[GRASS-dev] Re: r.viewshed ready for testing

[Glynn Clements]

Paul Kelly wrote:

> > So I got the trunk version of GRASS, and compiled it, but iostream and
> > r.terraflow gave me errors.  As the instructions say, I tackled the iostream
> > error first, and I can't figure out what's wrong with it.   Here is what I
> > get if I call make in grass_trunk/lib/iostream
> >
> > cc -dynamiclib -compatibility_version 7.0 -current_version 7.0 -install_name
>    ^^
> GRASS is trying to use the C compiler to create the shared library - this 
> worked on Linux so I didn't notice it but obviously that must have been 
> just luck and it seems not to work on OS X. This clearly is something I 
> need to look at and try to fix - none of the other libraries contain C++ 
> code so this hasn't come up before.

Another issue with making IOStream a dynamic library is that
Shlib.make only adds $(SHLIB_CFLAGS) to CFLAGS, not to CXXFLAGS.

On Linux, this causes the code to be compiled without -fPIC, resulting
in:

	warning: creating a DT_TEXTREL in object.

Normally, this is just an efficiency issue (the library won't actually
be shared; each process will have a separate copy), but it won't work
on systems running SELinux (to perform relocation, the code segment
has to be modified, and SELinux won't let it regain execute permission
after it has been modified).

Also, the effect will vary between platforms. The Darwin case in
SC_CONFIG_FLAGS has:

	    SHLIB_CFLAGS="-fno-common"

ISTR that this may be a necessity for building dynamic libraries on
that platform.

I'll commit a fix for this as soon as I have tested it.

-- 
Glynn Clements <glynn at gclements.plus.com>