Re: [PATCH] testsuite/gdb.dwarf2: Fix for dw2-ifort-parameter failure on ARM

[Omair Javaid <omair dot javaid at linaro dot org>]

On Thu 16 Jan 2014 05:35:46 PM PKT, Pedro Alves wrote:
> On 01/16/2014 10:26 AM, Omair Javaid wrote:
>>
>>
>> On 01/16/2014 02:48 PM, Pedro Alves wrote:
>>> On 01/16/2014 09:03 AM, Omair Javaid wrote:
>>>
>>>> There seemed no problem with how breakpoint addresses were being adjusted. 
>>>> This test requires to build dwarf info by hand in dw2-ifort-parameter-debug.S
>>>> using compile time addresses so in case of arm (thumb mode) the least
>>>> significant bits of compile time address are set to 1. For that reason 
>>>> 0x000083bd was being used as a breakpoint address func. 
>>>
>>> OOC, what does the compiler debug info usually do instead to avoid this?
>>>
>>
>> Here is what compiler generates when there are thumb functions to handle:
>>         .thumb_func
>>         .type func, %function
>> func:
>> .LFB0:
>>
>> func is marked as thumb function and thus this func pointer will have the 
>> lower bit set. While .LFB0: non thumb label will be used to mark function
>> start address. Like this:         .4byte .LFB0 @ DW_AT_low_pc
>
> Ah.  I wonder if this works for you (and everyone).
>
> ---
>  gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter-debug.S | 4 ++--
>  gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.c       | 6 ++++++
>  2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter-debug.S b/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter-debug.S
> index c7dd9be..6b08cb2 100644
> --- a/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter-debug.S
> +++ b/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter-debug.S
> @@ -35,8 +35,8 @@
>  	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
>  	.byte		1			/* DW_AT_external */
>  	.ascii		"func\0"		/* DW_AT_name */
> -	.4byte		func			/* DW_AT_low_pc */
> -	.4byte		main			/* DW_AT_high_pc */
> +	.4byte		func_addr		/* DW_AT_low_pc */
> +	.4byte		main_addr		/* DW_AT_high_pc */
>  
>  	.uleb128	3			/* Abbrev: DW_TAG_formal_parameter */
>  	.ascii		"param\0"		/* DW_AT_name */
> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.c b/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.c
> index 361c44d..c866b0f 100644
> --- a/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.c
> +++ b/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter.c
> @@ -29,3 +29,9 @@ main (void)
>    func ();
>    return 0;
>  }
> +
> +/* Addresses represented as data symbols, thus without Thumb (etc.)
> +   mode bits.  The dw2-ifort-parameter-debug.S file uses this as
> +   func's low_pc/high_pc.  */
> +extern void *func_addr __attribute__ ((alias ("func")));
> +extern void *main_addr __attribute__ ((alias ("main")));

Patch doesnt fix the issue and builds after making changes to alias definition like:

extern void func_addr() __attribute__ ((alias ("func")));
extern void main_addr() __attribute__ ((alias ("main")));

I have actually tried similar stuff before by adding:

asm(".globl func_addr");
asm(".4byte func_addr");

but issues remains the same.

Heres the output with your patch:

warning: Breakpoint address adjusted from 0x000083c5 to 0x000083c4.
Breakpoint 1 at 0x83c4 (2 locations)
(gdb) run 
Starting program: /home/omair/gdb_dev/gdb/gdb/testsuite/gdb.dwarf2/dw2-ifort-parameter 
warning: Breakpoint address adjusted from 0x000083c5 to 0x000083c4.
warning: Breakpoint address adjusted from 0x000083c5 to 0x000083c4.
warning: Breakpoint address adjusted from 0x000083c5 to 0x000083c4.
warning: Breakpoint 1 address previously adjusted from 0x000083c5 to 0x000083c4.

Breakpoint 1, 0x000083c4 in func_addr ()
(gdb) p/x param
No symbol "param" in current context.
(gdb) FAIL: gdb.dwarf2/dw2-ifort-parameter.exp: p/x param
testcase ./gdb.dwarf2/dw2-ifort-parameter.exp completed in 1 seconds