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GCC 16 considering changing default to C++20

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Re: GCC 16 considering changing default to C++20

#41

Post by superkuh »

withzombies wrote: post #10

Shouldn't the compilers be on the bleeding edge of the standards? What is the downside of switching to the newest standard when it's properly supported? It's the type of dog fooding they should be doing! It's one reason why people care so much about self-hosted compilers, it's a demonstration of maturity of the language/compiler.

When a language changes significantly faster than release cycles (ie, rust being a different compiler every 3 months) it means that distros cannot self-host if they use rust code in their software. ie, with Debian's Apt now having rust code, and Debian's release cycle being 4 years for LTS, Debian's shipped rustc won't be able to compile Apt since nearly all rust devs are bleeding edge targeters. The entire language culture is built around this rapid improvement.

I love that C++ has a long enough time between changing targets to actually be useful and that it's culture is about stability and usefulness for users trying to compile things rather than just dev-side improvements uber alles.

Re: GCC 16 considering changing default to C++20

#42

Post by renewiltord »

veltas wrote: post #6
NegativeK wrote: post #4

Earlier quoted context omitted.

Anubis has been around for almost a year now, but it's also not particularly relevant to the content of the email thread.

It's particularly jarring to basically every site I've seen it on which is usually some serious and professional looking open source site. I wonder why nobody configures this, is this not something that they can configure themselves to a more relevant image, like the GCC logo or something?

I’m sure if you want you can offer to pay like $500/mo on their behalf and they’ll change it for everyone.

Re: GCC 16 considering changing default to C++20

#43

Post by cogman10 »

rmu09 wrote: post #39
cogman10 wrote: post #17

Earlier quoted context omitted.

There's a bootstrapping process that has to happen to compile the compiler. Moving up the language standard chain requires that compilers compiling the compiler need to also migrate up the chain. So you can never be perfectly bleeding edge as it'd keep you from being able to build your compiler with an older compiler that doesn't support those bleeding edge features. Imagine, for example, that you are debian and you…

Aren't they talking about the c++ dialect the compiler expects without any further -std=... arguments? How does that affect the bootstrapping process? This https://gcc.gnu.org/codingconventions.html should define what C/C++ standard is acceptable in the GCC.

The way I read withzombies's comment (and it could be wrong) was they were talking about the language version of the compilers source. I assumed that from the "dogfooding" portion of the comment.

Re: GCC 16 considering changing default to C++20

#44

Post by kstrauser »

cogman10 wrote: post #17
withzombies wrote: post #10

Shouldn't the compilers be on the bleeding edge of the standards? What is the downside of switching to the newest standard when it's properly supported? It's the type of dog fooding they should be doing! It's one reason why people care so much about self-hosted compilers, it's a demonstration of maturity of the language/compiler.

There's a bootstrapping process that has to happen to compile the compiler. Moving up the language standard chain requires that compilers compiling the compiler need to also migrate up the chain. So you can never be perfectly bleeding edge as it'd keep you from being able to build your compiler with an older compiler that doesn't support those bleeding edge features. Imagine, for example, that you are debian and you…

Counterpoint: you could write a C++ compiler in a non-C/C++ language such that the compiler’s implementation language doesn’t even have the notion of C++20.

A compiler is perfectly capable of compiling programs which use features that its own source does not.

Re: GCC 16 considering changing default to C++20

#45

Post by cogman10 »

stabbles wrote: post #40
cogman10 wrote: post #17

Earlier quoted context omitted.

There's a bootstrapping process that has to happen to compile the compiler. Moving up the language standard chain requires that compilers compiling the compiler need to also migrate up the chain. So you can never be perfectly bleeding edge as it'd keep you from being able to build your compiler with an older compiler that doesn't support those bleeding edge features. Imagine, for example, that you are debian and you…

This is not the case. They are discussing the default value of `g++ -std=...`. That does not complicate bootstrapping as long as the C++ sources of GCC are compatible with older and newer versions of the C++ standard.

> as long as the C++ sources of GCC are compatible with older and newer versions of the C++ standard.

I've worked on a number of pretty large projects. If the target for the source code changes it can be really hard to keep C++20 features from creeping in. It means that you either need to explicitly build targeting 11, or whoever does code reviews needs to have encyclopedic knowledge of whether or not a change leaked in a future feature.

It is "doable" but why would you do it when you can simply keep the compiler targeting 11 and let it do the code review for you.

Re: GCC 16 considering changing default to C++20

#46

Post by suby »

whobre wrote: post #32
jjmarr wrote: post #2

Good. Let me use modules!

Seriously, why? They are broken. https://vector-of-bool.github.io/2019/01/27/modules-doa.html

This is from 2019, prior to the finalization of modules in the standard. I'd be interested in how many of these issues were unaddressed in the final version shipped.

Re: GCC 16 considering changing default to C++20

#47

Post by cxr »

kstrauser wrote: post #44
cogman10 wrote: post #17

Earlier quoted context omitted.

There's a bootstrapping process that has to happen to compile the compiler. Moving up the language standard chain requires that compilers compiling the compiler need to also migrate up the chain. So you can never be perfectly bleeding edge as it'd keep you from being able to build your compiler with an older compiler that doesn't support those bleeding edge features. Imagine, for example, that you are debian and you…

Counterpoint: you could write a C++ compiler in a non-C/C++ language such that the compiler’s implementation language doesn’t even have the notion of C++20. A compiler is perfectly capable of compiling programs which use features that its own source does not.

That's not a counterpoint—at least not to anything in the comment that you're (nominally) "responding" to.

So why has it been posted it as a reply, and why label it a counterpoint?

Re: GCC 16 considering changing default to C++20

#48

Post by [deleted] »

suby wrote: post #8
f1refly wrote: post #5

Earlier quoted context omitted.

Right? I hope it never goes away, we should make the web more fun instead of sad and clean!

I think if you were to poll people, a significant portion would be repulsed by this catgirl aesthetic, or (though this isn't the case for Anubis) the cliche inappropriately dressed inappropriately young anime characters dawned as mascots in an ever increasing number of projects. People can do whatever they want with their projects, but I feel like the people who like this crap perhaps don't understand how repulsive i…

[deleted]

Re: GCC 16 considering changing default to C++20

#49

Post by quietbritishjim »

cogman10 wrote: post #45
stabbles wrote: post #40

Earlier quoted context omitted.

This is not the case. They are discussing the default value of `g++ -std=...`. That does not complicate bootstrapping as long as the C++ sources of GCC are compatible with older and newer versions of the C++ standard.

> as long as the C++ sources of GCC are compatible with older and newer versions of the C++ standard. I've worked on a number of pretty large projects. If the target for the source code changes it can be really hard to keep C++20 features from creeping in. It means that you either need to explicitly build targeting 11, or whoever does code reviews needs to have encyclopedic knowledge of whether or not a change leaked…

> ... why would you do it when you can simply keep the compiler targeting 11 ...

It doesn't appear to me that the parent comment was implying otherwise.

The default is changing for any compilation that doesn't explicitly specify a standard version. I would have thought that the build process for a compiler is likely careful enough that it does explicitly specify a version.

Re: GCC 16 considering changing default to C++20

#50

Post by cogman10 »

quietbritishjim wrote: post #49
cogman10 wrote: post #45

Earlier quoted context omitted.

> as long as the C++ sources of GCC are compatible with older and newer versions of the C++ standard. I've worked on a number of pretty large projects. If the target for the source code changes it can be really hard to keep C++20 features from creeping in. It means that you either need to explicitly build targeting 11, or whoever does code reviews needs to have encyclopedic knowledge of whether or not a change leaked…

> ... why would you do it when you can simply keep the compiler targeting 11 ... It doesn't appear to me that the parent comment was implying otherwise. The default is changing for any compilation that doesn't explicitly specify a standard version. I would have thought that the build process for a compiler is likely careful enough that it does explicitly specify a version.

> It's the type of dog fooding they should be doing! It's one reason why people care so much about self-hosted compilers, it's a demonstration of maturity of the language/compiler.

I could be misreading this, but unless they have a different understanding of what it means to dog fooding than I do then it seems like the proposal is to use C++20 features in the compiler bootstraping.

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