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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 19/09/2026

@pervognsen @wingo I was talking about the shrinking situation on the Rust zulip, and another story we can use is that an uncommitted reservation doesn't create an allocation, only committing. You can therefore split a reservation, decommit it entirely, and then merge it back without shrinking […]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 19/09/2026

@pervognsen @wingo I don't actually now about C++ specifically in this instance, only Rust :D And growing is fine.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 19/09/2026

@pervognsen @wingo But that requires you to know all the pointers to the allocation, so you can launder their provenance.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 19/09/2026

@wingo Depending on how you do it, you also can't do it in LLVM IR. They assume that allocations don't shrink, so once you've treated the first N pages as a single allocation, you can't unmap things at the end.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 18/09/2026

@pervognsen And the C++23 change is actually nice, as it gives you the C++17 behavior back, but can make code ambiguous: eel.is/c++draft/diff.cpp20.dcl

eel.is

[diff.cpp20.dcl]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 18/09/2026

@pervognsen Happens when you introduce UTF-8 string literals before introducing a UTF-8 character type. In theory, char8_t is nice as it's guaranteed to be unsigned and not allowed to alias things, but in practice almost nothing in the standard library supports it.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 06/08/2026

If and hos would you simplify this #cpp code? The code duplication is bugging me. ``` if constexpr (foo<T>) { obj.disableX(); } else if (bar(t)) { obj.disableX(); } else { obj.setX(t.x); } ``` You need an `if constexpr` for the first one, because if `foo<T>` is true, `.x` doesn't exist […]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 20/07/2026

@PeterSommerlad You can use ^^typename std::string if you want the reflection of the type in all cases.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 29/06/2026

@PeterSommerlad They were dropped to get quicker consensus in the NB comment process and will presumably come back in 29: www.open-std.org/jtc1/sc22/wg21/doc…

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 18/06/2026

Current status: rsync'ing .git folders to a remote machine. Because that's how version control works, right?

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 26/05/2026

C++, the programming language where a hypothetical proposal titled "Make <meta> constexpr" would actually add support for runtime reflection.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 12/05/2026

"The problem is that the docs system is writing in Sphinx, and I don't know any Sphinx" - "Yeah, the people who set it up left." - "You mean, they were left in the pyramids after completion."

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 11/05/2026

The state of tech 2026 is best amplified by "The company travel booking tool keeps randomly redirecting to Microsoft Copilot 365 because something in the SSO is broken."

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 14/04/2026

Time since the last timezone bug: -2 hours.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 14/03/2026

There's a reason that in German you don't check your bag, you do "Gepäck aufgeben", which literally means "give up your bag".

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 14/03/2026

Apparently, even though you are at an airport, your checked bags are somewhere on a conveyor belt at the airport, and you have a rebooked flight to your destination, there's nothing the baggage tracking office can do to ensure that your bag also makes it to the destination on that flight. You […]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 13/03/2026

The big three US airlines are United, Delta, and American. Missed opportunity for Delta to call itself States.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 11/03/2026

RE: mastodon.social/@Sdowney/1162102843… And I'll be talking about allternatives, contravariant functors, and lenses!

mastodon.social

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Niki @nikitonsky.mastodon.online.ap.brid.gy · 03/03/2026

Gotta give it to Claude Code developers: they are exceptionally brave. I would’ve been straight up embarrassed to show stats like this. Reminder: Claude Code is a thin CLI client that reads input from your terminal, sends it to Antrhopic servers and prints back the response.

Tweet by @trq212 about Claude Code rendering scene graph in 11 ms and printing it to terminal in 5 ms

Tweet by @jarredsumner about Claude Code memory usage growing from 10 Gb in January to 68 Gb to 1.7 Gb now

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 16/02/2026

@pervognsen I watched a talk once where the speaker asked for questions and said "and remember: a question is when you want more information from me".

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 19/12/2025

Reddit blog post discussing a problem. Commenter A: Can't you just do X? Commenter B:: No, because Y. Commenter A: But if you do X, then Z happens, so Y shouldn't be an issue. I didn't read the blog post. Commenter B: As the blog post explains, Z does not happen!

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 08/11/2025

Achievement unlocked: if consteval { if constexpr (foo) { if (bar) { throw error; } } }

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dgelessus @dgelessus.mastodon.social.ap.brid.gy · 05/11/2025

when compiling C code, enable the -fPIE option to compile to Proto-Indo-European, for maximum compatibility with all CPU architectures developed on the Eurasian continent

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 05/11/2025

From the standardization committee that brought you keywords such as `co_return`, `decltype`, and `reinterpret_cast`, now for your consideration: `trivially_relocatable_if_eligible` and `replacable_if_eligible`! C++ - you're gonna need a bigger column limit.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 22/10/2025

I'm hoping a cobus is enough like a bus in that it gets me to my destination.

Photo of a sign in a bus saying the name of the manufacturer/model:

cobus 3000

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Markus Werle @markuswerle.nrw.social.ap.brid.gy · 28/08/2025

As co-organizer of the C++ User Group #Aachen, I am thrilled to announce our program for next Wednesday, September 3, 2025. We will meet at SLB starting at 6:30 p.m., and the talks will begin at 7:00 p.m.. If possible, please pre-register at […] [Original post on nrw.social]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 21/08/2025

However, a) the bitcode is bit-aligned, not byte aligned, so the slice is more awkward than necessary, and b) the first entry of the type block needs to specify the number of entries in the byte block. This is encoded as a variable length integer. So after you've encoded all the types and now […]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 21/08/2025

LLVM bitcode is not good designed if you want to generate it efficiently. For example, you need to define all types that a module is using without duplicates. This is easily done with a hash table and ideally you could use the binary serialization as key: Serialize into a buffer, do lookup in […]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 19/08/2025

Another day, another #if 0 ... #endif bisect to find the code that crashes MSVC.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 17/08/2025

Got tired of linking with LLVM so I've written something to emit bitcode directly. The blocks and records are conveniently defined in a little X macro file which then is used to stamp out a fully type safe builder API.

X Macro definition file:

//=== identification block ===//
LLVM_BC_DEFINE_BLOCK (IDENTIFICATION, 13)

LLVM_BC_DEFINE_RECORD (IDENTIFICATION, STRING, 1, (String, str))
LLVM_BC_DEFINE_RECORD (IDENTIFICATION, EPOCH, 2, (llvm_BcEpoch, epoch))

//=== module block ===//
LLVM_BC_DEFINE_BLOCK(MODULE, 8)

LLVM_BC_DEFINE_RECORD (MODULE, VERSION, 1, (llvm_BcModuleVersion, version))
LLVM_BC_DEFINE_RECORD (MODULE, SOURCE_FILENAME, 16, (String, name))

$Usage example of the API: auto identification = llvm_bc_block(IDENTIFICATION, ctx, memory.task); { llvm_bc_record( IDENTIFICATION_STRING, ctx, identification, memory.task, .str = zstring("my-producer") ); llvm_bc_record( IDENTIFICATION_EPOCH, ctx, identification, memory.task, .epoch = LLVM_BC_EPOCH ); } auto module = llvm_bc_block(MODULE, ctx, memory.task); { llvm_bc_record(MODULE_VERSION, ctx, module, memory.task, .version = LLVM_BC_MODULE_VERSION); llvm_bc_record(MODULE_SOURCE_FILENAME, ctx, module, memory.task, .name = zstring("input")); } llvm_bitcode(ctx, memory.task, identification, module, out);$

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maybeanerd @maybeanerd.bumscode.com.ap.brid.gy · 11/07/2025

Enjoyed the talk by @foonathan at #weAreDevelopers on how to do functional programming in C++ a lot I don't even use C++, but it was so well presented that I felt I still understood

Jonathan on stage answering questions from the aduience

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 02/07/2025

Today I rebased my stuff after spending two weeks on conferences only to discover that we've introduced an `use_iter_move_on_xvalue_dereference_index` customization point.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 23/06/2025

Can anybody I know invite me to lobste.rs?

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Christian Lawson-Perfect @christianp.mathstodon.xyz.ap.brid.gy · 29/05/2025

When you finish writing your parser

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 24/04/2025

I love how fixing audio issues on various linux devices has become as simple as `pacman -S pipewire-pulse` or `pacman -S pipewire-alsa`.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 24/04/2025

Next week, I'm going to be attending C++Now, and I'm going to be giving my two favorite talks of all time: First, a repeat of my "Overenginering max(a, b)" talk, which is just a bunch of fun metaprogramming to solve a safety problem. Then, a new talk "Missing (and future?) range concepts" […]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 09/03/2025

For example, I have an X macro file containing stuff like DATA(Foo, (int, a), (float, f)) which generates both struct definitions and JSON serialization code of the form: json_object_begin(out); json_object_key(out, "a"); json_int(out, foo.a); json_object_key(out, "b"); json_float(out, foo […]

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 09/03/2025

And of course, I'm utterly abusing X macros, preprocessor tricks, and _Generic. Because a good C++ programmer, can write C++ in any language.

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Jonathan Müller @foonathan.fosstodon.org.ap.brid.gy · 09/03/2025

I've been programming in C for a small project, a couple of thoughts: * -Wimplicit-fallthrough isn't enabled by -Wall -Wextra in clang, which has bitten me. * I got tired of `Foo foo = (foo)x`, so I'm using C23 and auto, sorry, not sorry. * I spend a lot less time thinking about interface […]

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