More questions about _GLOBAL

[Anthony Green]

On Tue, 2002-01-29 at 09:54, Adam Megacz wrote:
> 1. Since we don't know which _GLOBAL symbols should be invoked on
>    startup until the link phase, does this mean that the linker
>    actually generates the code for __main()?

I think the linker puts together data which is used by __main.  BTW, the
static initializer you're seeing (which calls the register class
function) isn't used on ELF systems.  We use a special section called
.jcr which contains a list of pointers to classes which need
registration.  Try compiling to a .s and looking for references to the
_GLOBAL* symbol.

> 2. How does the linker know which symbols should be invoked on startup
>    and which shouldn't? Is "_GLOBAL" a "magic prefix"?

I can only speak for ELF systems, in which case a list of pointers to
these functions is placed in a special section, and the linker pulls
them together into one list which is traversed at program startup.

> 3. Is there any way for me to remove one of these _GLOBAL__ sections
>    from a .o after compilation, without causing __main() to jump to an
>    undefined/invalid address? If I simply remove the section (strip
>    -R), __main() seems to call some other randomly-chosen section
>    instead, which, of course, causes my program to barf all over the
>    place.

Hmm... I'm not sure I understand what you're asking.  You need these
_GLOBAL__ functions to implement static initializers.

AG