Red Hat ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE, Руководство пользователя

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Chapter 3. A Sample gdb Session 9
#4 0x79dc in expand_input () at macro.c:40
#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
We step through a few more lines to see what happens. The first two times, we can use
s
; the next two
times we use
n
to avoid falling into the
xstrdup
subroutine.
(gdb) s
0x3b5c 532 if (rquote != def_rquote)
(gdb) s
0x3b80 535 lquote = (lq == nil || *lq == ’\0’) ? \
def_lquote : xstrdup(lq);
(gdb)
n
536 rquote = (rq == nil || *rq == ’\0’) ? def_rquote\
: xstrdup(rq);
(gdb) n
538 len_lquote = strlen(rquote);
The last line displayed looks a little odd; we can examine the variables
lquote
and
rquote
to see
if they are in fact the new left and right quotes we specified. We use the command
p
(
print
) to see
their values.
(gdb) p lquote
$1 = 0x35d40 " QUOTE "
(gdb) p rquote
$2 = 0x35d50 " UNQUOTE "
lquote
and
rquote
are indeed the new left and right quotes. To look at some context, we can display
ten lines of source surrounding the current line with the
l
(
list
) command.
(gdb) l
533 xfree(rquote);
534
535
lquote = (lq == nil || *lq == ’\0’) ? def_lquote\
: xstrdup (lq);
536 rquote = (rq == nil || *rq == ’\0’) ? def_rquote\
: xstrdup (rq);
537
538
len_lquote = strlen(rquote);
539 len_rquote = strlen(lquote);
540 }
541
542
void
Let us step past the two lines that set
len_lquote
and
len_rquote
, and then examine the values of
those variables.
(gdb) n
539 len_rquote = strlen(lquote);
(gdb) n
540 }
(gdb) p len_lquote
$3 = 9