Re: [Caml-list] Bug in caml_string_get16?

[Gabriel Scherer <gabriel.scherer@gmail.com>]

Despite the somewhat unclear reporting (I didn't read the first mail
carefully enough to understand the problem), this is in fact a
report for a very serious bug. I have a fix in the works that should
end upstream quickly.

        OCaml version 4.01.0

# external set64 : string -> int -> int -> unit = "caml_string_set64";;
external set64 : string -> int -> int -> unit = "caml_string_set64"
# set64 "0" 1 42;;
zsh: segmentation fault

On Tue, Nov 5, 2013 at 10:53 AM, Nicolas Trangez <nicolas@incubaid.com> wrote:
> On Tue, 2013-11-05 at 07:54 +0400, Ivan Gotovchits wrote:
>> Nicolas Trangez <nicolas@incubaid.com> writes:
>>
>> > What would you expect to be the output of this code?
>>
>> It should fail :)
>>
>> In a string literal any symbol that you can type with your keyboard is
>> stored in a special encoding called ASCII. With "1" you have just
>> created a string containig a single byte with a value 49. So, first off
>> all, your string is too short, because it has length of 1, when int16
>> obviously needs two bytes of storage space.  If you really interested,
>> binary 1 will be represented in a memory of a little endian computer
>> like this: "\x01\x00". The special escape symbol "\" allows us to type
>> untypable. The the code
>>
>>     open EndianString
>>     let d = LittleEndian.get_int16 "\x01\x00" 0
>>
>> will yield:
>>
>>     val d : int = 1
>>
>> By the way, if we try your string (with a more correct invocation):
>>
>>     open EndianString
>>     let d = LittleEndian.get_int8 "1" 0
>>
>> we will got:
>>
>>     val d : int = 49
>>
>> Futher reading:
>>
>> 1. man ascii
>> 2. wikipedia article on endianess
>
> Oh, don't be mistaken. The question was rhetorical, in order to report a
> bug (or get told it's not a bug at all) & provide a test-case :-)
> I'm well aware of all of the above ;-)
>
> Thanks!
>
> Nicolas
>
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs