Clang-tidy should detect undefined behaviour on container access

[Tasty213]

Hi,

Spent the day tracking down a segfault that turned out to be because we where calling front on a std::deque and then de-referencing it to call a value on that returned element, but because we hadn't checked the size of the deque first we hit a segfault if it was empty as that's undefined behaviour. Just wondering if there's a clang-tidy check for calling these methods on collections (std::list's front method is also undefined on an empty list)?

Thanks in advance!

[llvmbot]

@llvm/issue-subscribers-clang-static-analyzer

Author: George Sykes (Tasty213)

Hi,

Spent the day tracking down a segfault that turned out to be because we where calling front on a std::deque and then de-referencing it to call a value on that returned element, but because we hadn't checked the size of the deque first we hit a segfault if it was empty as that's undefined behaviour. Just wondering if there's a clang-tidy check for calling these methods on collections (std::list's front method is also undefined on an empty list)?

Thanks in advance!

[EugeneZelenko]

This seems to be task for Clang Static Analyzer because containers may be passed between different functions/translation units.

[Tasty213]

Hi, out of interest does the static analyser only run when you're compiling with Clang? Our current build system uses Scons producing a compilation database that's then fed into clang tidy. Appreciate this isn't the main use case but just why my mind jumped to using clang-tidy.

[EugeneZelenko]

Clang Static Analyzer could be run from Clang-tidy. See clang-analyzer-* checks in https://clang.llvm.org/extra/clang-tidy/checks/list.html.

[nicovank]

The most robust way is to test for those cases at runtime, for example by enabling extra hardening during CI. With libc++, this can be a flag at compile time. This will enable assertions (std::deque::front will throw if empty).