Valgrind warnings in GL::Implementation::State

[xqms]

Hey, I just saw that a very simple application involving a single Texture2D gives warnings under valgrind during exit:

==973387== Conditional jump or move depends on uninitialised value(s)
==973387==    at 0x11FFA6: ~AbstractTexture (AbstractTexture.cpp:238)
==973387==    by 0x11FFA6: Magnum::GL::AbstractTexture::~AbstractTexture() (AbstractTexture.cpp:229)
==973387==    by 0x113F46: ~Texture (Texture.h:102)
==973387==    by 0x113F46: ~App (display_time.cpp:13)
==973387==    by 0x113F46: main (display_time.cpp:40)
==973387==  Uninitialised value was created by a heap allocation
==973387==    at 0x483C583: operator new[](unsigned long) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==973387==    by 0x170D7F: operator() (ArrayTuple.cpp:158)
==973387==    by 0x170D7F: Corrade::Containers::ArrayTuple::ArrayTuple<Corrade::Containers::ArrayTuple::ArrayTuple(Corrade::Containers::ArrayView<Corrade::Containers::ArrayTuple::Item const> const&)::{lambda(unsigned long, unsigned long)#1}>(Corrade::Containers::ArrayView<Corrade::Containers::ArrayTuple::Item const> const&, Corrade::Containers::ArrayTuple::ArrayTuple(Corrade::Containers::ArrayView<Corrade::Containers::ArrayTuple::Item const> const&)::{lambda(unsigned long, unsigned long)#1}) [clone .isra.0] (ArrayTuple.h:424)
==973387==    by 0x170DC8: ArrayTuple (ArrayTuple.cpp:159)
==973387==    by 0x170DC8: Corrade::Containers::ArrayTuple::ArrayTuple(std::initializer_list<Corrade::Containers::ArrayTuple::Item>) (ArrayTuple.cpp:163)
==973387==    by 0x13BB60: Magnum::GL::Implementation::State::allocate(Magnum::GL::Context&, std::ostream*) (State.cpp:115)
==973387==    by 0x135184: Magnum::GL::Context::tryCreate(Magnum::GL::Context::Configuration const&) (Context.cpp:974)
==973387==    by 0x11649A: tryCreate (GLContext.h:157)
==973387==    by 0x11649A: Magnum::Platform::GlfwApplication::tryCreate(Magnum::Platform::GlfwApplication::Configuration const&, Magnum::Platform::GlfwApplication::GLConfiguration const&) (GlfwApplication.cpp:574)
==973387==    by 0x116BC5: Magnum::Platform::GlfwApplication::tryCreate(Magnum::Platform::GlfwApplication::Configuration const&) (GlfwApplication.cpp:318)
==973387==    by 0x116C9C: Magnum::Platform::GlfwApplication::create(Magnum::Platform::GlfwApplication::Configuration const&) (GlfwApplication.cpp:127)
==973387==    by 0x117350: Magnum::Platform::GlfwApplication::GlfwApplication(Magnum::Platform::GlfwApplication::Arguments const&, Magnum::Platform::GlfwApplication::Configuration const&) (GlfwApplication.cpp:69)
==973387==    by 0x1173EF: Magnum::Platform::GlfwApplication::GlfwApplication(Magnum::Platform::GlfwApplication::Arguments const&) (GlfwApplication.cpp:66)
==973387==    by 0x1140F6: App::App(Magnum::Platform::GlfwApplication::Arguments const&) (display_time.cpp:24)
==973387==    by 0x113F25: main (display_time.cpp:40)

Source: https://gist.github.com/xqms/184ffe67e4ac28674183c6ce563c09d9

I tried digging into the GL::Implementation::State myself, but there's scary ArrayTuple stuff there :D But I guess something is going wrong with the ValueInit tag on the textureBinding array?

Maybe I'll have time to investigate further this evening ;)

[mosra]

Oooh.

scary ArrayTuple stuff

Yes :D

ASan didn't tell me a thing. I'll investigate.

[mosra]

No idea why it would complain. I have tests that verify constructors get called on ValueInit'd suballocations, so that should work.

Maybe it's Valgrind misdetecting this because most of the allocation before is not initialized? Does the warning disappear if you put the textureBinding array first in the list passed to the ArrayTuple constructor (so the manual initialization gets done at the start of the allocation already)?

[xqms]

Maybe it's Valgrind misdetecting this because most of the allocation before is not initialized?

Valgrind/memcheck supposedly tracks unintialized values at bit level, so that should not be the case. I'll dig deeper in any case...

[xqms]

Found it! It's a problem in Corrade, so I'll open an issue there.