llvm/llvm-project

[MIRSampleProfile] nullptr deref crash when profile sample use file not found

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#189764 opened on Mar 31, 2026

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PGOcrash-on-invalidgood first issuellvm:codegen

Description

Trying to reproduce https://github.com/llvm/llvm-project/issues/188897, I failed to pass a valid file for -fprofile-sample-use=; this caused a crash because Reader is nullptr in MIRProfileLoader::runOnFunction. Should be easy to guard against this I think. cc @htyu (author of 958a3d8e2dec95a878dfc9d823861b3a6c674534)

Contributor guide

Tech stack
cpp
Domain
tooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C++ programmingunderstanding of null pointer checks
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Inspect MIRProfileLoader.cpp, specifically the runOnFunction method. Check where Reader is used and add a null pointer check before dereferencing. Refer to commit 958a3d8e2dec95a878dfc9d823861b3a6c674534 for context on the function.