Re: other/5554: corrupt this pointer after function call

[Andrew Pinski <pinskia at physics dot uc dot edu>]

The following reply was made to PR other/5554; it has been noted by GNATS.

From: Andrew Pinski <pinskia@physics.uc.edu>
To: jeroenk@allieddata.com
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: other/5554: corrupt this pointer after function call
Date: Thu, 31 Jan 2002 09:31:27 -0500

 Try a newer version of gcc and/or gdb. It seems to fixed in ones build 
 yesterday.
 
 Thanks,
 Andrew Pinski
 On Thursday, January 31, 2002, at 09:08 , jeroenk@allieddata.com wrote:
 
 >
 >> Number:         5554
 >> Category:       other
 >> Synopsis:       corrupt this pointer after function call
 >> Confidential:   no
 >> Severity:       serious
 >> Priority:       medium
 >> Responsible:    unassigned
 >> State:          open
 >> Class:          sw-bug
 >> Submitter-Id:   net
 >> Arrival-Date:   Thu Jan 31 06:16:00 PST 2002
 >> Closed-Date:
 >> Last-Modified:
 >> Originator:     jeroenk@allieddata.com
 >> Release:        3.1
 >> Organization:
 >> Environment:
 >
 >> Description:
 > Hello,
 >
 > My this pointer becomes corrupt after a function call.
 >
 > I use the following:
 > - gcc & g++ version 3.1
 > - libstdc++-3.1-0.17
 > - glibc-2.2.90-3
 >
 > In the debugger (gdb) you can see how the this pointer becommes corrupt.
 > Before we call the function we use a backtrace (bt) to resolve the this 
 > pointer: (0x08048502 in Test::test() (this=0xbffff9e0) )
 > After executing the function the this pointer has changed:(0x08048502 
 > in Test::test() (this=0xbffff9e5))
 >
 > ______________________________________________________________________
 > GNU gdb Red Hat Linux (5.1-2)
 > Copyright 2001 Free Software Foundation, Inc.
 > GDB is free software, covered by the GNU General Public License, and 
 > you are
 > welcome to change it and/or distribute copies of it under certain 
 > conditions.
 > Type "show copying" to see the conditions.
 > There is absolutely no warranty for GDB.  Type "show warranty" for 
 > details.
 > This GDB was configured as "i386-redhat-linux"...
 > (gdb) break 31
 > Breakpoint 1 at 0x8048511: file test2.cpp, line 31.
 > (gdb) run
 > Starting program: /home/jeroenk/qt/monitor/test/test2/./test2
 >
 > Breakpoint 1, Test::SetCurrentMACaddress(unsigned char*) 
 > (this=0xbffff9e0,
 >     TheCurrentMACaddress=0xbffff9b0 
 > "\001\002\003\004\005\006\001@\210\226\001@\005")
 >     at test2.cpp:31
 > 31          memcpy(CurrentMACaddress, TheCurrentMACaddress, sizeof 
 > (CurrentMACaddress));
 > (gdb) bt
 > #0  Test::SetCurrentMACaddress(unsigned char*) (this=0xbffff9e0,
 >     TheCurrentMACaddress=0xbffff9b0 
 > "\001\002\003\004\005\006\001@\210\226\001@\005")
 >     at test2.cpp:31
 > #1  0x08048502 in Test::test() (this=0xbffff9e0) at test2.cpp:26
 > #2  0x08048572 in main (argc=1, argv=0xbffffa54) at test2.cpp:51
 > #3  0x4011e108 in __libc_start_main () from /lib/i686/libc.so.6
 > (gdb) next
 > 32      }
 > (gdb) bt
 > #0  Test::SetCurrentMACaddress(unsigned char*) (this=0xbffff9e0,
 >     TheCurrentMACaddress=0xbffff9b0 
 > "\001\002\003\004\005\006\001@\210\226\001@\005")
 >     at test2.cpp:32
 > #1  0x08048502 in Test::test() (this=0xbffff9e5) at test2.cpp:26
 > #2  0x08048572 in main (argc=1, argv=0xbffffa54) at test2.cpp:51
 > #3  0x4011e108 in __libc_start_main () from /lib/i686/libc.so.6
 > (gdb)
 > ____________________________________________________________________________
 >
 > However if we use the another pc with the following information:
 > gcc & g++ version 2.96
 > libstdc++-2.96-98
 > glibc-2.2.4-19.3
 >
 > Everyting works fine.
 > ____________________________________________________________________________
 > GNU gdb Red Hat Linux (5.1-1)
 > Copyright 2001 Free Software Foundation, Inc.
 > GDB is free software, covered by the GNU General Public License, and 
 > you are
 > welcome to change it and/or distribute copies of it under certain 
 > conditions.
 > Type "show copying" to see the conditions.
 > There is absolutely no warranty for GDB.  Type "show warranty" for 
 > details.
 > This GDB was configured as "i386-redhat-linux"...
 > (gdb) break 31
 > Breakpoint 1 at 0x804856d: file test2.cpp, line 31.
 > (gdb) run
 > Starting program: /home/jeroenk/./test2
 >
 > Breakpoint 1, Test::SetCurrentMACaddress (this=0xbffff9f0,
 >     TheCurrentMACaddress=0xbffff9c0 "\001\002\003\004\005\006") at 
 > test2.cpp:31
 > 31          memcpy(CurrentMACaddress, TheCurrentMACaddress, sizeof 
 > (CurrentMACaddress));
 > (gdb) bt
 > #0  Test::SetCurrentMACaddress (this=0xbffff9f0,
 >     TheCurrentMACaddress=0xbffff9c0 "\001\002\003\004\005\006") at 
 > test2.cpp:31
 > #1  0x0804855e in Test::test (this=0xbffff9f0) at test2.cpp:26
 > #2  0x080485d2 in main (argc=1, argv=0xbffffa74) at test2.cpp:51
 > #3  0x400b4627 in __libc_start_main (main=0x80485c0 <main>, argc=1, 
 > ubp_av=0xbffffa74,
 >     init=0x80483bc <_init>, fini=0x8048620 <_fini>, 
 > rtld_fini=0x4000dcc4 <_dl_fini>,
 >     stack_end=0xbffffa6c) at ../sysdeps/generic/libc-start.c:129
 > (gdb) next
 > 32      }
 > (gdb) bt
 > #0  Test::SetCurrentMACaddress (this=0xbffff9f0,
 >     TheCurrentMACaddress=0xbffff9c0 "\001\002\003\004\005\006") at 
 > test2.cpp:32
 > #1  0x0804855e in Test::test (this=0xbffff9f0) at test2.cpp:26
 > #2  0x080485d2 in main (argc=1, argv=0xbffffa74) at test2.cpp:51
 > #3  0x400b4627 in __libc_start_main (main=0x80485c0 <main>, argc=1, 
 > ubp_av=0xbffffa74,
 >     init=0x80483bc <_init>, fini=0x8048620 <_fini>, 
 > rtld_fini=0x4000dcc4 <_dl_fini>,
 >     stack_end=0xbffffa6c) at ../sysdeps/generic/libc-start.c:129
 > (gdb)
 > ___________________________________________________________________________
 >
 > See also attached source file.
 >
 > What could be the problem?
 >> How-To-Repeat:
 > see description and file attachment
 > If file attachment fails, see source code below:
 > -----test2.cpp------
 > #include <stddef.h>
 >
 > typedef unsigned       char tMAC[6];
 >
 > class Test{
 >
 > public:
 >     void test();
 > private:
 >     void SetCurrentMACaddress(tMAC TheCurrentMACaddress);
 >     void *memcpy(void *dest, const void *src, size_t n);
 >     tMAC CurrentMACaddress;
 >
 > };
 >
 > void Test::test()
 > {
 >     tMAC MyMac;
 >     MyMac[0] = 0x01;
 >     MyMac[1] = 0x02;
 >     MyMac[2] = 0x03;
 >     MyMac[3] = 0x04;
 >     MyMac[4] = 0x05;
 >     MyMac[5] = 0x06;
 >
 >     SetCurrentMACaddress(MyMac);
 > }
 >
 > void Test::SetCurrentMACaddress(tMAC TheCurrentMACaddress)
 > {
 >     memcpy(CurrentMACaddress, TheCurrentMACaddress, sizeof 
 > (CurrentMACaddress));
 > }
 >
 > void *Test::memcpy(void *dest, const void *src, size_t n)
 > {
 >     void * tmp = dest;
 >
 >     while(n--)
 >     {
 >        *((char *)dest) = *((char *)src);
 >        ++(char *)dest;
 >        ++(char *)src;
 >     }
 >    return tmp;
 > }
 >
 > int main( int argc, char ** argv )
 > {
 >     Test a;
 >
 >     a.test();
 > }
 > -----test2.cpp------
 >> Fix:
 > None
 >> Release-Note:
 >> Audit-Trail:
 >> Unformatted:
 >
 >