Re: [RFC]: Disallow ObjC search when resetting breakpoint.

[Elena Zannoni <ezannoni at redhat dot com>]

Adam Fedor writes:
 > This patch fixes PR objc/1238, where you get frustrating behavior if
 > there is an ObjC method with the same name as a function:
 > 
 > (gdb) break init
 > [0] cancel
 > [1] all
 > [2] -[MyObject init] at gdb-objc-test.m:50
 > [3] -[NewObject init] at gdb-objc-test.m:18
 > [4] init at gdb-objc-test.m:62
 > > 4
 > Breakpoint 1 at 0x10001a40: file gdb-objc-test.m, line 62.
 > (gdb) run
 > Starting program:
 > /home/users/fedor/src/gstep/Tester/shared_debug_obj/gdb-objc-test 
 > [0] cancel
 > [1] all
 > [2] -[MyObject init] at gdb-objc-test.m:50
 > [3] -[NewObject init] at gdb-objc-test.m:18
 > [4] init at gdb-objc-test.m:62
 > > 0
 > Error in re-setting breakpoint 1:
 > canceled
 > [Thread debugging using libthread_db enabled]
 > [New Thread 16384 (LWP 2249)]
 > [0] cancel
 > [1] all
 > [2] -[MyObject init] at gdb-objc-test.m:50
 > [3] -[NewObject init] at gdb-objc-test.m:18
 > [4] init at gdb-objc-test.m:62
 > > 
 > [... on and on ad infinitum ...]
 > 
 > What happens is that every time you try to reset a breakpoint,
 > decode_line_1 gets called and we search through all the ObjC selectors
 > for a match to the breakpoint and there are always multiple matches to
 > "init".
 > 
 > I don't particularly like the solution (It's the way Apple does it,
 > although it might be for more reasons than this, e.g. there's no reason
 > to go through the ObjC selector search when resetting a breakpoint
 > anyway). I can't think of any other way to do it though, unless perhaps
 > there is some way to canonicalize the symbol name for the breakpoint -
 > so it's something like "gdb-objc-test.m:init", and not just "init" -
 > then you won't get multiple matches.
 > 
 > Any comments?
 > 
 > 
 > 2003-10-16  Adam Fedor  <fedor@gnu.org>
 > 
 > 	* gdb/linespec.c (decode_line_1): Search for ObjC selectors
 > 	only if allow_objc_selectors_flag.
 > 	* gdb/breakpoint.c (breakpoint_re_set_one): Don't allow search
 > 	for ObjC selectors when resetting a breakpoint.
 > 
 > Index: gdb/breakpoint.c
 > ===================================================================
 > RCS file: /cvs/src/src/gdb/breakpoint.c,v
 > retrieving revision 1.132
 > diff -u -p -r1.132 breakpoint.c
 > --- gdb/breakpoint.c	13 Oct 2003 23:53:20 -0000	1.132
 > +++ gdb/breakpoint.c	17 Oct 2003 03:41:32 -0000
 > @@ -52,6 +52,8 @@
 >  
 >  #include "gdb-events.h"
 >  
 > +extern int allow_objc_selectors_flag;
 > +
 >  /* Prototypes for local functions. */
 >  
 >  static void until_break_command_continuation (struct continuation_arg *arg);
 > @@ -6854,7 +6856,9 @@ breakpoint_re_set_one (void *bint)
 >        set_language (b->language);
 >        input_radix = b->input_radix;
 >        s = b->addr_string;
 > +      allow_objc_selectors_flag = 0;
 >        sals = decode_line_1 (&s, 1, (struct symtab *) NULL, 0, (char ***) NULL);
 > +      allow_objc_selectors_flag = 1;
 >        for (i = 0; i < sals.nelts; i++)
 >  	{
 >  	  resolve_sal_pc (&sals.sals[i]);
 > Index: gdb/linespec.c
 > ===================================================================
 > RCS file: /cvs/src/src/gdb/linespec.c,v
 > retrieving revision 1.51
 > diff -u -p -r1.51 linespec.c
 > --- gdb/linespec.c	2 Aug 2003 03:59:40 -0000	1.51
 > +++ gdb/linespec.c	17 Oct 2003 03:41:34 -0000
 > @@ -36,6 +36,8 @@
 >  #include "objc-lang.h"
 >  #include "linespec.h"
 >  
 > +int allow_objc_selectors_flag = 1;
 > +
 >  /* We share this one with symtab.c, but it is not exported widely. */
 >  
 >  extern char *operator_chars (char *, char **);
 > @@ -698,6 +700,7 @@ decode_line_1 (char **argptr, int funfir
 >  
 >    /* Check if the symbol could be an Objective-C selector.  */
 >  
 > +  if (allow_objc_selectors_flag)
 >    {
 >      struct symtabs_and_lines values;
 >      values = decode_objc (argptr, funfirstline, NULL,


Hmm, not sure about this. Maybe it is the code that follows your new
'if' in decode_line_1 that should be changed.  Definitely saving more
info in the breakpoints would be helpful.

Question: how does this work for overloaded functions in c++?
decode_line_1 calls decode_compounds, which calls find_method, which
calls decode_line_2, which asks the user. I would think a similar
problem arises there. If not, then can we make objc do the same thing
that c++ does?

elena