Allow library entries of the form '-lfoo' on MSVS.

Allow library entries of the form '-lfoo' on MSVS.

This allows libraries to be specified in way that
works on all platforms.


BUG=

Committed: https://code.google.com/p/gyp/source/detail?r=1505

[bradn, 2012-09-21 05:23:47]

Nothing inherently bad, but what's use case?
I mean are there an windows system libs that match posix-y ones?
Maybe I'm missing something.

[Sam Clegg, 2012-09-21 17:44:06]

On 2012/09/21 05:23:47, bradn wrote:
> Nothing inherently bad, but what's use case?
> I mean are there an windows system libs that match posix-y ones?
> Maybe I'm missing something.

Not only system libs.  Our particular use case is that
when building nacl apps we want to link against ppapi_cpp
(and friends) on all platforms.

I can think of many other examples of cross platform libs
that are often distributed in binary from (SDL, libjpeg, etc).
Having a cross platform way to say "use this lib" is surely
a useful thing.  I guess chrome pretty much builds everything
from source so it hasn't come up until now.

TBH, I think the cleanest way to do this kind of thing would
be to mandate that all 'libraries' are just the bare names
and the generators know how to expand them into link args.
e.g:

linux:  'z' -> '-lz'
win32:  'z' -> 'z.lib'

But this change is (hopefully) much less intrusive and will
provide a way to express cross platform libs without breaking
any existing gyp files.

[bradn, 2012-09-21 17:45:09]

Ah, ppapi trusted libraries.
Ok.
LGTM

[Ryan Sleevi, 2012-09-21 18:19:09]

On 2012/09/21 17:44:06, Sam Clegg wrote:
> On 2012/09/21 05:23:47, bradn wrote:
> > Nothing inherently bad, but what's use case?
> > I mean are there an windows system libs that match posix-y ones?
> > Maybe I'm missing something.
> 
> Not only system libs.  Our particular use case is that
> when building nacl apps we want to link against ppapi_cpp
> (and friends) on all platforms.
> 
> I can think of many other examples of cross platform libs
> that are often distributed in binary from (SDL, libjpeg, etc).
> Having a cross platform way to say "use this lib" is surely
> a useful thing.  I guess chrome pretty much builds everything
> from source so it hasn't come up until now.

It has come up, but it tends to be resolved by

'msvs_settings': {
  'VCLinkerTool': {
    'AdditionalDependencies': [
      'z.lib',
    ],
    'AdditionalLibraryDirectories': [
      'path/to/lib/dir',
    ],
  },
},

In a related effort, there was an attempt to make library_dirs behave in a
cross-platform manner ( see https://chromiumcodereview.appspot.com/10749020/ )

> 
> TBH, I think the cleanest way to do this kind of thing would
> be to mandate that all 'libraries' are just the bare names
> and the generators know how to expand them into link args.
> e.g:
> 
> linux:  'z' -> '-lz'
> win32:  'z' -> 'z.lib'
> 
> But this change is (hopefully) much less intrusive and will
> provide a way to express cross platform libs without breaking
> any existing gyp files.

I agree, it would be nice to have a consistent, cross-platform way to do that.
One thing worth noting is that the '-l' form actually invokes "special"
behaviour in GYP, in that it doesn't force pathname relativization and doesn't
force list singleton behaviour (
http://code.google.com/p/gyp/wiki/InputFormatReference#Pathname_Relativization
). Changing to just use 'z' runs the risk of both, so it'd likely require some
careful work to get the semantics right.

[Sam Clegg, 2012-09-21 18:53:34]

On 2012/09/21 18:19:09, Ryan Sleevi wrote:
> On 2012/09/21 17:44:06, Sam Clegg wrote:
> > On 2012/09/21 05:23:47, bradn wrote:
> > > Nothing inherently bad, but what's use case?
> > > I mean are there an windows system libs that match posix-y ones?
> > > Maybe I'm missing something.
> > 
> > Not only system libs.  Our particular use case is that
> > when building nacl apps we want to link against ppapi_cpp
> > (and friends) on all platforms.
> > 
> > I can think of many other examples of cross platform libs
> > that are often distributed in binary from (SDL, libjpeg, etc).
> > Having a cross platform way to say "use this lib" is surely
> > a useful thing.  I guess chrome pretty much builds everything
> > from source so it hasn't come up until now.
> 
> It has come up, but it tends to be resolved by
> 
> 'msvs_settings': {
>   'VCLinkerTool': {
>     'AdditionalDependencies': [
>       'z.lib',
>     ],
>     'AdditionalLibraryDirectories': [
>       'path/to/lib/dir',
>     ],
>   },
> },

Yup.. this is the kind of thing I'm trying to avoid.

> 
> In a related effort, there was an attempt to make library_dirs behave in a
> cross-platform manner ( see https://chromiumcodereview.appspot.com/10749020/ )

This seems like a great idea.   I hope this is still the plan
to submit this.

> 
> > 
> > TBH, I think the cleanest way to do this kind of thing would
> > be to mandate that all 'libraries' are just the bare names
> > and the generators know how to expand them into link args.
> > e.g:
> > 
> > linux:  'z' -> '-lz'
> > win32:  'z' -> 'z.lib'
> > 
> > But this change is (hopefully) much less intrusive and will
> > provide a way to express cross platform libs without breaking
> > any existing gyp files.
> 
> I agree, it would be nice to have a consistent, cross-platform way to do that.
> One thing worth noting is that the '-l' form actually invokes "special"
> behaviour in GYP, in that it doesn't force pathname relativization and doesn't
> force list singleton behaviour (
> http://code.google.com/p/gyp/wiki/InputFormatReference#Pathname_Relativization
> ). Changing to just use 'z' runs the risk of both, so it'd likely require some
> careful work to get the semantics right.

Right, I see that would be a more involved change.