[Bug cli/24124] Command `b *804874e` sets breakpoint at 0xc480a - hex value of 804874

["tromey at sourceware dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=24124

--- Comment #3 from Tom Tromey <tromey at sourceware dot org> ---
(In reply to Enze Li from comment #2)

> "804874e" is parsed as a floating point number because "en" stands for
> "10^n".  If there is no decimal number after "e", "e" will be ignored.  "d"
> and "f" are not as special as "e", that is why breakpoint address with a "d"
> or "f" are recognized as illegal.  This is my understanding.

I think gdb's lexing here is weird, because it disagrees with C:

prentzel. gcc --syntax-only q.c
q.c:1:11: error: exponent has no digits
    1 | float x = 80e;
      |           ^~~

(gdb) print 80e
$1 = 80
(gdb) ptype 80e
type = double

So not treating this as floating point (and rejecting the parse)
might be fine.

> In GDB, do users usually use decimal numbers to define the address of
> breakpoints?

No but nothing prohibits it.

> Or, if only hexadecimal numbers are used to set the breakpoint
> address, how about we restrict the value of the address to start with 0x?

That's harder than it sounds because the text after the "*" is an
arbitrary expression, not just an integer.

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