the code below will compile in visual c++ 2003, but im not sure its
valid.
unsigned char myString[200] = "";
after this line executes, all the bytes within myString are indeed set
to '0's' but is this really valid c++ or c? where can I find out how
this is implemented?
Im concerned because I had a 3rd party library wrapper which was
crashing, and I was able to alleviate the crash by changing the
initialization method from the above to ...
unsigned char myString[200];
memset( myString, 0, sizeof( myString ) );
any guidance is greatly appreciated!
-Velik
Oct 24 '08
24  2200 
blargg wrote:
In article
<79************ *************** *******@y29g200 0hsf.googlegrou ps.com>, James
Kanze <ja*********@gm ail.comwrote:
>On Oct 24, 10:46=A0pm, Pete Becker <p...@versatile coding.com>
wrote:
>>On 2008-10-24 16:18:56 -0400, Victor Bazarov
<v.Abaza...@c omAcast.netsaid :
8.5.1/7:
<<If there are fewer initializers in the list than there are members in
the aggregate, then each member not
explicitly initialized shall be value-initialized (8.5).>>
Well, yes, that's the requirement for aggregate
initializatio n. But does aggregate initialization apply here?
Aggregate initialization is indicated by "a brace-enclosed,
comma-separated list ...", which isn't present here. I don't
see anything in 8.5.2 [dcl.init.string] that says that
aggregate initialization is used, although the "optionally
enclosed in braces" hints that it may be.
Well, I rather think it was intended, although you do have a
point. Probably a defect in the standard. (Maybe I should
raise an issue. I'd love to say that it was just editorial, and
just push it off on you, but I think it's a little too much for
that.)
If it's not required, then the following would result in a[2] and a[3]
having const indeterminate values, a rather odd situation:
char const a [4] = "X";
Not sure about the "odd" comment. The compiler that is created
following the rule that it's allowed to forgo the initialisation of the
array elements beyond the terminating null char, would probably *warn*
about the unintialised const and force using the curly brackets form:
char const a [4] = { 'X' };
which ensures that the tail is value-initialised.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
On Oct 24, 11:46*pm, Pete Becker <p...@versatile coding.comwrote :
On 2008-10-24 17:17:10 -0400, "Default User" <defaultuse...@ yahoo.comsaid:
Pete Becker wrote:
On 2008-10-24 16:29:45 -0400, "Default User"
<defaultuse...@ yahoo.comsaid:
>C89's wording was similar to the C++ standard, but had
further examples to show that initialization with a string
literal is identical to a brace-enclosed list of the
characters, which would amount to the same thing.
So C99 made it crystal clear, presumably because C90 wasn't. <g>
It was, I think, clear enough. It just wasn't all put
together nicely. They had examples to show that:
* *char str[] = "XYZ";
Was equivalent to:
* *char str[] = {'X', 'Y', 'Z', '\0'};
So if a string literal is equivalent to a brace-enclosed
list of characters, then the "fewer initializer" rule would
come into play to finish out an array larger than the string
literal with '\0'.
Examples in standards are not normative. That is, they do not
impose requirements. They illustrate what the words say. If
the words don't say it, examples don't make it true.
In this case, the words do say what the example shows. But it
has nothing to do with the case at hand, something like:
char str[ 20 ] = "abc" ;
Is this guaranteed to initialize all 20 bytes, or just the first
four?
--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
On 2008-10-24 19:21:26 -0400, "Default User" <de***********@ yahoo.comsaid:
>
Searching back in comp.std.c, I find that apparently this issue was
submitted as a Defect Report / Technical Corrigendum that "clarifies
that a string literal is equivalent to a brace-enclosed
list of characters."
So the issue has come up before there, and that report is probably why
C99 explicitly said so.
Sigh. That's what I said several messages back. C99 changed the wording
because the C90 words weren't clear.
--
Pete
Roundhouse Consulting, Ltd. ( www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
( www.petebecker.com/tr1book)
Pete Becker wrote:
On 2008-10-24 19:21:26 -0400, "Default User"
<de***********@ yahoo.comsaid:
Searching back in comp.std.c, I find that apparently this issue was
submitted as a Defect Report / Technical Corrigendum that "clarifies
that a string literal is equivalent to a brace-enclosed
list of characters."
So the issue has come up before there, and that report is probably
why C99 explicitly said so.
Sigh. That's what I said several messages back. C99 changed the
wording because the C90 words weren't clear.
You mentioned nothing about this defect report. My research was to add
to the previous discussion, not to refute anything.
Brian
--
If televison's a babysitter, the Internet is a drunk librarian who
won't shut up.
-- Dorothy Gambrell ( http://catandgirl.com)
On Oct 24, 10:47*pm, Pete Becker <p...@versatile coding.comwrote :
On 2008-10-24 17:11:10 -0400, James Kanze <james.ka...@gm ail.comsaid:
On Oct 24, 10:46*pm, Pete Becker <p...@versatile coding.com>
wrote:
On 2008-10-24 16:18:56 -0400, Victor Bazarov
<v.Abaza...@com Acast.netsaid:
8.5.1/7:
<<If there are fewer initializers in the list than there are members in
the aggregate, then each member not
explicitly initialized shall be value-initialized (8.5).>>
Well, yes, that's the requirement for aggregate
initialization. But does aggregate initialization apply
here? Aggregate initialization is indicated by "a
brace-enclosed, comma-separated list ...", which isn't
present here. I don't see anything in 8.5.2
[dcl.init.string] that says that aggregate initialization
is used, although the "optionally enclosed in braces" hints
that it may be.
Well, I rather think it was intended, although you do have a
point. *Probably a defect in the standard. *(Maybe I should
raise an issue. *I'd love to say that it was just editorial,
and just push it off on you, but I think it's a little too
much for that.)
Me, too. <g>
Done. I've raised the issue with the committee.
--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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