+  add_tinygltf_v3_c_test(tester_v3_freestanding tests/tester_v3_freestanding.c)
+  if (CMAKE_C_COMPILER_ID MATCHES "Clang|GNU")
+    target_compile_options(tester_v3_freestanding PRIVATE -ffreestanding)
+  endif()
 endif (TINYGLTF_BUILD_TESTS)
 
 #

README.md

@@ -61,8 +61,10 @@ The v3 C runtime is built for processing **untrusted glTF/GLB input** (server-si
 
 - **URI sanitization** — external buffer/image URIs are rejected before any filesystem call if they are empty, contain NUL bytes, begin with `/` or `\`, look like a Windows drive prefix (`X:`), or contain a `..` segment. Production callers SHOULD still provide a custom `tg3_fs_callbacks.read_file` that confines reads to a known directory (e.g. via `openat` plus a `realpath` prefix check) when the input is attacker-controlled.
 - **Index bounds validation** — every `int32_t` index field populated from JSON (accessor.bufferView, primitive.indices/material/attributes, scene.nodes[], skin.joints[], animation channel/sampler refs, KHR_audio + MSFT_lod refs, …) is checked after the structural parse. Out-of-range indices produce `TG3_ERR_INVALID_INDEX`. Default `tg3_parse_options.validate_indices = 1`; set to `0` only when you need raw round-trip and have your own validator.
+- **Buffer/accessor range validation** — declared buffer lengths, bufferView ranges, accessor element spans, sparse accessor spans, component types, and overflow-prone size math are checked before returning a model.
 - **Strict numeric range checks** — JSON numbers feeding integer fields go through finite/round-trip-validated coercion (`tg3__json_number_to_int32` / `_uint64`). `byteStride` is restricted to 0 or [4, 252].
-- **Memory budget** — the arena is capped at `TINYGLTF3_MAX_MEMORY_BYTES` (1 GB by default; configurable via `tg3_memory_config`).
+- **Memory budget** — the arena and C JSON parser enforce `TINYGLTF3_MAX_MEMORY_BYTES` by default; `max_single_alloc` and `TINYGLTF3_MAX_STRING_LENGTH` bound individual allocation and string size.
+- **Opt-in fast paths** — `skip_extras_values` avoids materializing `extras` and unknown extension value trees, and `borrow_input_buffers` lets GLB buffer spans reference caller-owned input bytes instead of copying the BIN chunk.
 - **Image decoding off by default** — the parser does not decode image bytes; use `tg3_parse_options.images_as_is = 1` to skip any decoder entirely when handling untrusted input.
 - **Error message lifetime** — error strings on `tg3_error_stack` are arena-allocated and remain valid until `tg3_model_free()`. Read or copy them BEFORE freeing the model.
 

benchmark/bench_v3.cpp

@@ -139,7 +139,9 @@ struct BenchResult {
 /* ------------------------------------------------------------------ */
 
 static BenchResult bench_file(const char *filename, int iterations, int warmup,
-                               bool quiet, int float32_mode = 0) {
+                               bool quiet, int float32_mode = 0,
+                               int skip_extras_values = 0,
+                               int borrow_input_buffers = 0) {
     BenchResult r = {};
     r.filename = filename;
     r.iterations = iterations;
@@ -199,6 +201,8 @@ static BenchResult bench_file(const char *filename, int iterations, int warmup,
         opts.memory.allocator.free = tracked_free;
         opts.memory.allocator.user_data = &tracker;
         opts.parse_float32 = float32_mode;
+        opts.skip_extras_values = skip_extras_values;
+        opts.borrow_input_buffers = borrow_input_buffers;
 
         tg3_model model;
         tg3_error_stack errors;
@@ -340,7 +344,11 @@ static void usage() {
         "  --csv            Output in CSV format\n"
         "  --quiet          Suppress per-iteration error messages\n"
         "  --batch          Benchmark multiple files\n"
-        "  --float32        Parse JSON floats as float32 (faster, less precise)\n");
+        "  --float32        Parse JSON floats as float32 (faster, less precise)\n"
+        "  --skip-extras-values\n"
+        "                   Skip materializing extras/unknown extension values\n"
+        "  --borrow-input-buffers\n"
+        "                   Let GLB buffers reference caller-owned input bytes\n");
 }
 
 int main(int argc, char **argv) {
@@ -351,6 +359,8 @@ int main(int argc, char **argv) {
     bool csv = false;
     bool quiet = false;
     int float32_mode = 0;
+    int skip_extras_values = 0;
+    int borrow_input_buffers = 0;
     std::vector<std::string> files;
 
     for (int i = 1; i < argc; ++i) {
@@ -364,6 +374,10 @@ int main(int argc, char **argv) {
             quiet = true;
         } else if (strcmp(argv[i], "--float32") == 0) {
             float32_mode = 1;
+        } else if (strcmp(argv[i], "--skip-extras-values") == 0) {
+            skip_extras_values = 1;
+        } else if (strcmp(argv[i], "--borrow-input-buffers") == 0) {
+            borrow_input_buffers = 1;
         } else if (strcmp(argv[i], "--batch") == 0) {
             /* batch mode: just collect files */
         } else if (argv[i][0] != '-') {
@@ -379,10 +393,14 @@ int main(int argc, char **argv) {
         if (!csv && !quiet) {
             printf("Benchmarking: %s (%d iterations, %d warmup%s)\n",
                    file.c_str(), iterations, warmup,
-                   float32_mode ? ", float32" : "");
+                   float32_mode ? ", float32" :
+                   skip_extras_values ? ", skip extras" :
+                   borrow_input_buffers ? ", borrow buffers" : "");
         }
 
-        BenchResult r = bench_file(file.c_str(), iterations, warmup, quiet, float32_mode);
+        BenchResult r = bench_file(file.c_str(), iterations, warmup, quiet,
+                                   float32_mode, skip_extras_values,
+                                   borrow_input_buffers);
 
         if (csv) {
             print_csv_row(r);

meson.build

@@ -0,0 +1,52 @@
+project(
+  'tinygltf',
+  'c',
+  default_options: ['c_std=c11'],
+  meson_version: '>=0.55.0',
+)
+
+tinygltf_inc = include_directories('.', 'tests')
+
+if get_option('tests')
+  tests_workdir = join_paths(meson.current_source_dir(), 'tests')
+  cc = meson.get_compiler('c')
+
+  tester_v3_c = executable(
+    'tester_v3_c',
+    ['tests/tester_v3_c.c', 'tiny_gltf_v3.c'],
+    include_directories: tinygltf_inc,
+    c_args: ['-DTINYGLTF3_ENABLE_FS'],
+    install: false,
+  )
+  test('tester_v3_c', tester_v3_c, workdir: tests_workdir)
+
+  tester_v3_c_v1port = executable(
+    'tester_v3_c_v1port',
+    ['tests/tester_v3_c_v1port.c', 'tiny_gltf_v3.c'],
+    include_directories: tinygltf_inc,
+    c_args: ['-DTINYGLTF3_ENABLE_FS'],
+    install: false,
+  )
+  test('tester_v3_c_v1port', tester_v3_c_v1port, workdir: tests_workdir)
+
+  tester_v3_json_c = executable(
+    'tester_v3_json_c',
+    'tests/tester_v3_json_c.c',
+    include_directories: tinygltf_inc,
+    install: false,
+  )
+  test('tester_v3_json_c', tester_v3_json_c, workdir: tests_workdir)
+
+  freestanding_args = []
+  if cc.get_id() in ['clang', 'gcc']
+    freestanding_args += ['-ffreestanding']
+  endif
+  tester_v3_freestanding = executable(
+    'tester_v3_freestanding',
+    'tests/tester_v3_freestanding.c',
+    include_directories: tinygltf_inc,
+    c_args: freestanding_args,
+    install: false,
+  )
+  test('tester_v3_freestanding', tester_v3_freestanding, workdir: tests_workdir)
+endif

meson_options.txt

@@ -0,0 +1 @@
+option('tests', type: 'boolean', value: true, description: 'Build and run tinygltf tests')

tests/Makefile

@@ -1,7 +1,7 @@
 # Use this for strict compilation check(will work on clang 3.8+)
 #EXTRA_CXXFLAGS := -fsanitize=address -Wall -Werror -Weverything -Wno-c++11-long-long -DTINYGLTF_APPLY_CLANG_WEVERYTHING
 
-all: ../tiny_gltf.h tester_v3_c tester_v3_c_v1port
+all: ../tiny_gltf.h tester_v3_c tester_v3_c_v1port tester_v3_json_c tester_v3_freestanding
 	clang++  -I../ $(EXTRA_CXXFLAGS) -std=c++11 -g -O0 -o tester tester.cc
 	clang++ -DTINYGLTF_NOEXCEPTION -I../ $(EXTRA_CXXFLAGS) -std=c++11 -g -O0 -o tester_noexcept tester.cc
 	clang++ -DTINYGLTF_USE_CUSTOM_JSON -I../ $(EXTRA_CXXFLAGS) -std=c++11 -g -O0 -o tester_intensive_customjson tester_intensive_customjson.cc
@@ -11,3 +11,9 @@ tester_v3_c: tester_v3_c.c ../tiny_gltf_v3.h ../tiny_gltf_v3.c ../tinygltf_json_
 
 tester_v3_c_v1port: tester_v3_c_v1port.c ../tiny_gltf_v3.h ../tiny_gltf_v3.c ../tinygltf_json_c.h
 	clang -I../ -std=c11 -g -O0 -DTINYGLTF3_ENABLE_FS -o tester_v3_c_v1port tester_v3_c_v1port.c ../tiny_gltf_v3.c
+
+tester_v3_json_c: tester_v3_json_c.c ../tinygltf_json_c.h
+	clang -I../ -std=c11 -g -O0 -o tester_v3_json_c tester_v3_json_c.c
+
+tester_v3_freestanding: tester_v3_freestanding.c ../tiny_gltf_v3.h ../tiny_gltf_v3.c ../tinygltf_json_c.h
+	clang -I../ -std=c11 -ffreestanding -g -O0 -o tester_v3_freestanding tester_v3_freestanding.c

tests/tester_v3_freestanding.c

@@ -0,0 +1,75 @@
+#include <stddef.h>
+#include <stdint.h>
+
+static union {
+  uint64_t align;
+  unsigned char bytes[512 * 1024];
+} test_heap;
+static size_t test_heap_used;
+
+static void *test_malloc(size_t size) {
+  size_t total = (size + sizeof(size_t) + 7u) & ~(size_t)7u;
+  if (test_heap_used + total > sizeof(test_heap.bytes)) return 0;
+  {
+    unsigned char *base = test_heap.bytes + test_heap_used;
+    *((size_t *)base) = size;
+    test_heap_used += total;
+    return base + sizeof(size_t);
+  }
+}
+
+static void *test_realloc(void *ptr, size_t size) {
+  unsigned char *old_base;
+  size_t old_size;
+  unsigned char *new_ptr;
+  size_t n;
+  size_t i;
+  if (!ptr) return test_malloc(size);
+  old_base = (unsigned char *)ptr - sizeof(size_t);
+  old_size = *((size_t *)old_base);
+  new_ptr = (unsigned char *)test_malloc(size);
+  if (!new_ptr) return 0;
+  n = old_size < size ? old_size : size;
+  for (i = 0; i < n; ++i) new_ptr[i] = ((unsigned char *)ptr)[i];
+  return new_ptr;
+}
+
+static void test_free(void *ptr) {
+  (void)ptr;
+}
+
+#define TINYGLTF3_NO_STDLIB
+#define TINYGLTF3_MALLOC(sz) test_malloc(sz)
+#define TINYGLTF3_REALLOC(ptr, sz) test_realloc((ptr), (sz))
+#define TINYGLTF3_FREE(ptr) test_free(ptr)
+#define TINYGLTF3_IMPLEMENTATION
+#include "tiny_gltf_v3.h"
+
+static int streq(tg3_str s, const char *lit, uint32_t len) {
+  uint32_t i;
+  if (!s.data || s.len != len) return 0;
+  for (i = 0; i < len; ++i) {
+    if (s.data[i] != lit[i]) return 0;
+  }
+  return 1;
+}
+
+int main(void) {
+  static const uint8_t json[] =
+      "{\"asset\":{\"version\":\"2.0\"},\"nodes\":[{\"name\":\"free\"}]}";
+  tg3_model model;
+  tg3_error_stack errors;
+  tg3_parse_options opts;
+  tg3_error_code err;
+
+  tg3_error_stack_init(&errors);
+  tg3_parse_options_init(&opts);
+  err = tg3_parse_auto(&model, &errors, json, (uint64_t)(sizeof(json) - 1),
+                       "", 0, &opts);
+  if (err != TG3_OK) return 1;
+  if (model.nodes_count != 1) return 3;
+  if (!streq(model.nodes[0].name, "free", 4)) return 4;
+  tg3_model_free(&model);
+  tg3_error_stack_free(&errors);
+  return 0;
+}

tests/tester_v3_json_c.c

@@ -0,0 +1,165 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#define TINYGLTF_JSON_C_IMPLEMENTATION
+#include "tinygltf_json_c.h"
+
+static uint64_t dbl_bits(double v) {
+  uint64_t bits;
+  memcpy(&bits, &v, sizeof(bits));
+  return bits;
+}
+
+static double dbl_from_bits(uint64_t bits) {
+  double v;
+  memcpy(&v, &bits, sizeof(v));
+  return v;
+}
+
+static int check_stringify(const char *json, const char *expected) {
+  tg3json_value v;
+  const char *err = NULL;
+  char *out;
+  size_t out_len = 0;
+  int ok = 1;
+  if (!tg3json_parse(json, json + strlen(json), 128, &v, &err)) {
+    fprintf(stderr, "parse failed for %s at %td\n", json, err ? err - json : -1);
+    return 0;
+  }
+  out = tg3json_stringify(&v, &out_len);
+  if (!out || strcmp(out, expected) != 0) {
+    fprintf(stderr, "stringify(%s) = %s, expected %s\n",
+            json, out ? out : "(null)", expected);
+    ok = 0;
+  }
+  if (out) TINYGLTF_JSON_FREE(out);
+  tg3json_value_free(&v);
+  return ok;
+}
+
+static int check_parse_rejects(const char *json) {
+  tg3json_value v;
+  const char *err = NULL;
+  if (tg3json_parse(json, json + strlen(json), 128, &v, &err)) {
+    fprintf(stderr, "parse unexpectedly accepted %s\n", json);
+    tg3json_value_free(&v);
+    return 0;
+  }
+  return 1;
+}
+
+static int check_roundtrip(const char *json) {
+  tg3json_value a;
+  tg3json_value b;
+  const char *err = NULL;
+  char *out;
+  size_t out_len = 0;
+  int ok = 1;
+  if (!tg3json_parse(json, json + strlen(json), 128, &a, &err)) return 0;
+  out = tg3json_stringify(&a, &out_len);
+  if (!out || !tg3json_parse(out, out + out_len, 128, &b, &err)) {
+    ok = 0;
+  } else if (a.type != TG3JSON_REAL ||
+             !((b.type == TG3JSON_REAL && dbl_bits(a.u.real) == dbl_bits(b.u.real)) ||
+               (b.type == TG3JSON_INT && dbl_bits(a.u.real) == dbl_bits((double)b.u.integer)))) {
+    fprintf(stderr, "roundtrip changed bits: %s -> %s\n", json, out);
+    ok = 0;
+  }
+  if (out) TINYGLTF_JSON_FREE(out);
+  tg3json_value_free(&a);
+  tg3json_value_free(&b);
+  return ok;
+}
+
+static int check_parse_bits(const char *json, uint64_t expected_bits) {
+  tg3json_value v;
+  const char *err = NULL;
+  if (!tg3json_parse(json, json + strlen(json), 128, &v, &err)) {
+    fprintf(stderr, "parse failed for %s at %td\n", json, err ? err - json : -1);
+    return 0;
+  }
+  if (v.type != TG3JSON_REAL || dbl_bits(v.u.real) != expected_bits) {
+    fprintf(stderr, "parse bits mismatch: %s -> 0x%llx, expected 0x%llx\n",
+            json, (unsigned long long)(v.type == TG3JSON_REAL ? dbl_bits(v.u.real) : 0),
+            (unsigned long long)expected_bits);
+    tg3json_value_free(&v);
+    return 0;
+  }
+  tg3json_value_free(&v);
+  return 1;
+}
+
+static int check_parse_float32(void) {
+  static const char json[] = "0.10000000149011612";
+  tg3json_parse_options opts;
+  tg3json_value v;
+  const char *err = NULL;
+  double expected = (double)(float)0.10000000149011612;
+  memset(&opts, 0, sizeof(opts));
+  opts.parse_float32 = 1;
+  if (!tg3json_parse_n_opts(json, strlen(json), &opts, &v, &err)) {
+    fprintf(stderr, "parse_float32 parse failed\n");
+    return 0;
+  }
+  if (v.type != TG3JSON_REAL || dbl_bits(v.u.real) != dbl_bits(expected)) {
+    fprintf(stderr, "parse_float32 did not round through float\n");
+    tg3json_value_free(&v);
+    return 0;
+  }
+  tg3json_value_free(&v);
+  return 1;
+}
+
+static int check_nonfinite_stringifies_to_null(void) {
+  tg3json_value v;
+  char *out;
+  size_t len = 0;
+  int ok;
+  tg3json_value_init_real(&v, dbl_from_bits(0x7ff0000000000000ULL));
+  out = tg3json_stringify(&v, &len);
+  ok = out && strcmp(out, "null") == 0;
+  if (!ok) fprintf(stderr, "inf stringify = %s\n", out ? out : "(null)");
+  if (out) TINYGLTF_JSON_FREE(out);
+  tg3json_value_free(&v);
+  if (!ok) return 0;
+
+  tg3json_value_init_real(&v, dbl_from_bits(0x7ff8000000000001ULL));
+  out = tg3json_stringify(&v, &len);
+  ok = out && strcmp(out, "null") == 0;
+  if (!ok) fprintf(stderr, "nan stringify = %s\n", out ? out : "(null)");
+  if (out) TINYGLTF_JSON_FREE(out);
+  tg3json_value_free(&v);
+  return ok;
+}
+
+int main(void) {
+  int ok = 1;
+  ok = check_stringify("1.0", "1") && ok;
+  ok = check_stringify("-1.0", "-1") && ok;
+  ok = check_stringify("0.1", "0.1") && ok;
+  ok = check_stringify("0.0001", "0.0001") && ok;
+  ok = check_stringify("0.00001", "1e-5") && ok;
+  ok = check_stringify("1000000000000000.0", "1000000000000000") && ok;
+  ok = check_stringify("10000000000000000.0", "1e16") && ok;
+  ok = check_roundtrip("1.2345678901234567") && ok;
+  ok = check_roundtrip("2.2250738585072014e-308") && ok;
+  ok = check_roundtrip("5e-324") && ok;
+  ok = check_roundtrip("-5e-324") && ok;
+  ok = check_roundtrip("9007199254740993.0") && ok;
+  ok = check_parse_bits("1.23456789012345678901", 0x3ff3c0ca428c59fbULL) && ok;
+  ok = check_parse_bits("1.234567890123456789012345678901234567890e-100",
+                        0x2b31482fe620c5d2ULL) && ok;
+  ok = check_parse_bits("1.7976931348623157e308", 0x7fefffffffffffffULL) && ok;
+  ok = check_parse_float32() && ok;
+  ok = check_nonfinite_stringifies_to_null() && ok;
+  ok = check_parse_rejects("+1") && ok;
+  ok = check_parse_rejects("01") && ok;
+  ok = check_parse_rejects("1.") && ok;
+  ok = check_parse_rejects("1e") && ok;
+  ok = check_parse_rejects("1e400") && ok;
+  ok = check_parse_rejects("-1e400") && ok;
+  ok = check_parse_rejects("1.7976931348623159e308") && ok;
+  ok = check_parse_rejects("[1,]") && ok;
+  return ok ? 0 : 1;
+}

tiny_gltf.h

@@ -7059,7 +7059,11 @@ static void SerializeNumberProperty(const std::string &key, T number,
   detail::JsonAddMember(obj, key.c_str(), detail::json(number));
 }
 
-#ifdef TINYGLTF_USE_RAPIDJSON
+#if defined(TINYGLTF_USE_RAPIDJSON) || defined(TINYGLTF_USE_CUSTOM_JSON)
+// size_t needs an explicit cast to uint64_t: on platforms where size_t is
+// neither int64_t nor uint64_t (e.g. macOS ARM64 where it is unsigned long,
+// or 32-bit targets where it is unsigned int) constructing detail::json
+// directly from a size_t is an ambiguous overload.
 template <>
 void SerializeNumberProperty(const std::string &key, size_t number,
                              detail::json &obj) {

tiny_gltf_v3.h

@@ -116,8 +116,12 @@
 
 /* Assert override */
 #ifndef TINYGLTF3_ASSERT
+#ifndef TINYGLTF3_NO_STDLIB
 #include <assert.h>
 #define TINYGLTF3_ASSERT(x) assert(x)
+#else
+#define TINYGLTF3_ASSERT(x) ((void)(x))
+#endif
 #endif
 
 /* ======================================================================
@@ -127,8 +131,34 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdarg.h>
+#ifndef TINYGLTF3_NO_STDLIB
 #include <string.h>
 #include <stdlib.h>
+#endif
+
+#ifndef TINYGLTF3_MALLOC
+#ifndef TINYGLTF3_NO_STDLIB
+#define TINYGLTF3_MALLOC(sz) malloc(sz)
+#else
+#define TINYGLTF3_MALLOC(sz) NULL
+#endif
+#endif
+
+#ifndef TINYGLTF3_REALLOC
+#ifndef TINYGLTF3_NO_STDLIB
+#define TINYGLTF3_REALLOC(ptr, sz) realloc((ptr), (sz))
+#else
+#define TINYGLTF3_REALLOC(ptr, sz) NULL
+#endif
+#endif
+
+#ifndef TINYGLTF3_FREE
+#ifndef TINYGLTF3_NO_STDLIB
+#define TINYGLTF3_FREE(ptr) free(ptr)
+#else
+#define TINYGLTF3_FREE(ptr) ((void)(ptr))
+#endif
+#endif
 
 /* ======================================================================
  * Section 4: Constants and Enums
@@ -418,6 +448,7 @@ typedef struct tg3_asset {
 /* --- Buffer --- */
 typedef struct tg3_buffer {
     tg3_str       name;
+    uint64_t      byte_length;  /* Declared buffer.byteLength */
     tg3_span_u8   data;
     tg3_str       uri;
     tg3_extras_ext ext;
@@ -941,6 +972,10 @@ typedef struct tg3_parse_options {
     int32_t  images_as_is;              /* 1 = don't decode images */
     int32_t  preserve_image_channels;   /* 1 = keep original channels */
     int32_t  store_original_json;       /* 1 = store raw JSON strings */
+    int32_t  skip_extras_values;        /* 1 = skip materializing extras and
+                                        *     unknown extension value trees */
+    int32_t  borrow_input_buffers;      /* 1 = GLB BIN buffer spans may point
+                                        *     into caller-owned input data */
     int32_t  parse_float32;            /* 1 = parse JSON floats as float32 for speed
                                         *     (breaks strict double-precision conformance
                                         *      but sufficient for glTF data which is