This is the mail archive of the
mailing list for the GCC project.
Re: PATCH: target/19520: protected function pointer doesn't work right
On Thu, Jan 20, 2005 at 03:59:19PM -0800, H. J. Lu wrote:
> On Thu, Jan 20, 2005 at 05:59:07PM -0500, Daniel Jacobowitz wrote:
> > On Thu, Jan 20, 2005 at 02:56:47PM -0800, H. J. Lu wrote:
> > > The issue is the function address of a protected function isn't
> > > necessarily the same as the address of the function body nor has to
> > > be in the same DSO where the function is defined. In that case, the
> > > only optimization we can do is to skip PLT when branch. This
> > > patch marks if a symbol is protected and also treats a protected
> > > function as normal. But it will skip PLT when generating the branch
> > > instruction.
> > Is there clear documentation of these very odd semantics somewhere?
> It has been that way with PLT from day 1. Basically, PLT is usually
> used to redirect the function call. Linker will resolve undefined
> function address to the PLT entry. To make sure function address
> comprison works correctly, everyone has to agree on a unique function
> address, which is the PLT entry if it will ever be used. The protected
> function makes it tricky.
That doesn't answer my question :-)
> > How about test cases?
> Is there a place I can add it? I need to build a shared library,
> link a main against it and run the main.
Binutils has a number of C tests like these already. They don't run
when cross, but they're better than nothing.