Allegro.cc - Online Community

Allegro.cc Forums » Allegro Development » Allegro 5.0.11 released!

This thread is locked; no one can reply to it. rss feed Print
 1   2 
Allegro 5.0.11 released!
Gideon Weems
Member #3,925
October 2003

SiegeLord said:
#define ALLEGRO_UNSTABLE
#include <allegro5/allegro.h>

This is a really, really good idea.

When you think about it, the implementation is the same as DEPRECATED warnings.

Edgar Reynaldo
Member #8,592
May 2007
avatar

Gideon Weems said:

SiegeLord said:

#define ALLEGRO_UNSTABLE
#include <allegro5/allegro.h>

This is a really, really good idea.

Hmm, I don't know if I agree. Wouldn't that mean that the allegro source would be littered with a bunch of #ifdefs around every single difference between the stable and 'unstable' branches? It sounds like it would lead to a maintenance and compilation nightmare to me.

SiegeLord
Member #7,827
October 2006
avatar

When you think about it, the implementation is the same as DEPRECATED warnings.

I do want a ALLEGRO_NO_DEPRECATED as well :P.

Hmm, I don't know if I agree. Wouldn't that mean that the allegro source would be littered with a bunch of #ifdefs around every single difference between the stable and 'unstable' branches? It sounds like it would lead to a maintenance and compilation nightmare to me.

This'd just affect the headers. I'm thinking ALLEGRO_FUNC and ALLEGRO_UNSTABLE_FUNC. Either way, there wouldn't be a 'no unstable features' CMake option or anything.

"For in much wisdom is much grief: and he that increases knowledge increases sorrow."-Ecclesiastes 1:18
[SiegeLord's Abode][Codes]:[DAllegro5]:[RustAllegro]

Thomas Fjellstrom
Member #476
June 2000
avatar

How do you expect to handle ABI compatibility? Especially when "unstable" things are removed or renamed?

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

SiegeLord
Member #7,827
October 2006
avatar

Don't know yet... maybe all of this is impossible :P.

"For in much wisdom is much grief: and he that increases knowledge increases sorrow."-Ecclesiastes 1:18
[SiegeLord's Abode][Codes]:[DAllegro5]:[RustAllegro]

Thomas Fjellstrom
Member #476
June 2000
avatar

I thought it'd might be possible to somehow split the unstable features into a separate optional library... Not sure if that is possible if they share the same source file. Maybe some clever linker scripts?

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

beoran
Member #12,636
March 2011

For C a stable ABI can be achieved by not changing the parameters to functions and only adding new members to structs, not removing or reordering them. That means once a function is declared to be a stable API, it can't change it's parameters anymore nor may it be removed. But with some #define preprocessor tricks this can be remedied easily enough.

It would very well be possible to do this with what SiegeLord proposes.

Chris Katko
Member #1,881
January 2002
avatar

How do you expect to handle ABI compatibility? Especially when "unstable" things are removed or renamed?

I'm not a dev, so maybe you're talking about internally. But if you mean externally, I see no reason people should expect an "unstable" function never to change. The same way between the existing two branches.

[edit]

But it looks like you're talking about internals. What's the problem this introduces? If you've got, say, a DLL, and you add a new function, do all the other functions get moved around and broken? Surely dynamic libraries work on a function name level and not a byte offset?

I guess in the case of a compiled program, but the DLL ABI changes, "function name exists but was changed" or "you are calling a depreciated unstable function". But couldn't we introduce some boilerplate for those rare cases, where we have a list of functions that immediately flag a critical-level allegro error that says, "This program is calling a depreciated function. There has likely been a DLL version mismatch."

Additionally, since we'd be forcing people to use ALLEGRO_UNSTABLE, it's the developer's fault if they make the assumption that functions will never change and doesn't statically link, or provide updates.

[edit]

Doing some reading. This seems like a fairly good attempt at C++ ABI, if you're wanting something to read for fun.

Basically, they use extern "abi" {}, and the OS (not the compiler) defines how that section must be implemented. And to deal with std::library issues (std::vector is a huge issue that can't even be used in public library functions), they introduce std::abi::library functions which are binary stable.

-----sig:
“Programs should be written for people to read, and only incidentally for machines to execute.” - Structure and Interpretation of Computer Programs

Thomas Fjellstrom
Member #476
June 2000
avatar

But it looks like you're talking about internals. What's the problem this introduces?

I was talking more about the dll's or so's themselves. But it doesn't seem to be a problem. At most we'll have to worry about public types that are allocated statically (ie: ALLEGRO_COLOR, but why would that change all that often?)

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

beoran
Member #12,636
March 2011

@Chris Katco:

That's an unimplemented proposal for C++ which is a huge mess when it comes to a stable ABI due to naùe mangling. Name mangling of C++ is the reason why there is ,no stable ABI and slower dll loading with c++. Plain C doesn't have any of those problems to keep the ABI stable when you stick to a few basic rules. Another reason why plain C is better. :)

Chris Katko
Member #1,881
January 2002
avatar

beoran said:

That's an unimplemented proposal for C++ which is a huge mess when it comes to a stable ABI due to naùe mangling.

Yes, yes. But a man can dream, can't he? ;)

-----sig:
“Programs should be written for people to read, and only incidentally for machines to execute.” - Structure and Interpretation of Computer Programs

SiegeLord
Member #7,827
October 2006
avatar

So I checked Linux GCC, Windows GCC (via MinGW) and MSVC, and they all support the general ABI idea I was going for. Basically, if your program doesn't use a function from a shared library, then the next version of the library can safely remove that function without breaking ABI compatibility. So if you compile your code without ALLEGRO_UNSTABLE in e.g. 5.2.0, then your code will continue to work with DLLs produced for any later 5.2.x version. If you do use ALLEGRO_UNSTABLE, then your program is only guaranteed to work with the very same version your compiled for (i.e. 5.2.0 in this example).

This is the same ABI guarantee we currently provide with the current dual branch arrangement. Code compiled with 5.0.x works with shared libraries with version 5.0.y where y >= x. Code compiled with 5.1.x works only with shared libraries with the same version.

It occurs to me that we could actually provide an option to build Allegro without any visible unstable entries, for things like Debian which might not like these unstable ABI breakages.

"For in much wisdom is much grief: and he that increases knowledge increases sorrow."-Ecclesiastes 1:18
[SiegeLord's Abode][Codes]:[DAllegro5]:[RustAllegro]

Gideon Weems
Member #3,925
October 2003

A cursory search reveals that gstreamer has done this for years.

SiegeLord
Member #7,827
October 2006
avatar

A cursory search reveals that gstreamer has done this for years.

Hah, great. Although I still prefer my opt-in approach more than silencing a warning. I get the impression many people routinely turn a blind eye to warnings :P.

"For in much wisdom is much grief: and he that increases knowledge increases sorrow."-Ecclesiastes 1:18
[SiegeLord's Abode][Codes]:[DAllegro5]:[RustAllegro]

Gideon Weems
Member #3,925
October 2003

Yeah, I get that impression, too. ;D Besides, opting-in feels more appropriate.

Re #allegro: Apparently, __declspec(deprecated) is the deprecated macro for MSVC. I don't have MSVC, so I can't test it.

Edit: Hehe, I think you may have already found the Stack Overflow post...

 1   2 


Go to: