Arno Schoedl

The C++ rvalue lifetime disaster

Why do common C++ features like `std::min` and the ternary operator create dangling references? This talk reveals a fundamental language flaw and how to fix it.

The C++ rvalue lifetime disaster
#1about 3 minutes

The dual role of rvalue references in C++

Rvalue references were introduced for move semantics to avoid copies but are also used to manage the lifetime of temporary objects.

#2about 6 minutes

Why temporary lifetime extension fails in modern C++

The pre-C++11 feature for extending temporary object lifetimes does not work correctly with rvalue references, necessitating a custom macro to create a value or reference based on expression type.

#3about 6 minutes

How accessor methods cause rvalue amnesia

Standard accessor methods returning a const lvalue reference incorrectly bind to rvalues, losing critical lifetime information and leading to dangling references.

#4about 4 minutes

A proposal for fixing C++ reference binding rules

A proposed language fix using pragmas would introduce new, safer reference binding rules to prevent short-lived rvalues from binding to long-lived lvalue references.

#5about 3 minutes

Practical mitigations for rvalue lifetime issues today

Use custom macros to manage variable lifetimes, guard member accessors, and implement a correct ternary operator to work around the language's flawed binding rules.

#6about 1 minute

Managing C++ complexity with strong coding guidelines

The best way to manage the growing complexity of C++ is to establish strong internal coding guidelines and use custom libraries to standardize code patterns.

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Designer

Andrew Comp

Andrew Comp
Berlin, Germany

Intermediate
Java
JavaScript

Matching moments

Understanding temporary objects and lifetime extension rules
05:02 MIN

Understanding temporary objects and lifetime extension rules

An (In-)Complete Guide to C++ Object Lifetimes

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Modern C++ evolution and the burden of backward compatibility
07:52 MIN

Modern C++ evolution and the burden of backward compatibility

Eternal Sunshine of the Spotless Programming Language

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Using modern language features for safer code
07:50 MIN

Using modern language features for safer code

C++ in constrained environments

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Implicit destruction and best practices for object lifetime
01:58 MIN

Implicit destruction and best practices for object lifetime

An (In-)Complete Guide to C++ Object Lifetimes

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C++ availability, ecosystem, and backwards compatibility
06:50 MIN

C++ availability, ecosystem, and backwards compatibility

101 brilliant things of C++

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Defining objects and lifetimes in C++
03:06 MIN

Defining objects and lifetimes in C++

An (In-)Complete Guide to C++ Object Lifetimes

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Q&A on language design, Rust, and the future of C++
08:47 MIN

Q&A on language design, Rust, and the future of C++

The Design and Evolution of C++

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Reviewing common memory safety problems in other languages
05:58 MIN

Reviewing common memory safety problems in other languages

A Love Letter to Rust

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