From: Manoj Iyer <manjo@austin.ibm.com>
To: gdb@sources.redhat.com
Subject: gdb unable to print fn argument correctly
Date: Thu, 21 Jul 2005 20:06:00 -0000 [thread overview]
Message-ID: <Pine.LNX.4.58.0507211343470.620@lazy> (raw)
I have an test program which has a function of the nature 'void fn(double
c){}', which is compiled as a PwerPC 64bit application. When I set a
breakpoint and stop on this function, GDB is not printing the arguments
passed to this function correctly.
I did some initial debugging, the dwarf information and dissassembly of
the function looks good to me. But I am not able to pin point who is
corrupting the stack. I believe gdb is just printing what is avaiable in
the stack to output.
Any pointers to help me identify the culprit deeply appreciated.
============= test.c ========================
#include <stdio.h>
void fn1(int a) {}
void fn2(long b){}
void fn3(double c){}
int
main()
{
fn1(1234);
fn2(123456789L);
fn3(1234.4567);
return 0;
}
============= end test.c ======================
============= GDB output ======================
(gdb) br main
Breakpoint 1 at 0x10000574: file /tmp/test1.c, line 10.
(gdb) br fn3
Breakpoint 2 at 0x10000544: file /tmp/test1.c, line 5.
(gdb) r
Starting program: /tmp/test.gdb
Breakpoint 1, main () at /tmp/test1.c:10
10 fn1(1234);
(gdb) c
Continuing.
Breakpoint 2, 0x0000000010000544 in fn3 (c=6.0995758190771502e-316)
at /tmp/test1.c:5
5 void fn3(double c){}
(gdb)
================= end gdb output ==========================
When I change this testcase, change function fn3 to have something
meaningful in the body, gdb prints the arguments correctly.
=================== modified test.c ======================
#include <stdio.h>
void fn1(int a) {}
void fn2(long b){}
void fn3(double c){printf("hello world %lf\n", c);}
int
main()
{
fn1(1234);
fn2(123456789L);
fn3(1234.4567);
return 0;
}
================= end of test.c ==========================
================= output from gdb =======================
(gdb) br main
Breakpoint 1 at 0x100004c0: file test.c, line 9.
(gdb) br fn3
Breakpoint 2 at 0x10000488: file test.c, line 5.
(gdb) r
Starting program: /tmp/test
Breakpoint 1, main () at test.c:9
warning: Source file is more recent than executable.
9 fn1(1234);
(gdb) c
Continuing.
Breakpoint 2, fn3 (c=1234.4567) at test.c:5
5 void fn3(double c){printf("hello world %lf\n", c);}
(gdb)
================== end of output from gdb ===================
=================== DWARF info for fn3() ===================
<1><2bf>: Abbrev Number: 4 (DW_TAG_subprogram)
DW_AT_sibling : <2e3>
DW_AT_external : 1
DW_AT_name : fn3
DW_AT_decl_file : 1
DW_AT_decl_line : 5
DW_AT_prototyped : 1
DW_AT_low_pc : 0x10000448 268436552
DW_AT_high_pc : 0x10000468 268436584
DW_AT_frame_base : 1 byte block: 6f (DW_OP_reg31)
<2><2d6>: Abbrev Number: 5 (DW_TAG_formal_parameter)
DW_AT_name : c
DW_AT_decl_file : 1
DW_AT_decl_line : 5
DW_AT_type : <2e3>
DW_AT_location : 2 byte block: 91 8 (DW_OP_fbreg: 8)
<1><2e3>: Abbrev Number: 3 (DW_TAG_base_type)
DW_AT_name : double
DW_AT_byte_size : 8
DW_AT_encoding : 4 (float)
=================================================================
==== Disassembly of void fn3(double c){} =======================
fn3()
[5] 10000448: 94 21 ff e0 stwu r1, -32(r1)
1000044c: 93 e1 00 1c stw r31, 28(r1)
10000450: 7c 3f 0b 78 mr r31, r1
10000454: d8 3f 00 08 stfd fr1, 8(r31)
10000458: 81 61 00 00 lwz r11, 0(r1)
1000045c: 83 eb ff fc lwz r31, -4(r11)
10000460: 7d 61 5b 78 mr r1, r11
10000464: 4e 80 00 20 blr
==================================================================
Thanks
-----
manjo
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Cogito ergo sum +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
next reply other threads:[~2005-07-21 20:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-21 20:06 Manoj Iyer [this message]
2005-07-21 20:10 ` Daniel Jacobowitz
2005-07-21 22:55 ` Manoj Iyer
2005-07-21 22:59 ` Daniel Jacobowitz
2005-07-26 18:44 ` Manoj Iyer
2005-07-27 18:10 ` Daniel Jacobowitz
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