Date: Wed, 23 Jul 2014 14:10:36 +0200 From: Tijl Coosemans <tijl@FreeBSD.org> To: Baptiste Daroussin <bapt@FreeBSD.org> Cc: svn-ports-head@freebsd.org, kwm@FreeBSD.org, svn-ports-all@freebsd.org, marino@freebsd.org, ports-committers@freebsd.org Subject: Re: svn commit: r362304 - head/x11-toolkits/pango Message-ID: <20140723141036.27896d0a@kalimero.tijl.coosemans.org> In-Reply-To: <20140721135342.GC26699@ivaldir.etoilebsd.net> References: <53CBF2D7.4070005@marino.st> <20140721013342.6c17ecdc@kalimero.tijl.coosemans.org> <53CCABFA.7090202@marino.st> <20140721121214.1d1f3ef5@kalimero.tijl.coosemans.org> <53CCF19B.3060906@marino.st> <20140721132621.64ef394c@kalimero.tijl.coosemans.org> <53CD047B.7080104@marino.st> <20140721144356.72c4e5c2@kalimero.tijl.coosemans.org> <53CD0F04.4040709@marino.st> <20140721153657.17c64594@kalimero.tijl.coosemans.org> <20140721135342.GC26699@ivaldir.etoilebsd.net>
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On Mon, 21 Jul 2014 15:53:42 +0200 Baptiste Daroussin wrote:
> On Mon, Jul 21, 2014 at 03:36:57PM +0200, Tijl Coosemans wrote:
>> On Mon, 21 Jul 2014 15:00:52 +0200 John Marino wrote:
>>> On 7/21/2014 14:43, Tijl Coosemans wrote:
>>>> On Mon, 21 Jul 2014 14:15:55 +0200 John Marino wrote:
>>>>> On 7/21/2014 13:26, Tijl Coosemans wrote:
>>>>>> On Mon, 21 Jul 2014 12:55:23 +0200 John Marino wrote:
>>>>>>> Everything that uses a pango function that has a libm symbol must a=
lso
>>>>>>> link with libm.
>>>>>>
>>>>>> This is a completely false statement. If X links to Y and Y uses Z
>>>>>> symbols, you do not have to link X with Z. Y links with Z and that =
is
>>>>>> enough. Otherwise X would have to link with its entire dependency
>>>>>> tree.
>>>>>
>>>>> If the linker doesn't follow Y's link to Z, how is it supposed to
>>>>> resolve Z references?
>>>>=20
>>>> If X doesn't contain Z references the linker doesn't have to resolve
>>>> Z references.
>>>>=20
>>>> If X does contain Z references then explicit linking requires that you
>>>> explicitly link X with -lZ and that you cannot rely on -lY to imply -l=
Z.
>>>=20
>>> This seems to be the heart of our disagreement.
>>> I am saying X can pull in a function of Y that contains a symbol of Z.
>>> In that case, there's no reference of Z in X, but when linking X it
>>> still needs -lZ.
>>=20
>> Let's work out an example:
>>=20
>> -- X.c --
>> void funcY( void );
>> int main( void ) {
>> funcY();
>> return( 0 );
>> }
>> ---------
>>=20
>> -- Y.c --
>> void funcZ( void );
>> void funcY( void ) {
>> funcZ();
>> }
>> ---------
>>=20
>> -- Z.c --
>> #include <stdio.h>
>> void funcZ( void ) {
>> ( void ) puts( "Hello world" );
>> }
>> ---------
>>=20
>> Create libZ.so:
>> % cc -shared -o libZ.so Z.c
>>=20
>> Create libY.so linking it with libZ:
>> % cc -shared -o libY.so Y.c -Wl,-rpath,. -L. -lZ
>>=20
>> Create X linking it with libY, but not libZ:
>> % cc -o X X.c -Wl,-rpath,. -L. -lY
>>=20
>> Run ./X:
>> % ./X
>> Hello world
>>=20
>>=20
>> Now, what do you get?
>=20
> print/libharu is a good example that shows the problem. for which anyway
> explicit linking is a wrong idea :)
>=20
> so if one uses binutils from ports instead of binutils from base one of t=
he demo
> (text_demo2.c) will fail to link (text_demo2.c explicitly uses a libm fun=
ction)
> while with base binutils (ld) it will build without problems meaning that
> somehow we are still leaking implicit dependencies.
>=20
> So the thing is we do not yet see problems found by dports because our li=
nker
> still leaks implicit libraries... :(
>=20
> Still adding explicit linking to all .pc files is not the right solution.
I've submitted a PR to track this:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D192062
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