It's worth celebrating (well, noting in an approving manner) this release. GCC is a foundation stone project for, well, a huge amount of the world's wealth.
It is a healthy project (even with CLang etc), and with the heartbleed post mortem on our minds we should probably ask what can be done to keep it and others healthy - auditing, foundation status etc.
So thank you GCC developers, for making sure I do not need to worry about something.
Re:GCC 5.2 released
by agwa on Thursday July 16, 2015 @11:37AM
(#9897851)
It's worth noting that, due to GCC's new and esoteric version numbering scheme[1], this is a bugfix-only release on the 5.x branch. The bigger news was when GCC 5.1 (a major stable release) was released in April. That said, GCC 5.2 fixes a pretty serious bug that I was hitting so I'm happy to hear about it!
Re:GCC 5.2 released
by 3JPLW on Thursday July 16, 2015 @01:53PM
(#9898784)
Woah, new and esoteric indeed!
X.0.0 is experimental development
X.0.1 is pre-release stabilization stage
X.1.0 is the stable release
X.1.1 is development of release branch (fixes and backports)
X.2.0 is the second stable release
It looks like only X.1.0, X.2.0, etc uniquely tag a single point in the development history. Are all the others just moving labels?
Re:GCC 5.2 released
by pcwalton on Thursday July 16, 2015 @03:34PM
(#9899405)
I assume it means globals, which is significantly less trivial. Any SSA-based compiler, which GCC has been for years and years, trivially does this for locals.
Re:GCC 5.2 released
by greglindahl on Thursday July 16, 2015 @12:46PM
(#9898330)
This is a standard compiler feature, yes -- lots of real code out there has a lot of dead writes, such as debugging code that has been only partly removed or disabled. Historically, it's been a significant win for some of the SPECcpu benchmarks.
Re:GCC 5.2 released
by astrange on Thursday July 16, 2015 @08:53PM
(#9900794)
It's standard to remove local variables that are write-only, but globals aren't always defined to be unused even when you want them to be. If you're building a shared library and you exported the symbol, it has to leave it in as part of the API.
Link-time optimization can delete a lot more stuff when you're building a program directly, since it only has to keep main()… as long as you didn't go and use things like function pointers.
This is one reason I try to use '-fvisibility=hidden' in libraries, because it prevents anything from being part of the API unless you go back and specifically export it.
Re:GCC 5.2 released
by greglindahl on Thursday July 16, 2015 @04:40PM
(#9899760)
No, because no one ever reads the dead data. These are not microbenchmarks that get broken by optimizations like this; SPECcpu programs have answers, and the goal is to output the answer. The answer is tested. Anything you can delete from the program is fair game.
Re:GCC 5.2 released
by RoboSeldon on Thursday July 16, 2015 @11:09AM
(#9897667)
gfortran which is part of GCC supports modules (this is because Fortran the language supports modules).
If you meant modules for C or C++, no (as far as I know), probably because C and C++ have no standard for modules. In a recent talk Bjarne Stroustroup talks about his hope that C++17 will include support for modules https://www.youtube.com/watch?v=2egL4y_VpYg
Re:GCC 5.2 released
by bsdetector on Thursday July 16, 2015 @12:43PM
(#9898316)
I'm more interested in why GCC still doesn't have a D frontend.
Back when people were criticizing Google for acquiring GCC developers and then adding their own Go language I think they promised to add D in like 4.6 or something like that.
Re:GCC 5.2 released
by rossy on Thursday July 16, 2015 @07:34PM
(#9900520)
If you're using MSYS2 to get your MinGW compilers, the package has been updated, but you won't see builds on the mirrors until all the other packages have been rebuilt for GCC 5.1/5.2 (due to the ABI change.)
It is a healthy project (even with CLang etc), and with the heartbleed post mortem on our minds we should probably ask what can be done to keep it and others healthy - auditing, foundation status etc.
So thank you GCC developers, for making sure I do not need to worry about something.
[1] https://gcc.gnu.org/develop.html#num_scheme
That's probably something one should keep in mind when writing micro-benchmarks.
Link-time optimization can delete a lot more stuff when you're building a program directly, since it only has to keep main()… as long as you didn't go and use things like function pointers.
This is one reason I try to use '-fvisibility=hidden' in libraries, because it prevents anything from being part of the API unless you go back and specifically export it.
But doesn't it mean that you're not really executing the full benchmark then?
If you meant modules for C or C++, no (as far as I know), probably because C and C++ have no standard for modules. In a recent talk Bjarne Stroustroup talks about his hope that C++17 will include support for modules https://www.youtube.com/watch?v=2egL4y_VpYg
EDIT: I'm wrong. That was GCC 5.1.
Back when people were criticizing Google for acquiring GCC developers and then adding their own Go language I think they promised to add D in like 4.6 or something like that.
https://github.com/Alexpux/MINGW-packages/commit/a6a16a3
Does the LLVM+Clang combo make GCC obsolete?