Frame Apply (Debugging with GDB)

8.5 Applying a Command to Several Frames.

frame apply [all | count | -count | level level…] [option]… command

The frame apply command allows you to apply the named command to one or more frames.

all: Specify all to apply command to all frames.
count: Use count to apply command to the innermost count frames, where count is a positive number.
-count: Use -count to apply command to the outermost count frames, where count is a positive number.
level: Use level to apply command to the set of frames identified by the level list. level is a frame level or a range of frame levels as level1-level2. The frame level is the number shown in the first field of the ‘backtrace’ command output. E.g., ‘2-4 6-8 3’ indicates to apply command for the frames at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.

Note that the frames on which frame apply applies a command are also influenced by the set backtrace settings such as set backtrace past-main and set backtrace limit N. See Backtraces.

The frame apply command also supports a number of options that allow overriding relevant set backtrace settings:

-past-main [on|off]: Whether backtraces should continue past main. Related setting: set backtrace past-main.
-past-entry [on|off]: Whether backtraces should continue past the entry point of a program. Related setting: set backtrace past-entry.

By default, GDB displays some frame information before the output produced by command, and an error raised during the execution of a command will abort frame apply. The following options can be used to fine-tune these behaviors:

-c: The flag -c, which stands for ‘continue’, causes any errors in command to be displayed, and the execution of frame apply then continues.
-s: The flag -s, which stands for ‘silent’, causes any errors or empty output produced by a command to be silently ignored. That is, the execution continues, but the frame information and errors are not printed.
-q: The flag -q (‘quiet’) disables printing the frame information.

The following example shows how the flags -c and -s are working when applying the command p j to all frames, where variable j can only be successfully printed in the outermost #1 main frame.

(gdb) frame apply all p j
#0  some_function (i=5) at fun.c:4
No symbol "j" in current context.
(gdb) frame apply all -c p j
#0  some_function (i=5) at fun.c:4
No symbol "j" in current context.
#1  0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
$1 = 5
(gdb) frame apply all -s p j
#1  0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
$2 = 5
(gdb)

By default, ‘frame apply’, prints the frame location information before the command output:

(gdb) frame apply all p $sp
#0  some_function (i=5) at fun.c:4
$4 = (void *) 0xffffd1e0
#1  0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
$5 = (void *) 0xffffd1f0
(gdb)

If the flag -q is given, no frame information is printed:

(gdb) frame apply all -q p $sp
$12 = (void *) 0xffffd1e0
$13 = (void *) 0xffffd1f0
(gdb)

faas command

Shortcut for frame apply all -s command. Applies command on all frames, ignoring errors and empty output.

It can for example be used to print a local variable or a function argument without knowing the frame where this variable or argument is, using:

(gdb) faas p some_local_var_i_do_not_remember_where_it_is

The faas command accepts the same options as the frame apply command. See frame apply.

Note that the command tfaas command applies command on all frames of all threads. See See Threads.