Debugging with GDB (September 2007)

Chapter 5: Stopping and Continuing 35

tbreak args

Set a breakpoint enabled only for one stop. args are the same as for the break

command, and the breakpoint is set in the same way, but the breakpoint is

automatically deleted after the ﬁrst time your program stops there. See Sec-

tion 5.1.4 [Disabling breakp oints], page 39.

xbreak args

Set breakpoint at procedure exit. Argument may be function name, or "*"

and an address. If a function is speciﬁed, execution breaks at end of co de for

that function. If an address is speciﬁed, execution breaks at the end of the

function that contains the speciﬁed address . When no arguments are speciﬁed,

the current execution address of the selected stack frame is used by default.

This is useful for breaking on return to a stack frame.

hbreak args

Set a hardware-assisted breakpoint. args are the sam e as for the break com-

mand and the breakpoint is set in the same way, but the breakpoint re quires

hardware support and some target hardware may not have this support. The

main purpose of this is EPROM/ROM code debugging, so you can set a break-

point at an instruction without changing the instruction. This can be used

with the new trap-generation provided by SPARClite DSU and some x86-based

targets. These targets will generate traps when a program accesses some data

or instruction address that is assigned to the debug registers. However the

hardware breakpoint registers can take a limited number of breakpoints. For

example, on the DSU, only two data breakpoints c an be set at a time, and GDB

will reject this command if more than two are used. Delete or disable unused

hardware breakpoints before setting new ones (see Section 5.1.4 [Disabling],

page 39). See Section 5.1.5 [Break conditions], page 40.

thbreak args

Set a hardware-assisted breakpoint enabled only for one s top. args are the

same as for the hbreak command and the breakpoint is set in the same way.

However, like the tbreak command, the breakp oint is automatically deleted

after the ﬁrst time your program stops there. Also, like the hbreak command,

the breakpoint requires hardware support and some target hardware may not

have this support. See Section 5.1.4 [Disabling breakpoints], page 39. See also

Section 5.1.5 [Break conditions], page 40.

rbreak regex

Set breakpoints on all functions matching the regular expression regex. This

command sets an unconditional breakpoint on all matches, printing a list of all

breakpoints it set. Once these breakpoints are set, they are treated just like the

breakpoints set with the break com mand. You can delete them, disable them,

or make them conditional the same way as any other breakpoint.

The syntax of the regular expression is the standard one used with tools like

‘grep’. Note that this is diﬀerent from the syntax used by shells, so for instance

foo* matches all functions that include an fo followed by zero or more os. There

is an implicit .* leading and trailing the regular expression you supply, so to

match only functions that be gin with foo, use ^foo.