A breakpoint makes your program stop whenever a certain point in
the program is reached. For each breakpoint, you can add
conditions to control in finer detail whether your program stops.
You can set breakpoints with the
break command and its variants
(see section Setting breakpoints), to specify the place where
your program should stop by line number, function name or exact address
in the program.
In languages with exception handling (such as GNU C++), you can also set
breakpoints where an exception is raised (see section Breakpoints and exceptions).
In SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can now set breakpoints in shared libraries before the executable is run.
A watchpoint is a special breakpoint that stops your program when the value of an expression changes. You must use a different command to set watchpoints (see section Setting watchpoints), but aside from that, you can manage a watchpoint like any other breakpoint: you enable, disable, and delete both breakpoints and watchpoints using the same commands.
You can arrange to have values from your program displayed automatically whenever GDB stops at a breakpoint. See section Automatic display.
GDB assigns a number to each breakpoint or watchpoint when you create it; these numbers are successive integers starting with one. In many of the commands for controlling various features of breakpoints you use the breakpoint number to say which breakpoint you want to change. Each breakpoint may be enabled or disabled; if disabled, it has no effect on your program until you enable it again.
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