gdb.info: Completion

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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) info bre <TAB>
GDB fills in the rest of the word `breakpoints', since that is the only
`info' subcommand beginning with `bre':
     (gdb) info breakpoints
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, see *Note C++
expressions: C plus plus expressions.  You can use the command `set
overload-resolution off' to disable overload resolution; see *Note GDB
features for C++: Debugging C plus plus.