[Bug debug/26330] New: gcc generates code that does not allow retrieval of struct arguments with debugger

[Bug debug/26330] New: gcc generates code that does not allow retrieval of struct arguments with debugger

[tausq at debian dot org]

Given the following code from gdb's funcargs test:

typedef struct s
{
  short s;
  int i;
  long l;
} SVAL;

void recurse (SVAL a, int depth)
{
  a.s = a.i = a.l = --depth;
  if (depth == 0)
    hitbottom ();
  else
    recurse (a, depth);
}

compiled with -g

gcc-4.0 does not emit a dwarf location for the 'a' argument:

$ readelf -wi funcargs
[....]
 <2><1921>: Abbrev Number: 11 (DW_TAG_formal_parameter)
     DW_AT_name        : a
     DW_AT_decl_file   : 1
     DW_AT_decl_line   : 612
     DW_AT_type        : <18e0>

in gcc-3.x, you will get one more dwarf attribute:
     DW_AT_location    : 3 byte block: 91 18 6  (DW_OP_fbreg: 24; DW_OP_deref)

The difference is that in gcc 3.x, the first argument is first copied from the
incoming argument register to the stack. In gcc-4.x the generated code does not
do this stack save and uses the incoming register directly (actually it first
copies it to a scratch register).


-- 
           Summary: gcc generates code that does not allow retrieval of
                    struct arguments with debugger
           Product: gcc
           Version: 4.0.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tausq at debian dot org
 GCC build triplet: hppa-unknown-linux
  GCC host triplet: hppa-unknown-linux
GCC target triplet: hppa-unknown-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26330

[Bug debug/26330] gcc generates code that does not allow retrieval of struct arguments with debugger

[wilson at gcc dot gnu dot org]

------- Comment #1 from wilson at gcc dot gnu dot org  2006-02-22 03:11 -------
This argument is passed by pointer, converted into a DECL_VALUE_EXPR, and the
DECL_VALUE_EXPR DECL_RTL references a virtual register, which prevents us from
emitting debug info for it.

This looks like the same problem as PR 25562, which is already fixed in gcc-4.1
and mainline.  This patch adds virtual register instantiation support for
DECL_VALUE_EXPR.


-- 

wilson at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |wilson at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26330

[Bug debug/26330] gcc generates code that does not allow retrieval of struct arguments with debugger

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-03-02 12:37 -------
According to known to fail, it fails in 4.1.0 but Jim's comment suggest
otherwise, hmm.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26330

[Bug debug/26330] gcc generates code that does not allow retrieval of struct arguments with debugger

[randolph at tausq dot org]

------- Comment #3 from randolph at tausq dot org  2006-03-02 14:27 -------
Subject: Re:  gcc generates code that does not allow retrieval
 of struct arguments with debugger

pinskia at gcc dot gnu dot org wrote:
> ------- Comment #2 from pinskia at gcc dot gnu dot org  2006-03-02 12:37 -------
> According to known to fail, it fails in 4.1.0 but Jim's comment suggest
> otherwise, hmm.
> 

Yes, with latest gcc-4.1 the problem is gone. Can the relevant patch be 
backported to gcc-4.0?

thanks,
randolph


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26330

[Bug debug/26330] [4.0 only] gcc generates code that does not allow retrieval of struct arguments with debugger

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-debug
      Known to fail|4.0.3 4.1.0                 |4.0.3
            Summary|gcc generates code that does|[4.0 only] gcc generates
                   |not allow retrieval of      |code that does not allow
                   |struct arguments with       |retrieval of struct
                   |debugger                    |arguments with debugger
   Target Milestone|---                         |4.0.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26330

[Bug debug/26330] [4.0 only] gcc generates code that does not allow retrieval of struct arguments with debugger

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.3                       |4.0.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26330

[Bug debug/26330] [4.0 regression] gcc generates code that does not allow retrieval of struct arguments with debugger

[gdr at gcc dot gnu dot org]

------- Comment #4 from gdr at gcc dot gnu dot org  2007-02-03 16:17 -------
Won't fix in GCC-4.0.x.  Closing.


-- 

gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26330