Re: gcc can not distinguish the same file or same class with the different module or library

[Andrew Haley <aph-gcc at littlepinkcloud dot COM>]

[Redirected to gcc-help@gcc.gnu.org: plese don't post questions like
this to gcc@]

summer xia writes:

 > I am porting a application from Windows into Linux. The application
 > has many modules that wrote by different persons. There are some
 > files or classes named the same name with different implement. Such
 > as the library A has the class CSky, the libary B has the class
 > CSky too. But these classes have the different implement. There is
 > no any errors when I complie the library A and library B into share
 > libraries. But when I use these libraries. I alway find that the
 > gcc link the error class(I use the gdb to debug it), such as when I
 > use the class CSky in the module B, I suppose that this class
 > should use this module internal implement( this is to say use CSky
 > implement in the library B). But it is surprised to me that CSky
 > uses the library A implement.

It's part of the language rules.  If there exists a function or an
object called foo, &foo must always return the same pointer no matter
where it is referenced from.  So, at load time your shared libraries
are scanned, and the first instance of foo is found, and that same foo
is used everywhere.

You can control what symbols are exported from a shared library by
using a version script:

       -E
       --export-dynamic

           When creating a dynamically linked executable, add all
           symbols to the dynamic symbol table.  The dynamic symbol
           table is the set of symbols which are visible from dynamic
           objects at run time.

           If you do not use this option, the dynamic symbol table
           will nor- mally contain only those symbols which are
           referenced by some dynamic object mentioned in the link.

           If you use "dlopen" to load a dynamic object which needs to
           refer back to the symbols defined by the program, rather
           than some other dynamic object, then you will probably need
           to use this option when linking the program itself.

           You can also use the version script to control what symbols
           should be added to the dynamic symbol table if the output
           format supports it.  See the description of
           --version-script in VERSION.

You can also use namespaces.  This is probably your best plan.

Andrew.