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Re: Automake passing CFLAGS or CXXFLAGS when linking


From: Grégory Pakosz
Subject: Re: Automake passing CFLAGS or CXXFLAGS when linking
Date: Tue, 19 Jul 2016 15:22:43 +0200

For those landing on this thread, here is the commit that introduces
the behavior

commit dbf75997a9c86dcf92e94aeba6d1e5ffa1b0799c
Author: Tom Tromey <address@hidden>
Date:   Thu May 1 01:18:21 1997 +0000

    some patches from ian
    put var index into final index
    put CFLAGS into LINK

Gregory

On Sat, Jul 2, 2016 at 9:05 AM, Grégory Pakosz <address@hidden> wrote:
> Thanks for the reply Bob.
>
> Well I indeed copy pasted from a Libtoolized project (by mistake) but
> first I noticed CFLAGS and CXXFLAGS where used when linking in a plain
> Automake project:
>
> LINK = $(CCLD) $(AM_CFLAGS) $(CFLAGS) $(AM_LDFLAGS) $(LDFLAGS) -o $@
>
> CXXLINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) $(AM_LDFLAGS) $(LDFLAGS) -o $@
>
> Also, as far as I can tell, Libtool filters flag only when linking
> shared libraries.
>
> Gregory
>
> On Fri, Jul 1, 2016 at 3:33 PM, Bob Friesenhahn
> <address@hidden> wrote:
>> On Tue, 28 Jun 2016, Grégory Pakosz wrote:
>>
>>> Hello,
>>>
>>> What's the rationale behind Automake passing CFLAGS or CXXFLAGS when
>>> linking?
>>>
>>> LINK = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
>>>  $(LIBTOOLFLAGS) --mode=link $(CCLD) $(AM_CFLAGS) $(CFLAGS) \
>>>  $(AM_LDFLAGS) $(LDFLAGS) -o $@
>>
>>
>> Notice that these lines all start with $(LIBTOOL).  Libtool will normally
>> discard flags not needed for linking.  It is common for libtool to link
>> using the C compiler when possible and so the C compiler can also
>> use/discard options as needed.
>>
>> Bob
>> --
>> Bob Friesenhahn
>> address@hidden, http://www.simplesystems.org/users/bfriesen/
>> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/



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