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Re: Problem with location lists and variables on stack


> > Let the local variables and (some) arguments be addressed using stack pointer,
> > for example x86-64 architecture with variables addressed using %rsp.
> > The address emitted for variables located on stack by my new patch is always
> > DW_OP_fbreg + constant.
> > 
> > When I was testing the emitted debug info with mainline GDB I found that
> > GDB probably does not adjust addresses of variables when stack pointer changes
> > (like because of "pushq" instruction) if using location lists.
> > I think GDB should adjust the address of %rsp addressed variables according to
> > change of %rsp (probably DWARF2 sais so for DW_OP_fbreg). I think it is a
> > better solution than emitting new locations to location list for all variables
> > located on stack after each "push" and "pop" which would cause too large debug
> > info.
> > 
> > When I looked to gdb/dwarf2loc.c I see there:
> >  /* FIXME: cagney/2003-03-26: This code should be using
> >      get_frame_base_address(), and then implement a dwarf2 specific
> >      this_base method.  */
> > Probably this is related to my problem.
> 
> The FIXME is a cleanliness problem.  We do evaluate DW_AT_frame_base,
> so it _ought_ to work.
> 
> > I tested it on attached C file, assembler with debug info and x86-64 binary
> > is attached too.
> 
> Do you suppose you could produce an x86 (ia32) testcase?  I don't have
> x86-64 hardware available yet.  The debug info looks right so I'd like
> to get my fingers into the problem.

Here is the x86 assembler.

Josef

Attachment: m-i386.s
Description: Text document

Attachment: m-i386
Description: Binary data


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