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By Marco Arena | Feb 22, 2024 01:18 AM | Tags: sobjectizer intermediate c++20
A new episode of the series about SObjectizer and message passing:
SObjectizer Tales – 20. Performance, part 1
by Marco Arena
From the article:
In this episode we embark on a three-part full-immersion on performance metrics and considerations in message-passing styled applications, with a specific emphasis on SObjectizer and the in-process actor model.
By Blog Staff | Feb 20, 2024 10:49 AM | Tags: None
In this post, Victor talks about bringing compile times of the {fmt} library on par with the C standard I/O library (stdio).
Optimizing the Unoptimizable: A Journey to Faster C++ Compile Times
by Victor Zverovich
From the article:
First some background: {fmt} is a popular open-source formatting library for C++ that provides a better alternative to C++ iostreams and C stdio. It has already surpassed stdio in many areas:
- Type safety with compile-time format string checks available by default since C++20 and as an opt in for C++14/17. Runtime format strings are also safe to use in {fmt} which is impossible to achieve in
printf.- Extensibility: user-defined type can be made formattable and most standard library types such as containers, dates and times are formattable out of the box.
- Performance: {fmt} is significantly faster than common standard library implementations of
printf, in some cases by an order of magnitude (e.g. on floating-point formatting).- Portable Unicode support.
However, one area where stdio remained significantly better was compile times.
By Blog Staff | Feb 16, 2024 10:46 AM | Tags: None
In this software troubleshooting case, a customer experienced program crashes, and a detailed analysis of the code revealed several issues. The primary problem stemmed from lazy initialization of a widget list, leading to inconsistent vector states and potential crashes. Additionally, a multithreading issue was identified, highlighting the importance of thread-safety mechanisms in code that can be accessed concurrently.
The Case of the Vector With an Impossibly Large Size
by Raymond Chen
From the article:
A customer had a program that crashed with this stack:
contoso!Widget::GetCost contoso!StandardWidgets::get_TotalCost+0x12f rpcrt4!Invoke+0x73 rpcrt4!Ndr64StubWorker+0xb9b rpcrt4!NdrStubCall3+0xd7 combase!CStdStubBuffer_Invoke+0xdb combase!ObjectMethodExceptionHandlingAction<<lambda_...> >+0x47 combase!DefaultStubInvoke+0x376 combase!ServerCall::ContextInvoke+0x6f3 combase!ComInvokeWithLockAndIPID+0xacb combase!ThreadInvoke+0x103 rpcrt4!DispatchToStubInCNoAvrf+0x18 rpcrt4!RPC_INTERFACE::DispatchToStubWorker+0x1a9 rpcrt4!RPC_INTERFACE::DispatchToStubWithObject+0x1a7 rpcrt4!LRPC_SCALL::DispatchRequest+0x308 rpcrt4!LRPC_SCALL::HandleRequest+0xdcb rpcrt4!LRPC_SASSOCIATION::HandleRequest+0x2c3 rpcrt4!LRPC_ADDRESS::HandleRequest+0x183 rpcrt4!LRPC_ADDRESS::ProcessIO+0x939 rpcrt4!LrpcIoComplete+0xff ntdll!TppAlpcpExecuteCallback+0x14d ntdll!TppWorkerThread+0x4b4 kernel32!BaseThreadInitThunk+0x18 ntdll!RtlUserThreadStart+0x21They wondered if some recent change to Windows was the source of the problem, since it didn’t happen as much in earlier versions of Windows.
By Marco Arena | Feb 14, 2024 11:31 PM | Tags: sobjectizer intermediate c++20
A new episode of the series about SObjectizer and message passing:
SObjectizer Tales – 19. Thread-safe handlers
by Marco Arena
From the article:
In this episode we explore thread-safe message handlers and revisit the problem of distributing work across multiple threads.
By Blog Staff | Feb 13, 2024 05:34 PM | Tags: None
We delve into how C++20 introduced changes to object comparisons, leading to unexpected behavior and the need for matching operator!= declarations.
DR20 - The Equality Operator You Are Looking For
by Sandor Dargo
From the article:
When I see DR, I immediately think about Disaster Recovery. That’s due to my first corporate job where I worked as a Database Administrator and we had regular exercises to simulate events when datacenters would be unavailable.
When you see DR in the title of a C++ proposal, it’s not about a disaster, it’s more about a bug. DR stands for defect report. But the paper itself is usually not about reporting that there is a problem - that has been already done -, but more about proposing a solution.
What’s more important is that defect reports are not becoming part of the latest standard, they retrospectively change the one that introduced the defect.
A defect of C++20’s equality operator
P2468R2 is addressing a problem that was introduced by C++20. C++20 brought us the spaceship operator (
operator<=>), but it further changed the logic of object comparisons. It changed the meaning of==and!=and how overload resolution applies to them.
By Blog Staff | Feb 9, 2024 01:05 PM | Tags: None
Sometimes the small changes between two C++ standards really bite you. Today's post is about when I got bitten by a change to aggregates in C++20.
Aggregates: C++17 vs. C++20
by Andreas Fertig
From the article:
Attendees of my training classes usually assume that I know everything. I can say sorry, but that's not the case. One day in the past, I showed the following example during a class:
struct Point { int x; int y; }; Point pt{2, 3};The class did cover C++17 and C++20. The code of
Pointis a reduced version for this post. We were talking about C++17's structured bindings. I usePointto show the decomposition using C++ Insights.I showed the behavior and certain variations while answering questions from the attendees. One question was about move and copy. The question leads me changing the initial code to the following one:
struct Point { int x; int y; Point(Point&&) = delete; A }; Point pt{2, 3};
2 3 4 5 6 7 8 |
|
As you can see, in A, I deleted the move constructor. As far as I remember, this topic was more or less the last one for this day. Everything went well and as expected.
The next morning one of the attendees approached me with the question of why the code didn't compile on his machine. My usual answer here is that if C++ were be easy, I wouldn't have the job I have. Somehow this never shuts down such questions. I like curious attendees.
He shared his code via Compiler Explorer. Guess what? His code looked exactly like mine but didn't compile. Here is the error message from the compiler:
By Marco Arena | Feb 8, 2024 12:36 AM | Tags: sobjectizer intermediate c++20
A new episode of the series about SObjectizer and message passing:
SObjectizer Tales – 18. Limiting message chains
by Marco Arena
From the article:
In this episode we explore limited message chains as an alternative way to regulating message flow.
By Eric Niebler | Feb 6, 2024 12:46 PM | Tags: c++26
In a recent blog post, Eric Niebler gets inside the soon-to-be-standard async programming model and shows why you should care.
What are senders good for, anyway?
by Eric Niebler
From the article:
At the heart of P2300 is a simple, elegant (IMHO) core that brings many benefits, but it’s hard to see that forest for all the trees.
So let’s make this concrete. In this post, I’ll show how to bring a crusty old C-style async API into the world of senders, and why you might want to do that.
By Felix Petriconi | Feb 4, 2024 07:07 AM | Tags: None
In his recent blog post brilliantsugar talks about technics to find race conditions in multithreading code by using different tools.
How I Learned to Stop Worrying and Love Juggling C++ Atomics
by brilliantsugar
From the blog post
As most C++ programmers are aware, courtesy of Herb Sutter, programming lock-free data structures is akin to juggling razor blades. Reasoning about concurrent programs is already complex enough but modern CPU memory models are so complicated that they manage to make it even harder. The prevailing suggestion you often come across is to steer clear of lock-free programming entirely.
In this article, I share the adventures of exploring methods for formally verifying lock-free C++ code. To showcase three different approaches, I delve into the implementation of a lock-free triple buffer data structure.
By Andrzej Krzemienski | Feb 4, 2024 06:05 AM | Tags: None
Andrzej talks in his recent blog post about class invariants.
Class Invariants
by Andrzej Krzemieński
About the blog post:
The primary motivation for defining a class in C++ is to reflect and maintain a class invariant. In this post we will see what class invariants are and how you deal with them. Class invariants are important part of C++, even though there is no “invariant” keyword in C++.