dotnet/runtime

Сhecking for NULL

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#92,566 opened on Sep 24, 2023

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 (2 comments) (1 reaction) (0 assignees)C# (5,445 forks)batch import
area-TypeSystem-coreclrhelp wanted

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Description

Description

We have two pointer pMT dereferences: https://github.com/dotnet/runtime/blob/cc2670b53ecc1576d3aa1a1011476c99372adfd7/src/coreclr/vm/typedesc.cpp#L888 https://github.com/dotnet/runtime/blob/cc2670b53ecc1576d3aa1a1011476c99372adfd7/src/coreclr/vm/typedesc.cpp#L909 And they are absolutely identical. But before the second dereference there is a check for NULL, before the first there is not. I assume two options. The first option is an unnecessary check. The second option is that the pointer at the first dereference can really be NULL. Between these two dereferences, the pointer pMT itself does not change. Only the following lines: https://github.com/dotnet/runtime/blob/cc2670b53ecc1576d3aa1a1011476c99372adfd7/src/coreclr/vm/typedesc.cpp#L890-L898 Found by Linux Verification Center (portal.linuxtesting.ru) with SVACE.

Author A. Voronin.

Contributor guide

Research direction
Analyze the two dereferences of pMT in typedesc.cpp. Check if the pointer can be NULL at the first dereference by examining the code between the dereferences (lines 890-898). Determine whether the NULL check before the second dereference is redundant or if the first dereference lacks necessary protection.
Tech stack
cppcsharp
Domain
backendinfrastructure
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++debugging
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50