Stepping into my compiled libnetsnmpagent.so.5 with gdb when there is a

#1 (**permalink**) 02-18-2005

<html><body>
Hi, 
I am very new to net-snmp and to linux...just what you guys wanted to h=
ear, right? Anyway, I am sure there is a simple answer for this but I h=
ave been beating my head against the wall the past few days so if some =
one could take time to explain how to step into a shared library with g=
db, I would very much appreciate it. There is a short version of the qu=
estion, and a long version below. 
 
My short question is: 
How do I set up the environment to allow me to step into my compiled ve=
rsion libnetsnmpagent.so.5 with gdb when there is a system shared libra=
ry of the same name in the system path? Is there an environment variabl=
e in gdb I need to set to have it pick up the right shared module? I t=
ried static linking but I got lost in a maze of link order problems. I =
would rather get the dynamic debugging going but I am open to static li=
nking if some one could help with the link order. That is a whole other=
post though....thanks for the help. 
 
Thanks for the help, 
 
Alan L. Anderson 
RadiSys 
alan.anderson@radisys.com 
 
************** The same question in long format with research *********=
************** 
It seems that when I set the dynamic linker environment variables to ve=
rbose: 
setenv LD_VERBOSE t 
setenv LD_TRACE_LOADED_OBJECTS t 
setenv LD_WARN t 
 
I get what I expect. Before the LD_LIBRARY_PATH is set, I get this.
<ul>bld1-dsm> pwd 
/vobs/vob3/net-snmp/doc/tutorial 
bld1-dsm> ./example-demon 
libnetsnmpagent.so.5 =3D> /usr/lib/libnetsnmpagent.so.5 (0x4=
0023000) 
libnetsnmpmibs.so.5 =3D> /usr/lib/libnetsnmpmibs.so.5 (0x400=
3a000) 
libnetsnmphelpers.so.5 =3D> /usr/lib/libnetsnmphelpers.so.5 =
(0x400d5000) 
libnetsnmp.so.5 =3D> /usr/lib/libnetsnmp.so.5 (0x400e6000)<b=
r>
libdl.so.2 =3D> /lib/libdl.so.2 (0x40167000) 
libcrypto.so.4 =3D> /lib/libcrypto.so.4 (0x4016b000) 
libm.so.6 =3D> /lib/tls/libm.so.6 (0x4025d000) 
libc.so.6 =3D> /lib/tls/libc.so.6 (0x42000000) 
/lib/ld-linux.so.2 =3D> /lib/ld-linux.so.2 (0x40000000) 
libgssapi_krb5.so.2 =3D> /usr/kerberos/lib/libgssapi_krb5.so=
..2 (0x4027f000 
) 
libkrb5.so.3 =3D> /usr/kerberos/lib/libkrb5.so.3 (0x40292000=
) 
libcom_err.so.3 =3D> /usr/kerberos/lib/libcom_err.so.3 (0x40=
2f0000) 
libk5crypto.so.3 =3D> /usr/kerberos/lib/libk5crypto.so.3 (0x=
402f2000) 
libresolv.so.2 =3D> /lib/libresolv.so.2 (0x40303000) 
libz.so.1 =3D> /usr/lib/libz.so.1 (0x40315000) 
</ul>
After the LD_LIBRARY_PATH is set, I get this:
<ul>bld1-dsm> printenv LD_LIBRARY_PATH /vobs/vob3/net-snmp/tfs/x86/a=
gent/.libs:/vobs/vob3/net-snmp/tfs/x86/snmplib/.libs:/vobs/vob3/net-snm=
p/tfs/x86/agent/helpers/.libs:/usr/X11R5/lib:/usr/MOTIF/lib 
bld1-dsm> 
 
/vobs/vob3/net-snmp/doc/tutorial 
bld1-dsm> ./example-demon 
libnetsnmpagent.so.5 =3D> /vobs/vob3/net-snmp/tfs/x86/agent/=
..libs/libnetsnmpagent.so.5 (0x40017000) 
libnetsnmpmibs.so.5 =3D> /vobs/vob3/net-snmp/tfs/x86/agent/.=
libs/libnetsnmpmibs.so.5 (0x40048000) 
libnetsnmphelpers.so.5 =3D> /vobs/vob3/net-snmp/tfs/x86/agen=
t/helpers/.libs/libnetsnmphelpers.so.5 (0x400d4000) 
libnetsnmp.so.5 =3D> /vobs/vob3/net-snmp/tfs/x86/snmplib/.li=
bs/libnetsnmp.so.5 (0x400ec000) 
libdl.so.2 =3D> /lib/libdl.so.2 (0x40189000) 
libcrypto.so.4 =3D> /lib/libcrypto.so.4 (0x4018d000) 
libm.so.6 =3D> /lib/tls/libm.so.6 (0x4027f000) 
libc.so.6 =3D> /lib/tls/libc.so.6 (0x42000000) 
/lib/ld-linux.so.2 =3D> /lib/ld-linux.so.2 (0x40000000) 
libgssapi_krb5.so.2 =3D> /usr/kerberos/lib/libgssapi_krb5.so=
..2 (0x402a1000 
) 
libkrb5.so.3 =3D> /usr/kerberos/lib/libkrb5.so.3 (0x402b4000=
) 
libcom_err.so.3 =3D> /usr/kerberos/lib/libcom_err.so.3 (0x40=
312000) 
libk5crypto.so.3 =3D> /usr/kerberos/lib/libk5crypto.so.3 (0x=
40314000) 
libresolv.so.2 =3D> /lib/libresolv.so.2 (0x40325000) 
libz.so.1 =3D> /usr/lib/libz.so.1 (0x40337000) 
</ul>
All seems to be cool. But when I try to set a break point in init_agent=
(resolved in file
<ul>bld1-dsm> gdb example-demon 
GNU gdb Red Hat Linux (5.3post-0.20021129.18rh) 
Copyright 2003 Free Software Foundation, Inc. 
GDB is free software, covered by the GNU General Public License, and yo=
u are 
welcome to change it and/or distribute copies of it under certain condi=
tions. 
Type "show copying" to see the conditions. 
There is absolutely no warranty for GDB. Type "show warranty&quot=
; for details. 
This GDB was configured as "i386-redhat-linux-gnu"... 
(gdb) dir /vobs/vob3/net-snmp/src/agent/:/vobs/vob3/net-snmp/src/agent/=
helpers:/vobs/vob3/net-snmp/src/snmplib:/vobs/vob3/net-snmp/doc/tutoria=
l 
Source directories searched: /vobs/vob3/net-snmp/src/agent:/vobs/vob3/n=
et-snmp/src/agent/helpers:/vobs/vob3/net-snmp/src/snmplib:/vobs/vob3/ne=
t-snmp/doc/tutorial:$cdir:$cwd 
(gdb) 
(gdb) b main 
Breakpoint 1 at 0x8048860: file example-demon.c, line 25. 
(gdb) b init_agent 
Breakpoint 2 at 0x80486c8 
(gdb) run 
Starting program: /vobs/vob3/net-snmp/doc/tutorial/example-demon 
..cshrc 
Terminal type? [xterm] 
Erase is control-H (^H). 
Kill is control-X (^X). 
Breakpoint 2 at 0x4002d714 
 
Breakpoint 1, main (argc=3D1, argv=3D0xbffff064) at example-demon.c:25<=
br>
25 snmp_enable_stderrlog(); 
(gdb) next 
30 netsnmp_ds_set_boolean(NETSNMP_DS_APPLICATION_ID, NETSNMP_D=
S_AGENT_ROLE, 1); 
(gdb) 
17 int agentx_subagent=3D1; /* change this if you want to be a S=
NMP master agent */ 
(gdb) 
30 netsnmp_ds_set_boolean(NETSNMP_DS_APPLICATION_ID, NETSNMP_D=
S_AGENT_ROLE, 1); 
(gdb) 
38 init_agent("example-demon"); 
(gdb) 
 
Breakpoint 2, 0x4002d714 in init_agent () from /usr/lib/libnetsnmpagent=
..so.5 
(gdb)</ul>
 
Now, for those of you still following this, 'init_agent' is resolved in=
libnetsnmpagent.so.
<ul>bld1-dsm> nm -l /vobs/vob3/net-snmp/tfs/x86/agent/.libs/libnetsn=
mpagent.so | grep init_agent 
0000db58 T init_agent /vobs/vob3/net-snmp/src/agent/snmp_vars.c:270<b=
r>
</ul>
What am I missing? Is there an environment variable in gdb I need to se=
t to have it pick up the right shared module? I tried static linking bu=
t I got lost in a maze of link order problems. I would rather get the d=
ynamic debugging going but I am open to static linking if some one coul=
d help with the link order. That is a whole other post though....thanks=
for the help. 
 
Thanks, 
 
Alan L. Anderson 
RadiSys</body></html>=

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