Re: [RFC/RFA] find_pc_sect_psymtab(): symbol table not always complete

[Elena Zannoni <ezannoni at redhat dot com>]

Joel Brobecker writes:


 Joel, I committed an updated version of your patch. By updated I mean
 with new/more comments. Now let's keep an eye on any apparently
 unrelated breakage :-)

elena

2004-02-19  Joel Brobecker  <brobecker@gnat.com>

	Committed by Elena Zannoni  <ezannoni@redhat.com>
	* symtab.c (find_pc_sect_psymtab): Return the psymtab that
	contains a symbol wich is the best, non-exact match for the given
	pc.  Update comments.


Index: symtab.c
===================================================================
RCS file: /cvs/src/src/gdb/symtab.c,v
retrieving revision 1.127
diff -u -p -r1.127 symtab.c
--- symtab.c    17 Feb 2004 15:21:22 -0000      1.127
+++ symtab.c    19 Feb 2004 17:13:11 -0000
@@ -672,8 +672,10 @@ init_sal (struct symtab_and_line *sal)
 
  
  
-/* Find which partial symtab on contains PC and SECTION.  Return 0 if none.  */-
+/* Find which partial symtab contains PC and SECTION.  Return 0 if
+   none.  We return the psymtab that contains a symbol whose address
+   exactly matches PC, or, if we cannot find an exact match, the
+   psymtab that contains a symbol whose address is closest to PC.  */
 struct partial_symtab *
 find_pc_sect_psymtab (CORE_ADDR pc, asection *section)
 {
@@ -698,6 +700,8 @@ find_pc_sect_psymtab (CORE_ADDR pc, asec
     if (pc >= pst->textlow && pc < pst->texthigh)
       {
        struct partial_symtab *tpst;
+       struct partial_symtab *best_pst = pst;
+       struct partial_symbol *best_psym = NULL;
  
        /* An objfile that has its functions reordered might have
           many partial symbol tables containing the PC, but
@@ -710,6 +714,13 @@ find_pc_sect_psymtab (CORE_ADDR pc, asec
        if (msymbol == NULL)
          return (pst);
  
+       /* The code range of partial symtabs sometimes overlap, so, in
+          the loop below, we need to check all partial symtabs and
+          find the one that fits better for the given PC address. We
+          select the partial symtab that contains a symbol whose
+          address is closest to the PC address.  By closest we mean
+          that find_pc_sect_symbol returns the symbol with address
+          that is closest and still less than the given PC.  */
        for (tpst = pst; tpst != NULL; tpst = tpst->next)
          {
            if (pc >= tpst->textlow && pc < tpst->texthigh)
@@ -721,9 +732,33 @@ find_pc_sect_psymtab (CORE_ADDR pc, asec
                    && SYMBOL_VALUE_ADDRESS (p)
                    == SYMBOL_VALUE_ADDRESS (msymbol))
                  return (tpst);
+               if (p != NULL)
+                 {
+                   /* We found a symbol in this partial symtab which
+                      matches (or is closest to) PC, check whether it
+                      is closer than our current BEST_PSYM.  Since
+                      this symbol address is necessarily lower or
+                      equal to PC, the symbol closer to PC is the
+                      symbol which address is the highest.  */
+                   /* This way we return the psymtab which contains
+                      such best match symbol. This can help in cases
+                      where the symbol information/debuginfo is not
+                      complete, like for instance on IRIX6 with gcc,
+                      where no debug info is emitted for
+                      statics. (See also the nodebug.exp
+                      testcase.)  */
+                   if (best_psym == NULL
+                       || SYMBOL_VALUE_ADDRESS (p)
+                       > SYMBOL_VALUE_ADDRESS (best_psym))
+                     {
+                       best_psym = p;
+                       best_pst = tpst;
+                     }
+                 }
+
              }
          }
-       return (pst);
+       return (best_pst);
       }
   }
   return (NULL);