Re: [Openexr-devel] "Half" support in C?

[Bob Friesenhahn]

On Wed, 2 Mar 2005, Drew Hess wrote:

> Bob Friesenhahn <address@hidden> writes:
>
> > On Wed, 2 Mar 2005, Derek Gerstmann wrote:
> > > Currently, we've been using the Half class from OpenEXR and compiling
> > > our C code as C++, which has limited the adoption of Half support
> > > to simple standalone modules that are linked dynamically.
> >
> > Unfortunately, there are people who have a good C compiler but no
> > C++. This is not uncommon for people who depend on vendor (e.g. IBM
> > AIX) compilers which are expensive.
>
> Do you have an example of such a platform where gcc is either not
> available, or isn't ABI-compliant such that code compiled with it
> can't interoperate with the commercial compiler?

GCC supports most platforms.  The code it generates may not be as 
efficient as some vendor compilers.

The typical situation is that it is easy for GCC code to link with 
OS/vendor libraries (the normal case).  It is problematic for vendor 
compilers to link with libraries build with GCC (even C libraries) 
because code built with GCC expects certain support functions (e.g. 
_eprintf) to exist.  Adding libgcc to the mix may cause other problems 
(e.g. duplicate symbols).

Due to C++ initialization and symbol dependency issues, it may be very 
difficult for code from a vendor compiler to link properly with GCC 
created C++ libraries.  It will help to link the C code using g++.

The upshot is that depending on GNU C++ to satisfy the requirement is 
not satisfactory unless GNU C/C++ is used for the whole build.  Even 
then, introducing a C++ component into an otherwise C application 
requires that the C application be linked using the C++ compiler.

Bob
======================================
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/