gdb - customize it the way <b>you</b> want

gdb allows creating gdb-scoped variables "on the fly":
```
set $foo = 2 * i
```
To see the list of defined convenience variables:
```
 show convenience
```
To initialize a convenience variable only if it's not yet defined:
```
init-if-undefined $foo = 2 * i
```
Convenience variables are useful when writing gdb macros - we'll get to this later...

Originally written by