gdb-show-changed-values

gdb-show-changed-values is a variable defined in `gdb-mi.el'.
Its value is

t

Documentation:
If non-nil change the face of out of scope variables and changed values.
Out of scope variables are suppressed with `shadow' face.
Changed values are highlighted with the face `font-lock-warning-face'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.