Re: libtool uses cc to link a mixed C/C++ project and fails to find operator new

On 6/23/19 2:56 PM, Yuri wrote:
> On FreeBSD libtool can't find operator new[] because it is in C mode:
> 
> libtool: link: cc -fno-strict-aliasing -fopenmp -ftree-vectorize 
> -pthread -O2 -pipe -fno-omit-frame-pointer -fstack-protector-strong 
> -fno-strict-aliasing -fno-strict-aliasing -fstack-protector-strong -o 
> RNALfold RNALfold_cmdl.o RNALfold.o 
> ../../src/ViennaRNA/.libs/libRNA_conv.a ./.libs/libhelpers.a -lm 
> -pthread -fopenmp
> libtool: link: cc -fno-strict-aliasing -fopenmp -ftree-vectorize 
> -pthread -O2 -pipe -fno-omit-frame-pointer -fstack-protector-strong 
> -fno-strict-aliasing -fno-strict-aliasing -fstack-protector-strong -o 
> RNALalifold RNALalifold_cmdl.o RNALalifold.o 
> ../../src/ViennaRNA/.libs/libRNA_conv.a ./.libs/libhelpers.a -lm 
> -pthread -fopenmp
> ld: error: undefined symbol: operator new[](unsigned long)
>  >>> referenced by svm.cpp
>  >>>               svm.o:(Kernel::Kernel(int, svm_node* const*, 
> svm_parameter const&)) in archive ../../src/ViennaRNA/.libs/libRNA_conv.a
> 
> 
> 
> I added "LT_LANG([C++]) to configure.ac but it didn't help:
> 
> AC_PROG_LIBTOOL
> LT_INIT([pic-only, static])
> LT_LANG([C++])
> AC_SUBST(LIBTOOL_DEPS)
> 
> 
> How to switch libtool to the C++ mode?

Are you using automake?  Or just libtool and autoconf?

With automake, the info at the end of the following section in the 
manual might help:

 
https://www.gnu.org/software/automake/manual/automake.html#Libtool-Convenience-Libraries

I think the same idea applies to executable files, not just building 
libraries from a collection of convenience libraries.  So (again, with 
automake) you can trick the system into using C++ for linking by having 
a C++ source file directly in the list of files to link.  That C++ 
source file doesn't have to contain anything or even exist.  Automake 
just notes that there is a C++ file in the list of files to link and 
uses the C++ linker.

jwe

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