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GCC 5.1 released

gcc.gnu.org

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Re: GCC 5.1 released

#11

Post by halosghost »

thoughtpolice wrote: post #7
halosghost wrote: post #2

Some of these are terrific changes! E.g., OpenMP 4.0 and Cilk Plus support, wew! I also love that ``gcc`` now defaults to ``-std=gnu11`` instead of ``-std=gnu89``; what a huge step forward! But, there were a couple of things in here that I was hoping to see but did not find (namely, it seems gcc still does not have ``-Weverything``). While I am glad to see gcc making progress, I feel bound to clang until gcc's warnin…

GCC 5.1 defaults to having color diagnostics set to `auto`, meaning it will display nice, beautiful diagnostics like Clang does on your terminal, if that's what you're referring to. (You can also get these with GCC 4.9, too, using the `GCC_COLORS` environment variable). Personally I don't care about that as much as the optimization improvements this time arond, it seems. Better devirtualization? AutoFDO? Reuse of the…

Haha, I wasn't actually referring to colored warning/error output (though it is a nice plus!). I was mostly referring to `clang`'s `-Weverything` and the absence of any such alias for `gcc`.

Re: GCC 5.1 released

#12

Post by cremno »

ploxiln wrote: post #9

I won't be able to use them in portable code anytime soon, but the new feature here that most interests me is __builtin_add_overflow, __builtin_sub_overflow and __builtin_mul_overflow "These builtins have two integral arguments (which don't need to have the same type), the arguments are extended to infinite precision signed type, +, - or * is performed on those, and the result is stored in an integer variable pointed…

Sadly clang (the origin of those built-in functions) doesn't implement the type-generic ones and GCC doesn't implement __has_builtin yet.

Re: GCC 5.1 released

#13

Post by BinaryIdiot »

halosghost wrote: post #2

Some of these are terrific changes! E.g., OpenMP 4.0 and Cilk Plus support, wew! I also love that ``gcc`` now defaults to ``-std=gnu11`` instead of ``-std=gnu89``; what a huge step forward! But, there were a couple of things in here that I was hoping to see but did not find (namely, it seems gcc still does not have ``-Weverything``). While I am glad to see gcc making progress, I feel bound to clang until gcc's warnin…

> namely, it seems gcc still does not have ``-Weverything``

I would love to have a -Weverything; as a fairly rusty C++ dev I originally thought -Wall was supposed to have, you know, all but was pretty surprised to learn it didn't actually contain all. It would be great if they deprecated -Wall and made it so -Weverything always did all warnings (including any newly introduced warnings).

Re: GCC 5.1 released

#14

Post by Someone »

ploxiln wrote: post #9

I won't be able to use them in portable code anytime soon, but the new feature here that most interests me is __builtin_add_overflow, __builtin_sub_overflow and __builtin_mul_overflow "These builtins have two integral arguments (which don't need to have the same type), the arguments are extended to infinite precision signed type, +, - or * is performed on those, and the result is stored in an integer variable pointed…

That may be sooner than you think, depending on what you mean by portable. I think these functions originated as non-generic versions in clang (http://clang.llvm.org/docs/LanguageExtensions.html#builtin-f...). gcc copied them and now added generic variants. I think it is likely that clang will now copy gcc and add the generic variants.

Edit: here is the request for gcc to copy clang: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59708 (nice discussion about the need to have builtins for overflow detection)

And here is a request for clang to copy gcc's generic versions: https://llvm.org/bugs/show_bug.cgi?id=21716

Re: GCC 5.1 released

#15

Post by jeorgun »

BinaryIdiot wrote: post #13
halosghost wrote: post #2

Some of these are terrific changes! E.g., OpenMP 4.0 and Cilk Plus support, wew! I also love that ``gcc`` now defaults to ``-std=gnu11`` instead of ``-std=gnu89``; what a huge step forward! But, there were a couple of things in here that I was hoping to see but did not find (namely, it seems gcc still does not have ``-Weverything``). While I am glad to see gcc making progress, I feel bound to clang until gcc's warnin…

> namely, it seems gcc still does not have ``-Weverything`` I would love to have a -Weverything; as a fairly rusty C++ dev I originally thought -Wall was supposed to have, you know, all but was pretty surprised to learn it didn't actually contain all. It would be great if they deprecated -Wall and made it so -Weverything always did all warnings (including any newly introduced warnings).

Clang's -Weverything isn't really as useful as it sounds; since it includes fairly-to-completely useless warnings like -Wc++98-compat, -Wpadded, or -Wweak-vtables, you'll end up spending so much time playing warning whack-a-mole that you might as well have not enabled the thing in the first place. At least that's been my experience.

Re: GCC 5.1 released

#17

Post by halosghost »

BinaryIdiot wrote: post #13
halosghost wrote: post #2

Some of these are terrific changes! E.g., OpenMP 4.0 and Cilk Plus support, wew! I also love that ``gcc`` now defaults to ``-std=gnu11`` instead of ``-std=gnu89``; what a huge step forward! But, there were a couple of things in here that I was hoping to see but did not find (namely, it seems gcc still does not have ``-Weverything``). While I am glad to see gcc making progress, I feel bound to clang until gcc's warnin…

> namely, it seems gcc still does not have ``-Weverything`` I would love to have a -Weverything; as a fairly rusty C++ dev I originally thought -Wall was supposed to have, you know, all but was pretty surprised to learn it didn't actually contain all. It would be great if they deprecated -Wall and made it so -Weverything always did all warnings (including any newly introduced warnings).

The only problem I have with keeping `-Wall` is that it's misleading. But, other than that, I don't mind keeping it around so long as there is an option that enables all warnings. And since 5.1 includes a few more fancy new warnings, it'd be great to see those added into this hypothetical `-Weverything` as well. But, the issue on their bugtracker for inclusion of this feature was opened during 4.8 and still hasn't been confirmed for a release to target… makes me SadInside™.

Re: GCC 5.1 released

#18

Post by halosghost »

jeorgun wrote: post #15
BinaryIdiot wrote: post #13

Earlier quoted context omitted.

> namely, it seems gcc still does not have ``-Weverything`` I would love to have a -Weverything; as a fairly rusty C++ dev I originally thought -Wall was supposed to have, you know, all but was pretty surprised to learn it didn't actually contain all. It would be great if they deprecated -Wall and made it so -Weverything always did all warnings (including any newly introduced warnings).

Clang's -Weverything isn't really as useful as it sounds; since it includes fairly-to-completely useless warnings like -Wc++98-compat, -Wpadded, or -Wweak-vtables, you'll end up spending so much time playing warning whack-a-mole that you might as well have not enabled the thing in the first place. At least that's been my experience.

I completely disagree. It's true that some of the warnings it enables aren't terribly useful, but being able to enable all warnings is very helpful instead of having to manually list ~40 flags. Additionally, -Wpadded and the like are actually helpful for optimizations.

Plus, writing code (in C, I cannot speak for Cxx) which results in no warning output from `-Weverything` is actually not that difficult to do, and generally the result is that you've written more robust code in the process. A lot of projects are now trying to move to compile with `-Weverything` and not disable any warnings, and I personally think it's a great move.

Re: GCC 5.1 released

#20

Post by jeorgun »

halosghost wrote: post #18
jeorgun wrote: post #15

Earlier quoted context omitted.

Clang's -Weverything isn't really as useful as it sounds; since it includes fairly-to-completely useless warnings like -Wc++98-compat, -Wpadded, or -Wweak-vtables, you'll end up spending so much time playing warning whack-a-mole that you might as well have not enabled the thing in the first place. At least that's been my experience.

I completely disagree. It's true that some of the warnings it enables aren't terribly useful, but being able to enable all warnings is very helpful instead of having to manually list ~40 flags. Additionally, -Wpadded and the like are actually helpful for optimizations. Plus, writing code (in C, I cannot speak for Cxx) which results in no warning output from `-Weverything` is actually not that difficult to do, and gen…

For C, I'd agree that it's useful. The flags I listed have issues specifically for C++. -Wc++98-compat, on a C++11 or C++14 project, is about as helpful as you'd expect. -Wpadded is triggered pretty reliably by subclassess. And so forth.

Of course it is possible to specifically disable useless warnings, but in my experience it's just as easy to add a reasonable selection of flags (say, -Wall -Wextra -Wold-style-cast -Wconversion -Wsign-conversion) than to start with -Weverything and work backwards. Still, it has been some time since I've tried using it; maybe I ought to give it another chance.

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