Re: RFA symtab: Fix for PR c++/1267 ("next" and shared libraries)

[Adam Fedor <fedor@doc.com>]

Daniel Jacobowitz wrote:
> This patch fixes c++/1267, a bug where stepping over a function call that
> went through the PLT (as happens when a -fPIC function makes a call to a
> globally visible symbol) would lose control of the inferior.  I'll spare you
> the complete debugging session, as it really doesn't make much sense.  But
> here's the root of the problem:
> 
> When we called frame_pc_unwind on the sentinel frame, we got an address in
> the PLT.  But when we called frame_func_unwind, we got "_init", in ".init",
> which is generally located right before the PLT.  Then, we'd run the
> new-and-improved prologue unwinder on _init, and get some completely bogus
> information, since things weren't actually saved on the stack where it
> thought they were.  This led to the unwound stack pointer being wrong for
> the step_resume breakpoint, so when we hit the step_resume breakpoint we
> kept going.
> 
> I fixed this by changing lookup_minimal_symbol_pc_section to be paranoid
> about returning a minsym in the same section as the PC.  Technically, at
> least on ELF targets, that doesn't _have_ to be true.  I've never
> encountered an exception or a good reason for one, though.  Does anyone see
> any pitfalls for this change?  Symtab maintainers, is this patch OK?
> 
> I believe this patch should also fix shlibs/1237, and may also fix
> shlibs/1280.  Adam, could you check those?
> 

Yes this fixes both cases (shlibs/1237 and shlibs/1280) for me. Thanks!