Re: [RFA] Nullified garbage-collected global variables

Jerome Guitton
2010-07-21T13:30:33Z

Tom Tromey (tromey@redhat.com):

> >>>>> "Jerome" == Jerome Guitton <guitton@adacore.com> writes:
>
> Jerome> * dwarf2read.c (add_partial_symbol): Do not add a global variable if
> Jerome> its adress is null. Add comment to explain why.
> Jerome> (new_symbol): Ditto.
>
> This is ok. Thanks.

Thank you. I was actually polishing my tests when I realized that I was
missing a case (partial symbols for static variables). I've modified
my patch to handle it; it actually makes it cleaner, I think.

Unless you object, I will commit this new version.

gdb/ChangeLog:

* dwarf2read.c (add_partial_symbol): Do not add a global variable if
its adress is null. Add comment to explain why.
(new_symbol): Ditto.

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 288d777..80222c3 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -3421,7 +3421,19 @@ add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu)
}
break;
case DW_TAG_variable:
- if (pdi->is_external)
+ if (pdi->locdesc)
+ addr = decode_locdesc (pdi->locdesc, cu);
+
+ if (pdi->locdesc
+ && addr == 0
+ && !dwarf2_per_objfile->has_section_at_zero)
+ {
+ /* A global or static variable may also have been stripped
+ out by the linker if unused, in which case its address
+ will be nullified; do not add such variables into partial
+ symbol table then. */
+ }
+ else if (pdi->is_external)
{
/* Global Variable.
Don't enter into the minimal symbol tables as there is
@@ -3436,8 +3448,6 @@ add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu)
used by GDB, but it comes in handy for debugging partial symbol
table building. */

- if (pdi->locdesc)
- addr = decode_locdesc (pdi->locdesc, cu);
if (pdi->locdesc || pdi->has_type)
psym = add_psymbol_to_list (actual_name, strlen (actual_name),
built_actual_name,
@@ -3455,7 +3465,6 @@ add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu)
xfree (actual_name);
return;
}
- addr = decode_locdesc (pdi->locdesc, cu);
/*prim_record_minimal_symbol (actual_name, addr + baseaddr,
mst_file_data, objfile); */
psym = add_psymbol_to_list (actual_name, strlen (actual_name),
@@ -9860,7 +9869,16 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu)
{
var_decode_location (attr, sym, cu);
attr2 = dwarf2_attr (die, DW_AT_external, cu);
- if (attr2 && (DW_UNSND (attr2) != 0))
+ if (SYMBOL_CLASS (sym) == LOC_STATIC
+ && SYMBOL_VALUE_ADDRESS (sym) == 0
+ && !dwarf2_per_objfile->has_section_at_zero)
+ {
+ /* When a static variable is eliminated by the linker,
+ the corresponding debug information is not stripped
+ out, but the variable address is set to null;
+ do not add such variables into symbol table. */
+ }
+ else if (attr2 && (DW_UNSND (attr2) != 0))
{
struct pending **list_to_add;