Debugging with GDB (September 2007)

Chapter 14: HP-UX Configuration-Specific Information 145
Note: To attach and find leaks for PA-32 applications from the startup, the
environment variable RTC_INIT should be set to on in addition to preloading
the librtc.[sl|so] library before starting the application, as follows:
$ LD_PRELOAD=/opt/langtools/lib/librtc.sl RTC_INIT=on <application>
If RTC_INIT is turned on, librtc starts recording heap information for PA32
process, by default. Hence, you must set this environment variable only when
it is required, and you must not export this environment variable for shell.
2. Run the program.
3. Start a debugging session as follows:
gdb -leaks <executable-name> <process-id>
4. Use info heap and info leaks commands to obtain a memory analysis report of
the application.
Note: From HP WDB 5.7 onwards, the archive version of the run time check li-
brary, librtc.a, is not available. You must use the shared version of the library,
librtc.[sl|so], instead.
14.10.7 Configuring memory debugging settings
The following configuration settings are supported to control the level of details of
information required to b e displaye d when debugging memory leaks.
14.10.7.1 Specifying the stack depth
Memory debugging reduces the performance of an application by 20-40% because of
stack unwinding. To provide a clear profile of every allocation in the program, the
debugger collects the stack trace information for every allocation in the debugged ap-
plication. Reducing the stack depth (the number of stack frames that the debugger
collects for each allocation) reduces the performance degradation.
The set heap-check frame-count command enables you to control the depth of the
stack frames that are collected by WDB for each allocation. By default, four stack
frames are displayed from the alloc ating call stack.
To set the depth of the stack frames that is collected by WDB, enter the following
command at the gdb prompt:
$ set heap-check frame-count [num]
The stack depth, [num], is the number of stack frames that WDB collects for each
allocation.
You can specify a higher value for [num] to view more stack frames for each reported
allocation. However, the performance of the application is reduced because of the
increased stack depth.
14.10.7.2 Specifying minimum leak size
WDB enables you to specify the minimum leak size for stack trace collection to improve
the program’s performance.