BUG: memory leak in maplibre-gl-native

[brendan-ward]

Detected in Linux docker container, using valgrind:

==591== 64 bytes in 1 blocks are definitely lost in loss record 1,973 of 2,123
==591==    at 0x483BE63: operator new(unsigned long) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==591==    by 0xE1BF0CD: ???
==591==    by 0xD950063: ???
==591==    by 0x4011B89: call_init.part.0 (dl-init.c:72)
==591==    by 0x4011C90: call_init (dl-init.c:30)
==591==    by 0x4011C90: _dl_init (dl-init.c:119)
==591==    by 0x53E5894: _dl_catch_exception (dl-error-skeleton.c:182)
==591==    by 0x401642C: dl_open_worker (dl-open.c:758)
==591==    by 0x53E5837: _dl_catch_exception (dl-error-skeleton.c:208)
==591==    by 0x40155F9: _dl_open (dl-open.c:837)
==591==    by 0x599234B: dlopen_doit (dlopen.c:66)
==591==    by 0x53E5837: _dl_catch_exception (dl-error-skeleton.c:208)
==591==    by 0x53E5902: _dl_catch_error (dl-error-skeleton.c:227)
==591== 
==591== 5,355 bytes in 255 blocks are definitely lost in loss record 2,121 of 2,123
==591==    at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==591==    by 0x53243BE: strdup (strdup.c:42)
==591==    by 0xD4906F6: ???
==591==    by 0xD4904A4: ???
==591==    by 0xD42F0B9: ???
==591==    by 0x7498436: ??? (in /usr/lib/x86_64-linux-gnu/libGLdispatch.so.0.0.0)
==591==    by 0x7498E1C: __glDispatchMakeCurrent (in /usr/lib/x86_64-linux-gnu/libGLdispatch.so.0.0.0)
==591==    by 0x4EF9ECD: ??? (in /usr/lib/x86_64-linux-gnu/libEGL.so.1.1.0)
==591==    by 0x260B21: mbgl::gl::EGLBackendImpl::activateContext() (in /tmp/build/tests/pymgl_test)
==591==    by 0x2E0BF7: mbgl::gfx::BackendScope::BackendScope(mbgl::gfx::RendererBackend&, mbgl::gfx::BackendScope::ScopeType) (in /tmp/build/tests/pymgl_test)
==591==    by 0x3A3DD8: mbgl::Renderer::~Renderer() (in /tmp/build/tests/pymgl_test)
==591==    by 0x23198D: mbgl::HeadlessFrontend::reset() (in /tmp/build/tests/pymgl_test)
==591== 
==591== LEAK SUMMARY:
==591==    definitely lost: 5,419 bytes in 256 blocks

Looks like a backend is being created within the destructor for the Renderer class.

[brendan-ward]

Note that this occurs for both EGL and GLX backends.

[brendan-ward]

The memory leak only occurs if map is rendered; simply constructing map instances does not trigger it.

The 5,355 bytes lost appears to be stable for the empty style, regardless of how many times rendering is called or how many instances of the map are rendered (e.g., rendering each of 10 maps produces same result as rendering a single map).

Preliminary conclusion: while this is not great, it doesn't appear proportional to load and won't lead to a runaway memory scenario.