Extend compiler_version.py to work with clang output.

compiler_version.py now tries multiple different command lines. This is needed as clang needs either -no-integrated-as or -fno-integrated-as and gcc supports neither (Mac OS X linker/assembler also needs -v rather than --version).

compiler_version.py now understands CXXFLAGS too. This means that if the linker/assembler used is changed by the environment value it will still be found (Such as when adding -B argument.) This will be helpful for using binutils from third_party.

Also adding unittests for compiler_version.py tool. Checks a bunch of known version strings, more can be added as they are discovered. Could also help extending to Mac OS
X in the future.

BUG=352046

[mithro-old, 2014-03-24 05:36:26]

Hi!

This change is needed before I can reland
https://codereview.chromium.org/199333007/.

The tests in this change should also help prevent the issue caused in
https://codereview.chromium.org/207303004/.

Tim

[Nico, 2014-03-24 09:20:44]

This script is getting pretty complicated pretty quickly. Is all this needed? We
don't really care about the compiler version for the fission stuff, right? (And
we only care about the compiler version for gcc, too.) Can you ask as instead of
gcc for the version for binutils? Making this work with clang seems like it's
not really needed at this point, since we only care about the version of the
tools clang execs behind the scenes.

[mithro-old, 2014-03-24 09:51:42]

On 2014/03/24 09:20:44, Nico (on GMT time Mar 15 - 24) wrote:
> This script is getting pretty complicated pretty quickly.

I agree.

> Is all this needed?

Good question, I think it all is, but not 100% confident.

> We don't really care about the compiler version for the fission stuff, right?

You need a modern gcc (>=4.8) or clang (clang >= r174349, still trying to track
down what version that maps to) to support debug fission.

> (And we only care about the compiler version for gcc, too.) 

At the moment we are just assuming that if you are using clang then your version
is new enough. This is okay as long as the clang you are using is alway from
third_party/llvm-build/bin.

> Can you ask as instead of gcc for the version for binutils?

I'm not 100% confident that asking gcc for which version of binutils it'll use
will be the same as the version clang would use.

> Making this work with clang seems like it's not really
> needed at this point, since we only care about the version
> of the tools clang execs behind the scenes.

gcc on Ubuntu Precise is too old to support Debug Fission. We need both
clang+binutils from third_party to enable Debug Fission for people on that
platform (all Googlers).

[mithro-old, 2014-03-26 02:15:53]

Friendly ping.

Tim

[Nico, 2014-03-26 02:18:30]

On 2014/03/24 09:51:42, mithro wrote:
> On 2014/03/24 09:20:44, Nico (on GMT time Mar 15 - 24) wrote:
> > This script is getting pretty complicated pretty quickly.
> 
> I agree.
> 
> > Is all this needed?
> 
> Good question, I think it all is, but not 100% confident.
> 
> > We don't really care about the compiler version for the fission stuff,
right?
> 
> You need a modern gcc (>=4.8) or clang (clang >= r174349, still trying to
track
> down what version that maps to) to support debug fission.
> 
> > (And we only care about the compiler version for gcc, too.) 
> 
> At the moment we are just assuming that if you are using clang then your
version
> is new enough. This is okay as long as the clang you are using is alway from
> third_party/llvm-build/bin.

Correct. We don't support building with other clangs.

> > Can you ask as instead of gcc for the version for binutils?
> 
> I'm not 100% confident that asking gcc for which version of binutils it'll use
> will be the same as the version clang would use.
> 
> > Making this work with clang seems like it's not really
> > needed at this point, since we only care about the version
> > of the tools clang execs behind the scenes.
> 
> gcc on Ubuntu Precise is too old to support Debug Fission. We need both
> clang+binutils from third_party to enable Debug Fission for people on that
> platform (all Googlers).

With "this", I meant this script, not fission. For clang, we can just assume
that it's new enough since clang means "chromium's clang" (which is new enough).

[mithro-old, 2014-03-26 02:29:07]

> > At the moment we are just assuming that if you are using clang then your
> version
> > is new enough. This is okay as long as the clang you are using is alway from
> > third_party/llvm-build/bin.
> 
> Correct. We don't support building with other clangs.

Okay great.

Technically you can set your CXX to clang and things would probably work before
this, but happy to not support that.

> > > Can you ask as instead of gcc for the version for binutils?
> > 
> > I'm not 100% confident that asking gcc for which version of binutils it'll
use
> > will be the same as the version clang would use.
> > 
> > > Making this work with clang seems like it's not really
> > > needed at this point, since we only care about the version
> > > of the tools clang execs behind the scenes.
> > 
> > gcc on Ubuntu Precise is too old to support Debug Fission. We need both
> > clang+binutils from third_party to enable Debug Fission for people on that
> > platform (all Googlers).
> 
> With "this", I meant this script, not fission. For clang, we can just assume
> that it's new enough since clang means "chromium's clang" (which is new
enough).

We still need to ask clang which binutils it is using?

Tim

[Nico, 2014-03-26 02:31:48]

On Tue, Mar 25, 2014 at 7:29 PM, <mithro@mithis.com> wrote:

> > At the moment we are just assuming that if you are using clang then your
>> version
>> > is new enough. This is okay as long as the clang you are using is alway
>> from
>> > third_party/llvm-build/bin.
>>
>
>  Correct. We don't support building with other clangs.
>>
>
> Okay great.
>
> Technically you can set your CXX to clang and things would probably work
> before
> this, but happy to not support that.
>
>
>  > > Can you ask as instead of gcc for the version for binutils?
>> >
>> > I'm not 100% confident that asking gcc for which version of binutils
>> it'll
>>
> use
>
>> > will be the same as the version clang would use.
>> >
>> > > Making this work with clang seems like it's not really
>> > > needed at this point, since we only care about the version
>> > > of the tools clang execs behind the scenes.
>> >
>> > gcc on Ubuntu Precise is too old to support Debug Fission. We need both
>> > clang+binutils from third_party to enable Debug Fission for people on
>> that
>> > platform (all Googlers).
>>
>
>  With "this", I meant this script, not fission. For clang, we can just
>> assume
>> that it's new enough since clang means "chromium's clang" (which is new
>>
> enough).
>
> We still need to ask clang which binutils it is using?
>

Right, but isn't it enough to run `as -v` for that?


>
> Tim
>
> https://codereview.chromium.org/199793014/
>

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[mithro-old, 2014-03-26 02:35:33]

> Right, but isn't it enough to run `as -v` for that?

The "as" that gets run by clang is determined by search path which can be
changed with flags and environment variables, for example -B argument. In fact
we are just about to do that, telling clang to search in
third_party/binutils/xxxx/bin

Tim

[Nico, 2014-03-26 02:38:00]

On 2014/03/26 02:35:33, mithro wrote:
> > Right, but isn't it enough to run `as -v` for that?
> 
> The "as" that gets run by clang is determined by search path which can be
> changed with flags and environment variables, for example -B argument. In fact
> we are just about to do that, telling clang to search in
> third_party/binutils/xxxx/bin

While true, this isn't really relevant to this CL as you're not passing -B to
the compiler either, right? Also, if we pass -B for as, we know binutils will be
new enough and don't need to call this script.

(…afk for a bit)