sbekman 01/07/07 09:24:34
Modified: pod modperl_dev.pod
Log:
document the trick of setting the breakpoint in the mod_perl code when it's loaded
via DSO
Revision Changes Path
1.28 +47 -0 modperl-2.0/pod/modperl_dev.pod
Index: modperl_dev.pod
===================================================================
RCS file: /home/cvs/modperl-2.0/pod/modperl_dev.pod,v
retrieving revision 1.27
retrieving revision 1.28
diff -u -r1.27 -r1.28
--- modperl_dev.pod 2001/06/29 07:46:02 1.27
+++ modperl_dev.pod 2001/07/07 16:24:33 1.28
@@ -475,6 +475,53 @@
PerlOptions -Authen -Authz -Access
</VirtualHost>
+=head1 Debug notes
+
+=head2 Setting gdb breakpoints with mod_perl built as DSO
+
+If mod_perl is built as a DSO module, you cannot set the breakpoint in
+the mod_perl source files when the I<httpd> program gets loaded into
+the debugger. The reason is simple: At this moment I<httpd> has no
+idea about mod_perl module yet. After the configuration file is
+processed and the mod_perl DSO module is loaded then the breakpoints
+in the source of mod_perl itself can be set.
+
+The trick is to break at I<apr_dso_load>, let it load
+I<libmodperl.so>, then you can set breakpoints anywhere in the modperl
+code:
+
+ % gdb httpd
+ (gdb) b apr_dso_load
+ (gdb) run -DONE_PROCESS
+ [New Thread 1024 (LWP 1600)]
+ [Switching to Thread 1024 (LWP 1600)]
+
+ Breakpoint 1, apr_dso_load (res_handle=0xbfffb48c, path=0x811adcc
+ "/home/stas/apache.org/modperl-perlmodule/src/modules/perl/libmodperl.so",
+ pool=0x80e1a3c) at dso.c:138
+ 141 void *os_handle = dlopen(path, RTLD_NOW | RTLD_GLOBAL);
+ (gdb) finish
+ ...
+ Value returned is $1 = 0
+ (gdb) b modperl_hook_init
+ (gdb) continue
+
+This example shows how to set a breakpoint at I<modperl_hook_init>.
+
+To automate things you can put those in the I<.gdb-jump-to-init> file:
+
+ b apr_dso_load
+ run -DONE_PROCESS -d /home/stas/apache.org/modperl-perlmodule/t \
+ -f /home/stas/apache.org/modperl-perlmodule/t/conf/httpd.conf
+ finish
+ b modperl_hook_init
+ continue
+
+and then start the debugger with:
+
+ % gdb /home/stas/httpd-2.0/bin/httpd -command \
+ /home/stas/apache.org/modperl-perlmodule/t/.gdb-jump-to-init
+
=head1 Notes for Developers
