gdb: tfind
13.2.1 'tfind N'
----------------
The basic command for selecting a trace snapshot from the buffer is
'tfind N', which finds trace snapshot number N, counting from zero. If
no argument N is given, the next snapshot is selected.
Here are the various forms of using the 'tfind' command.
'tfind start'
Find the first snapshot in the buffer. This is a synonym for
'tfind 0' (since 0 is the number of the first snapshot).
'tfind none'
Stop debugging trace snapshots, resume _live_ debugging.
'tfind end'
Same as 'tfind none'.
'tfind'
No argument means find the next trace snapshot or find the first
one if no trace snapshot is selected.
'tfind -'
Find the previous trace snapshot before the current one. This
permits retracing earlier steps.
'tfind tracepoint NUM'
Find the next snapshot associated with tracepoint NUM. Search
proceeds forward from the last examined trace snapshot. If no
argument NUM is given, it means find the next snapshot collected
for the same tracepoint as the current snapshot.
'tfind pc ADDR'
Find the next snapshot associated with the value ADDR of the
program counter. Search proceeds forward from the last examined
trace snapshot. If no argument ADDR is given, it means find the
next snapshot with the same value of PC as the current snapshot.
'tfind outside ADDR1, ADDR2'
Find the next snapshot whose PC is outside the given range of
addresses (exclusive).
'tfind range ADDR1, ADDR2'
Find the next snapshot whose PC is between ADDR1 and ADDR2
(inclusive).
'tfind line [FILE:]N'
Find the next snapshot associated with the source line N. If the
optional argument FILE is given, refer to line N in that source
file. Search proceeds forward from the last examined trace
snapshot. If no argument N is given, it means find the next line
other than the one currently being examined; thus saying 'tfind
line' repeatedly can appear to have the same effect as stepping
from line to line in a _live_ debugging session.
The default arguments for the 'tfind' commands are specifically
designed to make it easy to scan through the trace buffer. For
instance, 'tfind' with no argument selects the next trace snapshot, and
'tfind -' with no argument selects the previous trace snapshot. So, by
giving one 'tfind' command, and then simply hitting <RET> repeatedly you
can examine all the trace snapshots in order. Or, by saying 'tfind -'
and then hitting <RET> repeatedly you can examine the snapshots in
reverse order. The 'tfind line' command with no argument selects the
snapshot for the next source line executed. The 'tfind pc' command with
no argument selects the next snapshot with the same program counter (PC)
as the current frame. The 'tfind tracepoint' command with no argument
selects the next trace snapshot collected by the same tracepoint as the
current one.
In addition to letting you scan through the trace buffer manually,
these commands make it easy to construct GDB scripts that scan through
the trace buffer and print out whatever collected data you are
interested in. Thus, if we want to examine the PC, FP, and SP registers
from each trace frame in the buffer, we can say this:
(gdb) tfind start
(gdb) while ($trace_frame != -1)
> printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
$trace_frame, $pc, $sp, $fp
> tfind
> end
Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
Or, if we want to examine the variable 'X' at each source line in the
buffer:
(gdb) tfind start
(gdb) while ($trace_frame != -1)
> printf "Frame %d, X == %d\n", $trace_frame, X
> tfind line
> end
Frame 0, X = 1
Frame 7, X = 2
Frame 13, X = 255
Info Catalog
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