Re: Framework support for darwin

[Devang Patel <dpatel at apple dot com>]

On Monday, August 11, 2003, at 11:08 PM, Geoff Keating wrote:

> > > Ah, but we don't want the file entered into the hash table.  Since 
> > > the
> > > lookup is context dependent, an entry in a hash table would defeat 
> > > the
> > > next context dependent lookup, making it context independent, which, 
> > > is
> > > wrong.
> >
> > Yuk!  This is nasty.  Including the same thing and getting something
> > different is ... counterintuitive.
>
> I agree.  We don't need or want that functionality.

I think, Mike is talking about sub-frameworks here. In that case 
requirement
is unavoidable. However implementation is a different issue. I'll try to
summarize requirements for framework support.

Mac OS X uses frameworks to package related dynamic library, headers,
precomps (and symbol repositories?) together. Mac OS X GCC and cctools 
(as,
ld, libtool etc..) support this mechanism.

Directory layout:

Frameworks use very specific directory layout. Tools rely on this fixed
directory layout.
(1) Framework is enclosed in a directory whose name always ends with 
".framework".
    For example, Carbon.framework
(2) In .framework directory headers are always stored in "Headers" or
    "PrivateHeaders" sudirectories.
(3) If framework encloses other sub-frameworks than it is an umbrella 
framework.
    All sub-frameworks also uses standard framework directory layout 
(as per (1)
    and (2)) and they are located in "Frameworks" directory inside 
umbrella
    .framework directory.
(4) Sub-frameworks are not visible outside their parent framework.

For example,

/somewhere/A.framework/Headers/A.h
/somewhere/A.framework/Headers/A1.h
/somewhere/A.framework/PrivateHeaders/A_fun1.h
/somewhere/A.framework/PrivateHeaders/A_fun2.h
/somewhere/A.framework/PrivateHeaders/A_fun3.h
/somewhere/A.framework/Frameworks/B.framework/Headers/B.h
/somewhere/A.framework/Frameworks/B.framework/PrivateHeaders/B_priv.h
/somewhere/A.framework/Frameworks/C.framework/Headers/C.h
/somewhere/A.framework/Frameworks/C.framework/PrivateHeaders/C_priv.h

In this example, A is an Umbrella Framework. Sub-frameworks, e.g. B and 
C, are not
visible outside parent framework A (when user supplies -F /somewhere). 
Which means
A.h can include headers from B and C frameworks. Users can only include 
headers from
framework A in their source. They can not directly include B.h in their 
source.

Command Line options:

(1) -F <path>

GCC uses <path> to find main framework directory. -F is like -I. GCC 
supplies user
provided -F to link editor also. "/System/Library/Framework" is default 
framework
search path.

(2) -framework <name>

GCC driver passes this -framework and its option to link editor. Link 
editor uses
it to find library hidden inside .framework directory structure.

(3) -iframework
Equivalent of -iprefix.

-
Devang