Specify how undefined weak symbol should be resolved in executable

[Michael Matz]

Hi,

On Tue, 23 Feb 2016, H.J. Lu wrote:

> >> Not only we need to change defined weak symbol behavior, we also need 
> >> to change undefined non-weak symbol behavior when taking its address.
> >
> > Why?  An undefined non-weak symbol reference leads to a linker error, 
> > done.  Why change that?
> 
> Make it "external non-weak symbol", which is a symbol defined in a 
> shared object.

What would you like to change in behaviour for them (and why must it be 
done at the same time as changing something for weak symbols)?  A 
reference to the address of such a function symbol from an executable 
resolves to the plt slot currently (which in turn is exported, so that 
address references from other modules resolve to the same).  A reference 
to a non-function symbol is loaded from the got.  In all cases must this 
symbol be defined somewhere (otherwise linker error), so I don't see what 
we need to change, nor why that would force DT_TEXTREL (or the compiler to 
emit PIC like code).


Ciao,
Michael.