5.2. Command completion
gdb can fill in the rest of a word in a command for you, if there is
only one possibility; it can also show you what the valid possibilities
are for the next word in a command, at any time. This works for gdb
commands, gdb subcommands, and the names of symbols in your program.
Press the [TAB] key whenever you want gdb to fill out the rest
of a word. If there is only one possibility, gdb fills in the
word, and waits for you to finish the command (or press [RET] to
enter it). For example, if you type
gdb fills in the rest of the word breakpoints, since that is
the only info subcommand beginning with bre:
You can either press [RET] at this point, to run the info
breakpoints command, or backspace and enter something else, if
breakpoints does not look like the command you expected. (If you
were sure you wanted info breakpoints in the first place, you
might as well just type [RET] immediately after info bre,
to exploit command abbreviations rather than command completion).
If there is more than one possibility for the next word when you press
[TAB], gdb sounds a bell. You can either supply more
characters and try again, or just press [TAB] a second time;
gdb displays all the possible completions for that word. For
example, you might want to set a breakpoint on a subroutine whose name
begins with make_, but when you type b make_[TAB] gdb
just sounds the bell. Typing [TAB] again displays all the
function names in your program that begin with those characters, for
example:
(gdb) b make_ [TAB]
gdb sounds bell; press [TAB] again, to see: make_a_section_from_file make_environ
make_abs_section make_function_type
make_blockvector make_pointer_type
make_cleanup make_reference_type
make_command make_symbol_completion_list
(gdb) b make_ |
After displaying the available possibilities, gdb copies your
partial input (b make_ in the example) so you can finish the
command.
If you just want to see the list of alternatives in the first place, you
can press M-? rather than pressing [TAB] twice. M-?
means [META] ?. You can type this either by holding down a
key designated as the [META] shift on your keyboard (if there is
one) while typing ?, or as [ESC] followed by ?.
Sometimes the string you need, while logically a "word", may contain
parentheses or other characters that gdb normally excludes from
its notion of a word. To permit word completion to work in this
situation, you may enclose words in ' (single quote marks) in
gdb commands.
The most likely situation where you might need this is in typing the
name of a C++ function. This is because C++ allows function
overloading (multiple definitions of the same function, distinguished
by argument type). For example, when you want to set a breakpoint you
may need to distinguish whether you mean the version of name
that takes an int parameter, name(int), or the version
that takes a float parameter, name(float). To use the
word-completion facilities in this situation, type a single quote
' at the beginning of the function name. This alerts
gdb that it may need to consider more information than usual
when you press [TAB] or M-? to request word completion:
(gdb) b 'bubble( M-?
bubble(double,double) bubble(int,int)
(gdb) b 'bubble( |
In some cases, gdb can tell that completing a name requires using
quotes. When this happens, gdb inserts the quote for you (while
completing as much as it can) if you do not type the quote in the first
place:
(gdb) b bub [TAB]
gdb alters your input line to the following, and rings a bell: (gdb) b 'bubble( |
In general, gdb can tell that a quote is needed (and inserts it) if
you have not yet started typing the argument list when you ask for
completion on an overloaded symbol.
For more information about overloaded functions, refer to Section 14.4.1.3 C++expressions. You can use the command set
overload-resolution off to disable overload resolution;
refer to Section 14.4.1.7 gdb features for C++.
