Re: problem building program: undef ref _imp__gettext

[Charles Wilson <cwilson at ece dot gatech dot edu>]

Mark Paulus wrote:

> Thanks, that worked.  But, it makes me confused.
> When I build this particular app under linux/debian,
> it does NOT have the -lintl linker flag.  And when I add
> it, the link fails.  But under cygwin, I need it.  
> 
> Can anyone out there help me reconcile the issues here.
> (So I can go back to the source and either provide a patch,
> or do whatever to get it to work in both environs).
> 
> Thanks.


Take a close look at the output from the configure script.  Many 
packages include a copy of the source for gettext (libintl) within their 
own source distribution.  If configure can't find a system library for 
it, it'll use the included source (some packages ALWAYS use the included 
source unless explicitly instructed to use the system version).

However, most autotool based packages treat the included gettext as a 
"convenience library" which means that IF using the included gettext, it 
doesn't link it via "-lintl" -- instead, it links in using a direct 
reference to the static lib: "myobj.o otherobj.o 
../gettext/intl/.libs/libintl.a moreobjs.o".

If you add ANOTHER gettext library to the same link command (e.g. 
../gettext/intl/.libs/libintl.a -lintl) you'll get duplicate symbol 
definition and the link will fail.

That's in an ideal world (linux).  On cygwin, the -lintl will find the 
dll import library (with lots of __imp__foo symbols) but the 
../gettext/intl/.libs/libintl.a is a static library and only has _foo 
symbols.  Therefore, on cygwin, you CAN include both without error -- 
because there IS no symbol duplication.  (Of course, since your object 
files are only looking for the __imp__foo symbols, the 
../get..../libintl.a is not used, even though it's specified.)  Welcome 
to Windows.

On cygwin, there are two possibilities:

  1) configure DOES find the system gettext library so it does NOT build 
the included version.  However (and here's the broken part) it neglects 
to add -lintl to the generated link line.

or

  2) configure decides to go ahead an build the included gettext.  And 
links against it using the ../gettext/intl/.libs/libintl.a method.  BUT: 
for whatever reason, the *compilation* stage of the OTHER object files 
are using the SYSTEM header files (/usr/include/gettext.h & friends) and 
NOT the included header files (../gettext/include/*).

These are different.  The SYSTEM header files assume you're going to 
link against a DLL (thus, __imp__foo).  The locally included header 
files don't know anything about DLL's -- so they only declare the _foo 
symbols. not __imp__foo). Plus, the gettext library built from the 
included sources is a static lib, so it doesn't have __imp__foo symbols, 
only _foo symbols.

the problem here is twofold:
   a) system gettext headers different from "standard" gettext headers. 
  This is unavoidable (for now) because of the whole DLL problem.
   b) the package is using the system gettext headers when compiling its 
local objects, EVEN WHEN using the local version of gettext.

Solution:
   a) workaround: Use "CFLAGS=-DGETTEXT_STATIC ./configure"  (this turns 
the system gettext headers back into the "normal" gettext version).

   b) convince your package that it ought to use its own headers when 
using its own internal libraries, and not allow system overrides.  I'm 
not sure exactly how to do this -- especially since EVERYTHING in this 
message is guesswork, because you didn't provide a whole lot of 
information.  "Problem building 'program':"  "This particular app" etc. 
  A bit light on details, wouldn't you say?  I'm not even sure your app 
is autotooled, or if it really does include its own gettext source.  I'm 
just going by the common problems with gettext that have cropped up in 
the past.

   c) fix windows/cygwin dll process so that header-file hacks are no 
longer necessary; build and release a new gettext package.  (This is my 
job; i'll get to it eventually once the binutils changes/problems are fixed)

--Chuck


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