Re: Octave & Fortran continued

[Benjamin Lindner]

> Linking against shared libgcc should be doable by simply doing
> ./configure ... LDFLAGS="-shared-libgcc"...
> at least for libtool-based build. No source change required. 

Theoretically yes, in reality no.
new versions of libtool (in my case version 2.2.6 as used in fftw3-3.2) 
fail to honor this flag.
The problem with libtool is that it tries to think too much for itself, 
(which is practically never a good thing). the configure script creates 
a command line, libtool now rescans the command line, interprets it and 
then creates a new command line for the compiler/linker to be called 
eventually. And in rescanning, the flag "-shared-libgcc" is not added to 
linker flags, as a LDFLAGS=-shared-libgcc would suggest.
It works for older versions, though.
So some patching is required here.

> What about shared libstdc++? What is needed to link against it?

1) CXXFLAGS="-D_DLL" (declares the C++ standard library as __dllimport 
in the headers) and
2) the addition of "-lstdc++_s" as the *last* library on the command 
line, more concise, *after* any other library that references libstd++ 
(this is due to GNU ld's method-of-work). But this cannot be done by a 
simple LIBS="-lstdc++_s", since
a) it's a g++ (not a gcc) libray. gcc does not require it, and it might 
no be found by gcc's lib search paths, and - more important -
b) you can practically never guarantee that the configure stage does not 
add libraries after the ones specified on the command line in which case 
 you might run into problems with undefined references.

So the way I took is adding a new configure variable CXXLIBS (in the 
style of LIBS and FLIBS) which I add at the appropriate places in the 
various makefiles, and call the configure script as
./configure CXXFLAGS="-D_DLL" CXXLIBS="-lstd++_s" LDFLAGS="-shared-libgcc"

Using TDM's gcc-4.3.0-2 this procedure works well.

benjamin