OK, I think I misunderstood Paul's command line "M-x gud-gdb RET
bootstrap-emacs RET" as meaning that after executing "M-x gud-gdb RET" the
only thing that should appear after the prompt is "bootstrap-emacs", so I
deleted the "gdb --full-name" prefix that appeared there automatically. If
I keep this prefix, the error reported above doesn't occur. However, now I
get the following complaint from gdb:

> No executable file specified.
> Use the "file" or "exec-file" command.

Here's the complete contents of the *gud* buffer.

Current directory is ~/
GNU gdb (GDB) 8.0
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin16.6.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
bootstrap-emacs: No such file or directory.
(gdb) b main
No symbol table is loaded.  Use the "file" command.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (main) pending.
(gdb) r
Starting program:
No executable file specified.
Use the "file" or "exec-file" command.

On Fri, Aug 11, 2017 at 12:59 PM, Itai Berli <itai.berli@gmail.com> wrote:

> By the way, the *gud* buffer's first line is
>
> > Current directory is ~/
>
> However, the Emacs source code is in ~/emacs. Maybe this is the problem?
> But I started Emacs from ~/emacs. How can I set the *gud* buffer's current
> directory?
>
> On Fri, Aug 11, 2017 at 12:55 PM, Itai Berli <itai.berli@gmail.com> wrote:
>
>> Typing "b main<RET>" in the *gud* buffer results in the following error
>> message:
>>
>> > Current buffer has no process
>>
>> On Fri, Aug 11, 2017 at 12:52 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>>
>>> > From: Itai Berli <itai.berli@gmail.com>
>>> > Date: Fri, 11 Aug 2017 12:27:01 +0300
>>> > Cc: Emacs developers <emacs-devel@gnu.org>
>>> >
>>> > Paul Eggert wrote:
>>> >
>>> > > type the GDB command "b Fexpand_file_name" to plant a breakpoint in
>>> (say) Fexpand_file_name
>>> >
>>> > What do you mean by 'Fexpand_file_name'? The name of a file, or the
>>> name of a function?
>>>
>>> It's the name of a function.
>>>
>>> > Could you give me
>>> > a concrete example? Suppose, for instance, I wish to place a
>>> breakpoint at the start of the 'main; function. How
>>> > can I do so?
>>>
>>> "b main".  "b" is a short for "break".
>>>
>>
>>
>