RE: library search test fails, please help

[aaragon]

Yes, I figured that the weird looking symbol is compiler specific. Then it
also means that I won't be able to use the c++filt command with anything
other than symbols created by the GNU C++ compiler right? I mean, if I
compile the code with the Intel compiler, most likely this function won't
work.

The fact that there is no macro for C++ functions indicate that either a)
people do not use autotools when working with with C++ programs; b) they do,
but they are very good writing m4 macros for testing C++ code, macros that
are not published anywhere in the web; c) the developers of autotools do not
write C++ code and they don't care about implementing a macro to test for
them. As for me, I'm just a user, and it would be very difficult to
implement a macro to do these tests. Even if I come up with a test, it might
be very nasty.

aa


John Calcote-2 wrote:
> 
> Aragon,
> 
> As you've already figured out, AC_CHECK_LIB was designed for C linkage.
> That
> means that you'd need to name your function exactly as it is exported by
> your library - eg., ZN8cpputils4flipEd (minus the leading underscore
> character) - in order to trick the macro into finding it. This is a hack,
> but it's better than redefining your function with C linkage in your
> library.
> 
> Autoconf does appear to provide a framework for different languages. But a
> quick examination of /usr/share/autoconf/autoconf/c.m4 shows that the C++
> version of AC_LANG_CALL (used by AC_CHECK_LIB) is just a copy of the C
> version of that macro. Other languages can't get away with such a cavalier
> attitude (as they're not as close to the C language). But it would be nice
> if someone would rewrite AC_LANG_CALL(C++) to actually handle C++ linkage.
> 
> In fairness, this may cause more problems than it would solve, because
> while
> some might want to look for a function exported with C++ linkage, MOST C++
> libraries provide at least ONE global function that is exported with C
> linkage. The idea with AC_CHECK_LIB isn't to find the function you want to
> call here, but rather to simply be pretty sure that the library you've
> found
> is the one you're interested in. If you want to find a specific function,
> then try AC_SEARCH_LIBS. But be careful, you'll find some of the same
> issues
> with that macro, as well as some issues of its own.
> 
> Kind regards,
> John
> 
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On Behalf Of
> aaragon
> Sent: Sunday, February 22, 2009 8:31 PM
> To: address@hidden
> Subject: Re: library search test fails, please help
> 
> 
> cpputils is a C++ library I wrote. The result from that command is 
> 
> address@hidden:~/Lib/lib$ nm -g libcpputils.so | grep flip
> 00003c20 T _ZN8cpputils4flipEd
> 
> and if I filter that using c++filt:
> 
> address@hidden:~/Lib/lib$ nm -g libcpputils.so | grep flip |
> c++filt
> 00003c20 T cpputils::flip(double)
> 
> Is there a way to make this macro work with C++ functions??? for the time
> being, I thought that it might be a very good idea to create a function
> with
> C linkage, so for example in my library I wrote:
> 
> extern "C" {
>     int cpputils_autotools() {
>         return 0;
>     }
> }
> 
> so I can use that function in the test for autotools. This I guess is
> something that should be done automatically by autotools when creating C++
> libraries, so that people don't break their head agains the wall trying to
> find out why the macros to test for libraries don't work.
> 
> aa
> 
> 
> 
> Peter O'Gorman wrote:
>> 
>> aaragon wrote:
>>> Hello,
>>> 
>>> I found working with autoconf sometimes very frustrating. This is an
>>> example. I want to check for a particular static library that I created.
>>> Thus, I put the following in the configure.ac file
>> 
>>> configure:15785: g++-mp-4.3 -g -O3 -o conftest -g -O2
>>> -I/Users/aaragon/Lib/include -L/Users/aaragon/Lib/lib conftest.cpp
>>> -lcpputils   >&5
>>> Undefined symbols:
>>>   "_flip", referenced from:
>> 
>> 
>> I'm guessing that the cpputils library does not define "_flip". Does nm
>> -g libcpputils.a | grep _flip show it with a capital letter?
>> 
>> Peter
>> -- 
>> Peter O'Gorman
>> http://pogma.com
>> 
>> 
>> _______________________________________________
>> Autoconf mailing list
>> address@hidden
>> http://lists.gnu.org/mailman/listinfo/autoconf
>> 
>> 
> 
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