Differences between version 15 and predecessor to the previous major change of DeBugging.
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| Newer page: | version 15 | Last edited on Thursday, June 3, 2004 11:45:19 pm | by MattBrown | Revert |
| Older page: | version 13 | Last edited on Thursday, May 6, 2004 1:29:18 am | by StuartYeates | Revert |
@@ -23,12 +23,13 @@
!!useful gdb(1) commands:
;bt full: give a complete backtrace of a program. If a program crashes __this__ is what the programmer will want from you.
;print: This lets you print out various expressions, eg: "print node" "print *node" "print node->key" "print node->next->key" etc.
-;break: This lets you set breakpoints at functions or lines in the source code, eg: "break main" or "break sourcefile.cpp:55"
-;run: run a program up until a break point.
-;step: step over
a function call
-;next: step into
a function call
+;break: This lets you set breakpoints at functions or lines in the source code, eg: "break main" or "break sourcefile.cpp:55". This can be abbreviated as just "b".
+;run: run a program up until it encounters
a break point or completes.
+;cont: start running from the current command until the next break point or the end
.
+;step: step to the next command, or into
a function call (ie go to the instructions within that function).
+;next: step to the next command, or over
a function call (ie treat the call as a single command)
;frame: change which frame you are working on. eg: "frame 1" will change the scope to frame 1.
!!Other useful debugging tricks and traps:
!strace
@@ -45,8 +46,14 @@
!Core files
To allow crashing programs to create [CoreDump]s you have to remove the ulimit(1) on them. This can be done with the command:
ulimit -c unlimited
Note, this is for the shell (and all its children) only.
+
+By default core files are placed in the working directory (often the same directory the executable is in). This may not be ideal for you if the executable is on a read only file system. To change this behaviour you can use the following command.
+
+ echo /var/cores/core.%e.%p >/proc/sys/kernel/core_pattern
+
+%e is replaced by the executable name and %p is replaced by the pid of the process. For more possible replacements see fs/exec.c in your nearest kernel source.
gdb(1) can also do postmortem analysis on core files like so:
gdb ./''program'' ./''corefile''
