Re: symtab/2323: gdwarf-2 register params with backing store cannot be displayed

Re: symtab/2323: gdwarf-2 register params with backing store cannot be displayed

[drow]

Synopsis: gdwarf-2 register params with backing store cannot be displayed

State-Changed-From-To: open->closed
State-Changed-By: drow
State-Changed-When: Sat Sep 29 20:27:25 2007
State-Changed-Why:
    I've concluded that the debug information is incorrect.

http://sourceware.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gdb&pr=2323

Re: symtab/2323: gdwarf-2 register params with backing store cannot be displayed

[Daniel Jacobowitz]

The following reply was made to PR symtab/2323; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@false.org>
To: mblower@chipwrights.com
Cc: gdb-gnats@sources.redhat.com
Subject: Re: symtab/2323: gdwarf-2 register params with backing store
	cannot be displayed
Date: Fri, 28 Sep 2007 09:27:24 -0400

 On Fri, Sep 28, 2007 at 01:12:35PM -0000, mblower@chipwrights.com wrote:
 > Using -gdwarf-2 to build debug information, when break inside "stow_it", cannot display parameter r4, instead gdb gets an error stating "Asking for position 0 of stack, stack only contains 0 elements."  Similar difficulty with "info frame" and some of the other expression display commands. If I rebuild with -gstabs then gdb does not have this difficulty.
 
 What compiler and version are you using?  This is probably a symptom
 of incorrect debugging information emitted by your compiler.
 
 The output of readelf -wio on the binary might help.
 
 -- 
 Daniel Jacobowitz
 CodeSourcery

symtab/2323: gdwarf-2 register params with backing store cannot be displayed

[mblower]

>Number:         2323
>Category:       symtab
>Synopsis:       gdwarf-2 register params with backing store cannot be displayed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 28 13:18:02 UTC 2007
>Closed-Date:
>Last-Modified:
>Originator:     mblower@chipwrights.com
>Release:        gdb 6.6 --target=arm-softfloat-elf
>Organization:
>Environment:
redhat linux 7.0, also pc-cygwin, build the c executable with eclipse cdt plugin 200707121445, 
>Description:
Using -gdwarf-2 to build debug information, when break inside "stow_it", cannot display parameter r4, instead gdb gets an error stating "Asking for position 0 of stack, stack only contains 0 elements."  Similar difficulty with "info frame" and some of the other expression display commands. If I rebuild with -gstabs then gdb does not have this difficulty.

I'm not including all the runtime support stuff--hopefully this is sufficient for you to reconstruct the error. I think the bug is that gdb doesn't know how to decode the dwarf for the param r4. I stepped through gdb, and in evaluating r4 it went into dwarf2_evaluate_loc_desc where I would think it should fall into the "if ctx->in_reg" clause, but it didn't.
>How-To-Repeat:
gdb foo.elf
target sim
break stow_it
load
run
Here's the build info:
**** Build of configuration Release for project test-ipc-armSide ****

make -k all 
Building file: H:/views/swapps/chipSupport/ipc/test/arm_main.c
Invoking: C Compiler
arm-elf-gcc -mcpu=arm926ej-s -D__CW5631__ -D__CWARM__ -I../../../../../../commonIncludes -I../../../../../armSupport/inc -I../../../sampleCode/armSamples/inc/cas -I../../../sampleCode/armSamples/inc/cas_lib -I../../../sampleCode/armSamples/inc/shared_c -I../../../sampleCode/armSamples/inc -I../../../../../chipDefs -I../../../../../ipc -I../../../../../rpc -O1 -gdwarf-2 -Wall -c -mfpu=fpa --freestanding -mlong-calls -Wa,-mapcs-32 -o"arm_main.o" "H:/views/swapps/chipSupport/ipc/test/arm_main.c" && \
echo -n 'arm_main.d' ./ > 'arm_main.d' && \
arm-elf-gcc -MM -MG -P -w -mcpu=arm926ej-s -D__CW5631__ -D__CWARM__ -I../../../../../../commonIncludes -I../../../../../armSupport/inc -I../../../sampleCode/armSamples/inc/cas -I../../../sampleCode/armSamples/inc/cas_lib -I../../../sampleCode/armSamples/inc/shared_c -I../../../sampleCode/armSamples/inc -I../../../../../chipDefs -I../../../../../ipc -I../../../../../rpc -O1 -gdwarf-2 -Wall -c -mfpu=fpa --freestanding -mlong-calls -Wa,-mapcs-32  "H:/views/swapps/chipSupport/ipc/test/arm_main.c" >> 'arm_main.d'
H:/views/swapps/chipSupport/ipc/test/arm_main.c: In function 'arm_main':
H:/views/swapps/chipSupport/ipc/test/arm_main.c:58: warning: implicit declaration of function 'my_quit'
H:/views/swapps/chipSupport/ipc/test/arm_main.c: In function 'puts':
H:/views/swapps/chipSupport/ipc/test/arm_main.c:101: warning: passing argument 1 of 'my_strlen' discards qualifiers from pointer target type
H:/views/swapps/chipSupport/ipc/test/arm_main.c: At top level:
H:/views/swapps/chipSupport/ipc/test/arm_main.c:31: warning: 'dram_buff' defined but not used
Finished building: H:/views/swapps/chipSupport/ipc/test/arm_main.c
 
Building target: test-ipc.elf
Invoking: C Linker
arm-elf-ld  ./arm_main.o    -o"test-ipc.elf" -T"../../../arm_ipc_test.lcf" -nostdlib -static -lArmSupport -L../../../../../armSupport/projects/armSupport/Release -Map=test-ipc.map
Finished building target: test-ipc.elf
 
make --no-print-directory post-build
pwd
/cygdrive/h/views/swapps/chipSupport/ipc/test/projects/test-ipc-armSide/Release
 
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="arm_main.c"
Content-Disposition: inline; filename="arm_main.c"

#include <stdio.h>
#include <string.h>

char output_vec[10000];
int outP = 0;

void my_printf(char *s)
{
    while(s){ output_vec[outP++] = s++; }
}

extern int vec[];
int vec[8];

void stow_it( int r1, int r2, int r3, int r4, int r5, int r6, int r7, int r8)
{
	
	vec[0]=r1;
		vec[1]=r2;
		vec[2]=r3;
		vec[3]=r4;
		vec[5]=r5;
			vec[6]=r6;
			vec[7]=r7;
			vec[8]=r8;
}

void bye()
{
    /* quit here */
}

main()
{
    my_printf("calling stow it\n");
    stow_it(1,2,3,4,5,6,7,8);
    my_printf("calling stow it again\n");
    stow_it(1,2,3,4,5,6,7,8);
    my_printf("bye\n");
    bye();
}