In fact, delete n deletes the breakpoint with identifier n. Hopefully, GDB is still open from the previous subsection, so check it out: Note that hardware-assisted watchpoints that were set before setting can-use-hw-watchpoints to zero will still use the hardware mechanism of watching expression values.
But this may still be worth it, to catch errors where you have no clue what part of your program is the culprit.
Finally, enable breakpoint 2 and rerun the program. In multi-threaded programs, watchpoints will detect changes to the watched expression from every thread.
Also, you may wish to see the symbolic form only if the address being printed is reasonably close to the closest earlier symbol: For a pending breakpoint, the original string passed to the breakpoint command will be listed as it cannot be resolved until the appropriate shared library is loaded in the future.
For example, this is what a stack frame display looks like with set print address on: You can hit CTRL-C and that'll stop the program wherever it happens to be and return you to a " gdb " prompt. Multiple functions in the program may have the same name. Breakpoint 3, main at main. Attach to a Running Process If your program is already going and you want to stop it and debug, first you'll need the process ID PIDwhich will be a number.
This setting does not affect any pending breakpoints previously created. The default is off. Just as you can set breakpoints, you can also remove them.
However the hardware breakpoint registers can take a limited number of breakpoints. Hardware watchpoints execute very quickly, and the debugger reports a change in value at the exact instruction where the change occurs. Additionally, the tui reg allows control of the register window, and will open it if it's not already open.
Stepping Around Once execution stops at a breakpoint, you can tell the debugger to do a few things. Another situation where it is helpful to show symbol filenames and line numbers is when disassembling code; GDB shows you the line number and source file that corresponds to each instruction.
This logic works for breakpoints with multiple locations, too. There are several ways to start the debugger e. Note that watchpoints restricted to a single thread in this way only work with Hardware Watchpoints.
You can enable or disable breakpoints using the enable and disable commands which take an argument of the breakpoint identifier for the breakpoint you want to enable or disable.
Depending on your system, watchpoints may be implemented in software or hardware. GDB refuses to create a watchpoint that watches a never-changing value: See section Disabling breakpoints. In this case, GDB will evaluate expr, take the address of the result, and watch the memory at that address.
No such file or directory. By filename and line number. See the next section for how to use these other windows. For some targets, GDB can automatically decide if hardware or software breakpoints should be used, depending on whether the breakpoint address is read-only or read-write.
This applies to breakpoints set with the break command as well as to internal breakpoints set by commands like next and finish. # gdb [core dump] Start GDB (with optional core dump). be debugged. run Run the program to be debugged. kill Kill the running program.
Breakpoints break Set a new breakpoint. delete Remove a breakpoint. clear Delete all breakpoints. x/nfu address> Print memory. n: How many units to print (default. Stopping and Continuing. break *address Set a breakpoint at address address.
You can use this to set breakpoints in parts of your program which do not have debugging information or source files.
break (gdb) break frik.c thread 28 if bartab > lim. (using gdb's break command) Breakpoint 1 was set using break Cannot insert breakpoint 2. Cannot access memory at address 0x (gdb) info b Num Type Disp Enb Address What 1 breakpoint keep y 0x 2 breakpoint keep y 0x This depends on the languages used to write your program.
GDB will break when the expression expr is written into by the program and its value changes. The simplest (and the most popular) use of this command is to watch the value of a single variable: The simplest (and the most popular) use of this command is to watch the value of a single variable.
watch only breaks on write, rwatch let you break on read, and awatch let you break on read/write. You can set read watchpoints on memory locations: gdb$ rwatch *0xfeedface Hardware read watchpoint 2: *0xfeedface but one limitation applies to the rwatch and awatch commands; you can't use gdb .Gdb break write address