Re: Splitting strings into arrays with sscanf

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: Splitting strings into arrays with sscanf
Date	2017-06-16 12:31 -0700
Organization	None to speak of
Message-ID	<lntw3fafv5.fsf@kst-u.example.com> (permalink)
References	<oi14f9$edg$3@dont-email.me> <oi15e9$g8h$1@dont-email.me> <F1V0B.2767$AG1.2130@fx42.iad>

Show all headers | View raw

scott@slp53.sl.home (Scott Lurndal) writes:
> Lew Pitcher <lew.pitcher@digitalfreehold.ca> writes:
[...]
>>Line 7 looks to be...
>>  char data[10][4] = "";
>>which describes an array of 10 elements, each containing an array of 4 
>>characters. However, your initialization only consists of a single array of 
>>1 character (a \0).
>>
>>Apparently, tcc is expecting an initialization that looks something like
>>  char data[10][4] = {"","","","","","","","","",""};

It also accepts
    char data[10][4] = {""};
or
    char data[10][4] = { 0 };
The latter is a valid initializer for an object of any type.

>  As "" is of type 'char *', the values assigned to the array will likely
> not be as expected (i.e. either the high-byte (big-endian systems) or the
> low-byte (little-endian systems) of the address to the empty string will
> be stored in data, rather than the expected single NUL byte at column 0
> of each of the ten rows).

No, "" is of type char[1].  Like any array expression, it's implicitly
converted to a pointer expression in most contexts, but a string literal
in an initializer used to initialize an array object is one of the three
explicitly listed exceptions.  Using a string literal to initialize an
array of char is perfectly valid, and tcc handles it correctly as far as
I can tell.

>  Technically, the correct initializer looks more like:
>
>   char data[10][4] = {
>     { 0, 1, 2, 3 },   /* row 0 */
>     { 4, 5, 6, 7 },   /* row 1 */
>      ...
>     { 36, 37, 38, 39 }, /* row 9 */
>   };
>
> or
>   char data[10][4] = {
>     { 'a', 'b', 'c', 'd', },  /* row 0 */
>     ...
>     { 'A', 'B', 'C', 'D', },  /* row 9 */
>   };  

That's completely unnecessary.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

Splitting strings into arrays with sscanf DFS <nospam@dfs.com> - 2017-06-16 13:33 -0400
  Re: Splitting strings into arrays with sscanf scott@slp53.sl.home (Scott Lurndal) - 2017-06-16 17:46 +0000
    Re: Splitting strings into arrays with sscanf DFS <nospam@dfs.com> - 2017-06-16 14:02 -0400
      Re: Splitting strings into arrays with sscanf scott@slp53.sl.home (Scott Lurndal) - 2017-06-16 18:15 +0000
        Re: Splitting strings into arrays with sscanf Keith Thompson <kst-u@mib.org> - 2017-06-16 12:28 -0700
    Re: Splitting strings into arrays with sscanf Keith Thompson <kst-u@mib.org> - 2017-06-16 12:20 -0700
  Re: Splitting strings into arrays with sscanf Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-06-16 13:47 -0400
    Re: Splitting strings into arrays with sscanf scott@slp53.sl.home (Scott Lurndal) - 2017-06-16 18:01 +0000
      Re: Splitting strings into arrays with sscanf Barry Schwarz <schwarzb@dqel.com> - 2017-06-16 12:03 -0700
        Re: Splitting strings into arrays with sscanf "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-16 15:33 -0400
          Re: Splitting strings into arrays with sscanf Keith Thompson <kst-u@mib.org> - 2017-06-16 13:16 -0700
      Re: Splitting strings into arrays with sscanf Keith Thompson <kst-u@mib.org> - 2017-06-16 12:31 -0700
      Re: Splitting strings into arrays with sscanf "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-16 15:45 -0400
  Re: Splitting strings into arrays with sscanf "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-16 14:07 -0400
  Re: Splitting strings into arrays with sscanf "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-16 14:22 -0400
    Re: Splitting strings into arrays with sscanf DFS <nospam@dfs.com> - 2017-06-16 15:36 -0400
      Re: Splitting strings into arrays with sscanf "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-16 17:17 -0400
  Re: Splitting strings into arrays with sscanf Barry Schwarz <schwarzb@dqel.com> - 2017-06-16 12:06 -0700
  Re: Splitting strings into arrays with sscanf Real Troll <Real.Troll@Trolls.com> - 2017-06-16 17:30 -0400
  Re: Splitting strings into arrays with sscanf ike@iceland.freeshell.org - 2017-06-17 16:49 +0000
  Re: Splitting strings into arrays with sscanf Richard Damon <Richard@Damon-Family.org> - 2017-06-17 18:25 -0400

csiph-web