Red Hat ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE, Manual

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Chapter 15.
Examining the Symbol Table
The commands described in this chapter allow you to inquire about the symbols (names of variables,
functions and types) defined in your program. This information is inherent in the text of your program
and does not change as your program executes. gdb finds it in your program’s symbol table, in the
file indicated when you started gdb (refer to Section 4.1.1 Choosing files ), or by one of the file-
management commands (refer to Section 17.1 Commands to specify files ).
Occasionally, you may need to refer to symbols that contain unusual characters, which gdb ordinarily
treats as word delimiters. The most frequent case is in referring to static variables in other source
files (refer to Section 10.2 Program variables ). File names are recorded in object files as debugging
symbols, but gdb would ordinarily parse a typical file name, like
foo.c
, as the three words
foo . c
.
To allow gdb to recognize
foo.c
as a single symbol, enclose it in single quotes; for example,
p ’foo.c’::x
looks up the value of
x
in the scope of the file
foo.c
.
info address
symbol
Describe where the data for
symbol
is stored. For a register variable, this says which register it
is kept in. For a non-register local variable, this prints the stack-frame offset at which the variable
is always stored.
Note the contrast with
print &
symbol
, which does not work at all for a register variable, and
for a stack local variable prints the exact address of the current instantiation of the variable.
info symbol
addr
Print the name of a symbol which is stored at the address
addr
. If no symbol is stored exactly at
addr
, gdb prints the nearest symbol and an offset from it:
(gdb) info symbol 0x54320
_initial 396 in section .text
This is the opposite of the
info address
command. You can use it to find out the name of a
variable or a function given its address.
whatis
expr
Print the data type of expression
expr
.
expr
is not actually evaluated, and any side-effecting
operations (such as assignments or function calls) inside it do not take place. Refer to Section
10.1 Expressions .
whatis
Print the data type of
$
, the last value in the value history.
ptype
typename
Print a description of data type
typename
.
typename
may be the name of a type, or for C code
it may have the form
class
class-name
,
struct
struct-tag
,
union
union-tag
or
enum
enum-tag
.