Re: -no-undefined vs gcc 4.6.0

[Vincent Torri]

On Sat, 19 Mar 2011, LRN wrote:


On 19.03.2011 0:17, Vincent Torri wrote:



On Sat, 19 Mar 2011, LRN wrote:


On 18.03.2011 23:51, Vincent Torri wrote:



On Fri, 18 Mar 2011, LRN wrote:


Since gcc 4.6.0 it is no longer possible to use LDFLAGS=-no-undefined
gcc now says something like this:
gcc.exe: error: unrecognized option '-no-undefined'
Before 4.6.0 it was possible to do that, and gcc said only this:
gcc.exe: unrecognized option '-no-undefined'
That is, unrecognized option was not considered a show-stopper, and 
everything worked just fine - the option, being part of LDFLAGS, 
eventually reached libtool, and libtool were taking the clue to disallow 
undefined symbols. Not anymore. Now i have to pass 
LDFLAGS=-Wl,-no-undefined. Which is ok from gcc' point of view, but 
libtool is unable to recognize this argument in such form and simply 
refuses to build shared libraries outright.
Not sure if it's a bug or a feature, and how to work through that 
without making groundbreaking changes in software packages that use 
libtool.


I think that you have to pass -no-undefined to the ***_LDFLAGS variable 
of your library:


lib_LTLIBRARIES = libproject.la
libproject_la_LDFLAGS = -no-undefined

or, globally:

AM_LDFLAGS = -no-undefined

it has always worked for me, without gcc warning.


It's not my library. I'm compiling mpc-0.8.2


ok. Anyway you have to pass -Wl,-no-undefined. It's an option for the 
linker [1], not for gcc [2]


Vincent Torri

[1] http://unixhelp.ed.ac.uk/CGI/man-cgi?ld
[2] http://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#Link-Options
I *know* that it's a linker option. And i know that i have to pass it with 
-Wl because of that. What i do not know is how to make libtool see it when it 
is passed like that.


Finally got it to work with `make libmpc_la_LDFLAGS=-version-info 2:0:0 
-no-undefined', because mpc does not use AM_LDFLAGS in the link command that


i'm wondering if you ever read my first answer...

Vincent


is used to build libmpc (mpc devs are probably the ones to blame, but right 
now i just want to make it work). Although i've found no way to pass such an 
option with spaces to `make' from a variable expansion (i.e. `make $opts'), 
so i've had to hard-code it into make invocation instead.


I expect to find a lot of libtool-using projects that will require such hacks 
or workarounds, because `unrecognized option  '-no-undefined'' is very 
common.


___
http://lists.gnu.org/mailman/listinfo/libtool




___
http://lists.gnu.org/mailman/listinfo/libtool

Re: -no-undefined vs gcc 4.6.0

[Charles Wilson]

On 3/19/2011 6:25 AM, LRN wrote:

 I expect to find a lot of libtool-using projects that will require such
 hacks or workarounds, because `unrecognized option  '-no-undefined'' is
 very common.

Ah, but actually -no-undefined should be added by the upstream
maintainers, in Makefile.am, to libfoo_la_LDFLAGS.  It is a
*description* of the library -- which is true regardless of the host
platform the library is being built for.

It is a claim by the library designer that: This library, when linked,
will not reference any symbols, unless they are defined either in its
own source objects or in other explicitly listed dependencies

In order to build a library on win32/cygwin, libtool requires that the
library designer assure it of this fact.

So, either a library DOES or DOES NOT satisfy the claim: if it doesn't,
then it can't be built on windows without massive surgery. If it does,
then it does no harm to tell ALL platforms that it does so -- thus,
upstream should add -no-undefined to their Makefile.am/libfoo_la_LDFLAGS.

This declaration is usually NOT passed via an explicit variable
statement on the make or configure command line.

--
Chuck

___
http://lists.gnu.org/mailman/listinfo/libtool