Re: [rfa] delete lookup_symbol_aux_minsyms

[Elena Zannoni <ezannoni@redhat.com>]

David Carlton writes:
 > On Mon, 24 Feb 2003 13:21:55 -0500, Elena Zannoni <ezannoni@redhat.com> said:
 > 
 > > Actually, I did some gcov on that function last night, running make check,
 > > here is what I got.
 > 
 > > About deleting the function. I think I would prefer if we delete the
 > > 'else' part first. Then comment out the function.
 > 
 > > But I am still not convinced that we should delete it yet.
 > 
 > I'm not an expert on 'gcov': does the data you presented mean that, in
 > some situation where lookup_symbol_aux_minsyms was called 1442 times,
 > the else block was called 2 times?  So you're worried about those 2
 > times, that they produced correct information that wouldn't have been
 > reached if we deleted the 'else' clause?
 > 

Yes, each number is the number of times that the line is executed.  I
am not particularly worried about the 'else' clause. I agree that it's
dumb. I think it's ok to delete that.
The numbers were more like 'food for thoughts'.

elena


 > If so, here's the situation with the 'else' clause.  That clause calls
 > lookup_symbol_aux with a mangled name as the 'name' argument.  But the
 > 'name' argument to lookup_symbol_aux should never be mangled: calls to
 > lookup_symbol_aux always ultimately boil down to a call to
 > lookup_block_symbol.  And lookup_block_symbol needs a demangled name
 > as its 'name' argument, not a mangled name: blocks are hashed by their
 > demangled names, so passing in a mangled name is likely to result in
 > searching in the wrong bucket.  There might be times when
 > lookup_block_symbol returns the correct value when you pass in a
 > mangled name as the 'name' argument, but, if so, that's purely
 > accidental; and, in those situations, the same symbol would have been
 > found in the psymtab search that follows the call to
 > lookup_symbol_aux_minsyms.
 > 
 > Here's the current control flow, more or less:
 > 
 > * Search symtabs.
 > 
 > * Search minsyms.
 > 
 > ** Maybe then call lookup_symbol_aux with a demangled name as the
 >    'name' argument, in which case we:
 > 
 > ** Search symtabs again, with mangled name.
 > 
 > ** Search minsyms again, with mangled name.
 > 
 > ** Search psymtabs, with mangled name.
 > 
 > * Search psymtabs (with demangled name).
 > 
 > 
 > The 'else' clause is the stuff that I've labeled with two asterisks.
 > I don't see how the 'search symtabs again' or 'search minsyms again'
 > parts could ever return anything useful.  And the 'search psymtabs,
 > with mangled name', might accidentally sometimes find the variable
 > we're looking for; if so, however, the outer 'search psymtabs (with
 > demangled name)' would have found it as well, and would do so much
 > more reliably.
 > 
 > David Carlton
 > carlton@math.stanford.edu