* inconsistency in printing out the value of an unsigned short in gdb
@ 2007-09-25 14:19 Erik Niessen
2007-09-25 15:57 ` Daniel Jacobowitz
0 siblings, 1 reply; 6+ messages in thread
From: Erik Niessen @ 2007-09-25 14:19 UTC (permalink / raw)
To: gdb
Hi all,
I have a simple program:
typedef unsigned short UInt16;
const UInt16 c_uint16 = 0xFE;
UInt16 g_uint16 = 0xFE;
const unsigned short c_ushort = 0xFE;
int main() {
printf("c_ushort=%#X\n",c_ushort);
printf("c_uint16=%#X\n",c_uint16);
printf("g_uint16=%#X\n",g_uint16);
return 0;
}
I use g++ version 4.0 and gdb version 6.6
g++ -g constants.cpp -o ./constants
running this exec gives the following output as expected
c_ushort=0XFE
c_uint16=0XFE
g_uint16=0XFE
But running it in gdb
gdb ./constants
(gdb) b main
(gdb) p /x c_ushort
$1 = 0xfe
(gdb) p /x g_uint16
$2 = 0xfe
(gdb) p /x c_uint16
$3 = 0xfffe
Weird why does it not print the value 0xfe like the other ones.
When I use gcc-4.0 it works as expected
Any ideas??
Cheers,
Erik
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: inconsistency in printing out the value of an unsigned short in gdb
2007-09-25 14:19 inconsistency in printing out the value of an unsigned short in gdb Erik Niessen
@ 2007-09-25 15:57 ` Daniel Jacobowitz
2007-09-26 8:33 ` Erik Niessen
0 siblings, 1 reply; 6+ messages in thread
From: Daniel Jacobowitz @ 2007-09-25 15:57 UTC (permalink / raw)
To: Erik Niessen; +Cc: gdb
On Tue, Sep 25, 2007 at 04:10:51PM +0200, Erik Niessen wrote:
> Any ideas??
Probably inaccurate debug information from your compiler, and
different generated code. The value has been extended for some reason
before GDB got a chance to print it.
--
Daniel Jacobowitz
CodeSourcery
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: inconsistency in printing out the value of an unsigned short in gdb
2007-09-25 15:57 ` Daniel Jacobowitz
@ 2007-09-26 8:33 ` Erik Niessen
2007-09-26 21:38 ` Daniel Jacobowitz
0 siblings, 1 reply; 6+ messages in thread
From: Erik Niessen @ 2007-09-26 8:33 UTC (permalink / raw)
To: gdb
Hi Daniel,
Thanks for your fast reply. I tried with different versions of g++
(3.4.6, 4.0, 4.0.4) they all have the same problem.
Is there a way how I can check the produced debug info for example via objdump?
So that I can convince the g++ people otherwise they will point their
finger at gdb.
Cheers,
Erik
On 9/25/07, Daniel Jacobowitz <drow@false.org> wrote:
> On Tue, Sep 25, 2007 at 04:10:51PM +0200, Erik Niessen wrote:
> > Any ideas??
>
> Probably inaccurate debug information from your compiler, and
> different generated code. The value has been extended for some reason
> before GDB got a chance to print it.
>
> --
> Daniel Jacobowitz
> CodeSourcery
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: inconsistency in printing out the value of an unsigned short in gdb
2007-09-26 8:33 ` Erik Niessen
@ 2007-09-26 21:38 ` Daniel Jacobowitz
2007-09-27 11:27 ` Erik Niessen
0 siblings, 1 reply; 6+ messages in thread
From: Daniel Jacobowitz @ 2007-09-26 21:38 UTC (permalink / raw)
To: Erik Niessen; +Cc: gdb
On Wed, Sep 26, 2007 at 09:35:55AM +0200, Erik Niessen wrote:
> Hi Daniel,
>
> Thanks for your fast reply. I tried with different versions of g++
> (3.4.6, 4.0, 4.0.4) they all have the same problem.
> Is there a way how I can check the produced debug info for example via objdump?
Try readelf -wi.
--
Daniel Jacobowitz
CodeSourcery
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: inconsistency in printing out the value of an unsigned short in gdb
2007-09-26 21:38 ` Daniel Jacobowitz
@ 2007-09-27 11:27 ` Erik Niessen
2007-09-27 12:15 ` Daniel Jacobowitz
0 siblings, 1 reply; 6+ messages in thread
From: Erik Niessen @ 2007-09-27 11:27 UTC (permalink / raw)
To: Erik Niessen, gdb
[-- Attachment #1: Type: text/plain, Size: 659 bytes --]
I ran the readelf -wi on my executable. The output file is attached.
Looking at this debug info all the 3 variables are of type short
unsigned int 2 byte size.
So it looks that the debug info generated by the compiler is correct?
Cheers,
Erik
On 9/26/07, Daniel Jacobowitz <drow@false.org> wrote:
> On Wed, Sep 26, 2007 at 09:35:55AM +0200, Erik Niessen wrote:
> > Hi Daniel,
> >
> > Thanks for your fast reply. I tried with different versions of g++
> > (3.4.6, 4.0, 4.0.4) they all have the same problem.
> > Is there a way how I can check the produced debug info for example via objdump?
>
> Try readelf -wi.
>
> --
> Daniel Jacobowitz
> CodeSourcery
>
[-- Attachment #2: constants++.txt --]
[-- Type: text/plain, Size: 8870 bytes --]
The section .debug_info contains:
Compilation Unit @ offset 0x0:
Length: 118
Version: 2
Abbrev Offset: 0
Pointer Size: 4
<0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
DW_AT_stmt_list : 0
DW_AT_low_pc : 0x8048378
DW_AT_high_pc : 0x804839a
DW_AT_name : ../sysdeps/i386/elf/start.S
DW_AT_comp_dir : /build/buildd/glibc-2.3.6/build-tree/glibc-2.3.6/csu
DW_AT_producer : GNU AS 2.16.91
DW_AT_language : 32769 (MIPS assembler)
Compilation Unit @ offset 0x7a:
Length: 141
Version: 2
Abbrev Offset: 20
Pointer Size: 4
<0><85>: Abbrev Number: 1 (DW_TAG_compile_unit)
DW_AT_stmt_list : 0x5b
DW_AT_high_pc : 0x804839c
DW_AT_low_pc : 0x804839c
DW_AT_producer : (indirect string, offset: 0x62): GNU C 3.4.6 (Ubuntu 3.4.6-1ubuntu2)
DW_AT_language : 1 (ANSI C)
DW_AT_name : (indirect string, offset: 0x0): init.c
DW_AT_comp_dir : (indirect string, offset: 0x11): /build/buildd/glibc-2.3.6/build-tree/glibc-2.3.6/csu
<1><9f>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x90): unsigned int
DW_AT_byte_size : 4
DW_AT_encoding : 7 (unsigned)
<1><a6>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x54): unsigned char
DW_AT_byte_size : 1
DW_AT_encoding : 8 (unsigned char)
<1><ad>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x9d): short unsigned int
DW_AT_byte_size : 2
DW_AT_encoding : 7 (unsigned)
<1><b4>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x8b): long unsigned int
DW_AT_byte_size : 4
DW_AT_encoding : 7 (unsigned)
<1><bb>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x56): signed char
DW_AT_byte_size : 1
DW_AT_encoding : 6 (signed char)
<1><c2>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x7): short int
DW_AT_byte_size : 2
DW_AT_encoding : 5 (signed)
<1><c9>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : int
DW_AT_byte_size : 4
DW_AT_encoding : 5 (signed)
<1><d0>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x46): long long int
DW_AT_byte_size : 8
DW_AT_encoding : 5 (signed)
<1><d7>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x86): long long unsigned int
DW_AT_byte_size : 8
DW_AT_encoding : 7 (unsigned)
<1><de>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x4b): long int
DW_AT_byte_size : 4
DW_AT_encoding : 5 (signed)
<1><e5>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x90): unsigned int
DW_AT_byte_size : 4
DW_AT_encoding : 7 (unsigned)
<1><ec>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0x5d): char
DW_AT_byte_size : 1
DW_AT_encoding : 6 (signed char)
<1><f3>: Abbrev Number: 4 (DW_TAG_variable)
DW_AT_name : (indirect string, offset: 0xb0): _IO_stdin_used
DW_AT_decl_file : 1
DW_AT_decl_line : 25
DW_AT_type : <105>
DW_AT_external : 1
DW_AT_location : 5 byte block: 3 68 85 4 8 (DW_OP_addr: 8048568)
<1><105>: Abbrev Number: 5 (DW_TAG_const_type)
DW_AT_type : <c9>
Compilation Unit @ offset 0x10b:
Length: 140
Version: 2
Abbrev Offset: 86
Pointer Size: 4
<0><116>: Abbrev Number: 1 (DW_TAG_compile_unit)
DW_AT_stmt_list : 0x82
DW_AT_name : /build/buildd/glibc-2.3.6/build-tree/i386-libc/csu/crti.S
DW_AT_comp_dir : /build/buildd/glibc-2.3.6/build-tree/glibc-2.3.6/csu
DW_AT_producer : GNU AS 2.16.91
DW_AT_language : 32769 (MIPS assembler)
Compilation Unit @ offset 0x19b:
Length: 414
Version: 2
Abbrev Offset: 102
Pointer Size: 4
<0><1a6>: Abbrev Number: 1 (DW_TAG_compile_unit)
DW_AT_stmt_list : 0x12f
DW_AT_high_pc : 0x804847e
DW_AT_low_pc : 0x804841c
DW_AT_producer : GNU C++ 3.4.6 (Ubuntu 3.4.6-1ubuntu2)
DW_AT_language : 4 (C++)
DW_AT_name : constants.c
DW_AT_comp_dir : /home/nly99047/sigma/gdb
<1><1ff>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0xbf): unsigned int
DW_AT_byte_size : 4
DW_AT_encoding : 7 (unsigned)
<1><206>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : unsigned char
DW_AT_byte_size : 1
DW_AT_encoding : 8 (unsigned char)
<1><217>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : short unsigned int
DW_AT_byte_size : 2
DW_AT_encoding : 7 (unsigned)
<1><22d>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : long unsigned int
DW_AT_byte_size : 4
DW_AT_encoding : 7 (unsigned)
<1><242>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : signed char
DW_AT_byte_size : 1
DW_AT_encoding : 6 (signed char)
<1><251>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : short int
DW_AT_byte_size : 2
DW_AT_encoding : 5 (signed)
<1><25e>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : int
DW_AT_byte_size : 4
DW_AT_encoding : 5 (signed)
<1><265>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : long long int
DW_AT_byte_size : 8
DW_AT_encoding : 5 (signed)
<1><276>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : long long unsigned int
DW_AT_byte_size : 8
DW_AT_encoding : 7 (unsigned)
<1><290>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : long int
DW_AT_byte_size : 4
DW_AT_encoding : 5 (signed)
<1><29c>: Abbrev Number: 2 (DW_TAG_base_type)
DW_AT_name : (indirect string, offset: 0xbf): unsigned int
DW_AT_byte_size : 4
DW_AT_encoding : 7 (unsigned)
<1><2a3>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : char
DW_AT_byte_size : 1
DW_AT_encoding : 6 (signed char)
<1><2ab>: Abbrev Number: 4 (DW_TAG_typedef)
DW_AT_name : UInt16
DW_AT_decl_file : 1
DW_AT_decl_line : 4
DW_AT_type : <217>
<1><2b9>: Abbrev Number: 5 (DW_TAG_subprogram)
DW_AT_external : 1
DW_AT_name : main
DW_AT_decl_file : 1
DW_AT_decl_line : 12
DW_AT_type : <25e>
DW_AT_low_pc : 0x804841c
DW_AT_high_pc : 0x804847e
DW_AT_frame_base : 1 byte block: 55 (DW_OP_reg5)
<1><2d0>: Abbrev Number: 6 (DW_TAG_namespace)
DW_AT_sibling : <311>
DW_AT_name : ::
DW_AT_decl_file : 2
DW_AT_decl_line : 0
<2><2da>: Abbrev Number: 7 (DW_TAG_variable)
DW_AT_name : c_uint16
DW_AT_decl_file : 1
DW_AT_decl_line : 5
DW_AT_type : <311>
DW_AT_declaration : 1
DW_AT_const_value : 254
<2><2ec>: Abbrev Number: 8 (DW_TAG_variable)
DW_AT_name : g_uint16
DW_AT_decl_file : 1
DW_AT_decl_line : 6
DW_AT_type : <2ab>
DW_AT_external : 1
DW_AT_declaration : 1
<2><2fe>: Abbrev Number: 7 (DW_TAG_variable)
DW_AT_name : c_ushort
DW_AT_decl_file : 1
DW_AT_decl_line : 8
DW_AT_type : <32c>
DW_AT_declaration : 1
DW_AT_const_value : 254
<1><311>: Abbrev Number: 9 (DW_TAG_const_type)
DW_AT_type : <2ab>
<1><316>: Abbrev Number: 10 (DW_TAG_variable)
DW_AT_specification: <2da>
DW_AT_location : 5 byte block: 3 96 85 4 8 (DW_OP_addr: 8048596)
<1><321>: Abbrev Number: 10 (DW_TAG_variable)
DW_AT_specification: <2ec>
DW_AT_location : 5 byte block: 3 8 97 4 8 (DW_OP_addr: 8049708)
<1><32c>: Abbrev Number: 9 (DW_TAG_const_type)
DW_AT_type : <217>
<1><331>: Abbrev Number: 10 (DW_TAG_variable)
DW_AT_specification: <2fe>
DW_AT_location : 5 byte block: 3 98 85 4 8 (DW_OP_addr: 8048598)
Compilation Unit @ offset 0x33d:
Length: 140
Version: 2
Abbrev Offset: 241
Pointer Size: 4
<0><348>: Abbrev Number: 1 (DW_TAG_compile_unit)
DW_AT_stmt_list : 0x181
DW_AT_name : /build/buildd/glibc-2.3.6/build-tree/i386-libc/csu/crtn.S
DW_AT_comp_dir : /build/buildd/glibc-2.3.6/build-tree/glibc-2.3.6/csu
DW_AT_producer : GNU AS 2.16.91
DW_AT_language : 32769 (MIPS assembler)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: inconsistency in printing out the value of an unsigned short in gdb
2007-09-27 11:27 ` Erik Niessen
@ 2007-09-27 12:15 ` Daniel Jacobowitz
0 siblings, 0 replies; 6+ messages in thread
From: Daniel Jacobowitz @ 2007-09-27 12:15 UTC (permalink / raw)
To: Erik Niessen; +Cc: gdb
On Thu, Sep 27, 2007 at 12:41:37PM +0200, Erik Niessen wrote:
> I ran the readelf -wi on my executable. The output file is attached.
> Looking at this debug info all the 3 variables are of type short
> unsigned int 2 byte size.
> So it looks that the debug info generated by the compiler is correct?
That's not the issue. You need to look at where the .debug_info
section says the variables live (DW_AT_location), and compare it
to what the assembly code is putting there.
--
Daniel Jacobowitz
CodeSourcery
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2007-09-27 12:07 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-09-25 14:19 inconsistency in printing out the value of an unsigned short in gdb Erik Niessen
2007-09-25 15:57 ` Daniel Jacobowitz
2007-09-26 8:33 ` Erik Niessen
2007-09-26 21:38 ` Daniel Jacobowitz
2007-09-27 11:27 ` Erik Niessen
2007-09-27 12:15 ` Daniel Jacobowitz
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox