Array Initialization warnings

Array Initialization warnings

[David Stroupe]

When I compile this line of code

int JPEG_MRK_NTSC[4][4] =
{
0x01, 0x02, 0x03, 0x04,
0x05, 0x06, 0x07, 0x08,
0x09, 0x0a, 0x0b, 0x0c,
0x0d, 0x0e, 0x0f, 0x00
};

 with the -Wall option, I get the following warnings

vis.c:264: warning: missing braces around initializer
vis.c:264: warning: (near initialization for `JPEG_MRK_NTSC[0]')

If I look at the values of the array members during execution, they are 
correct.

Is this array really being initialized correctly?
Are the warnings correct?

Is there a way to 'turn off' these particular warnings with a compiler 
directive?

TIA

-- 
Best regards,
David Stroupe
Keyed-Up Software

Re: Array Initialization warnings

[bjorn rohde jensen]

Hi David,

 The compiler is quite right, your initialiser is for
an int JPEG_MRK_NTSC[16].

Try something like;

int JPEG_MRK_NTSC[4][4] =
 {
 {0x01, 0x02, 0x03, 0x04},
 {0x05, 0x06, 0x07, 0x08},
 {0x09, 0x0a, 0x0b, 0x0c},
 {0x0d, 0x0e, 0x0f, 0x00}
 };

yours sincerely,

bjorn

David Stroupe wrote:
> 
> When I compile this line of code
> 
> int JPEG_MRK_NTSC[4][4] =
> {
> 0x01, 0x02, 0x03, 0x04,
> 0x05, 0x06, 0x07, 0x08,
> 0x09, 0x0a, 0x0b, 0x0c,
> 0x0d, 0x0e, 0x0f, 0x00
> };
> 
>  with the -Wall option, I get the following warnings
> 
> vis.c:264: warning: missing braces around initializer
> vis.c:264: warning: (near initialization for `JPEG_MRK_NTSC[0]')
> 
> If I look at the values of the array members during execution, they are
> correct.
> 
> Is this array really being initialized correctly?
> Are the warnings correct?
> 
> Is there a way to 'turn off' these particular warnings with a compiler
> directive?
> 
> TIA
> 
> --
> Best regards,
> David Stroupe
> Keyed-Up Software

Re: Array Initialization warnings

[bjorn rohde jensen]

Hi Sebastian,

 The real issue was the syntax of static initialisation
of multidimentional arrays, we just got a little side tracked.

Bjorn

Sebastian Huber wrote:
> 
> Hello,
> I think this identity between the dereference operator (is this the English
> translation?) and access via pointers is helpful:
> 
> T a [S_1][S_2]...[S_N];
> 
> a [i_1][i_2]...[i_n] <=> a
>         + i_1 * S_2 * ... * S_N_MINUS_1
>         + i_2 * S_3 * ... * S_N_MINUS_1
>         + ... +
>         + i_n
> 
> For example:
> 
> #include <iostream>
> 
> int main()
> {
>         int a [2][2][2][2] = {
>                 { { { 0, 1 }, { 2, 3} }, { { 4, 5 }, { 6, 7 } } },
>                 { { { 8, 9 }, { 10, 11} }, { { 12, 13 }, { 14, 15 } } }
>         };
>         for (int i = 0; i < 16; ++i) {
>                 cout << *(reinterpret_cast<int*>( a) + i) << endl;
>         }
>         std::cout << a [1][0][1][0]
>                 << " == "
>                 << *(reinterpret_cast<int*>( a) + 1 * 2 * 2 * 2 + 0 * 2 * 2 + 1 * 2 + 0)
>                 << endl;
>         return 0;
> }
> 
> Ciao Sebastian

Re: Array Initialization warnings

[Sebastian Huber]

Hello,
I think this identity between the dereference operator (is this the English 
translation?) and access via pointers is helpful:

T a [S_1][S_2]...[S_N];

a [i_1][i_2]...[i_n] <=> a
	+ i_1 * S_2 * ... * S_N_MINUS_1
	+ i_2 * S_3 * ... * S_N_MINUS_1
	+ ... +
	+ i_n

For example:

#include <iostream>

int main()
{
	int a [2][2][2][2] = {
		{ { { 0, 1 }, { 2, 3} }, { { 4, 5 }, { 6, 7 } } },
		{ { { 8, 9 }, { 10, 11} }, { { 12, 13 }, { 14, 15 } } }
	};
	for (int i = 0; i < 16; ++i) {
		cout << *(reinterpret_cast<int*>( a) + i) << endl;
	}
	std::cout << a [1][0][1][0]
		<< " == "
		<< *(reinterpret_cast<int*>( a) + 1 * 2 * 2 * 2 + 0 * 2 * 2 + 1 * 2 + 0)
		<< endl;
	return 0;
}

Ciao Sebastian

On Saturday 20 April 2002 16:03, you wrote:
> Hi guys,
>
> Michal Liptak wrote:
> > I think the internal representation of int[4][4] is the same as int[16]
> > m.
>
>  That is usually the case, i would think, but i am not sure, it
> is required by the standard, so i would not rely on that.
>
> bjorn

Re: Array Initialization warnings

[Oliver Kullmann]

> Hi David,
>
> > Just to clarify...the standard requires the brackets be placed as in
> > your example? If so, guess I had best get to bracketing my arrays.
> >
> It is pretty much up to you, how you handle your arrays. You can
> certainly use multi dimentional arrays and initialise them as such,
> or you could use one dimentional arrays and initialise them as such.
> There is nothing wrong with interpreting an x dimentional array as an
> y dimentional array, i am just saying, that you ought to be consistent.
> Your original code depended on a particular physical layout of the
> array. I am not sure, that physical layout is required by the standard.
>
> >I really did not want to have to go back and recode my array that looks
> >like this:BYTE SUBIMG_NTSC[2][2][4][3][8] = {...
>
> You might want to wait with a rewrite, until someone makes
> a stronger statement about this;)
>
> Yours sincerely,

> bjorn

Hi,

I copied a paragraph from the standard (ISO/IEC 14882:1998(E)):

When initializing a multi-dimensional array, the initializers 
initialize the elements with the last (rightmost) index of the array 
varying the fastest (8.3.4). 

[Example: int x[2][2] = { 3, 1, 4, 2 };
initializes x[0][0] to 3, x[0][1] to 1, x[1][0] to 4, and x[1][1] to 2. 
On the other hand, 
float y[4][3] = { { 1 }, { 2 }, { 3 }, { 4 } }; 
initializes the first column of y (regarded as a two-dimensional array) and 
leaves the rest zero. ]

(paragraph 8.5.1)

Oliver

Re: Array Initialization warnings

[bjorn rohde jensen]

Hi David,

> Just to clarify...the standard requires the brackets be placed as in
> your example? If so, guess I had best get to bracketing my arrays.
> 
It is pretty much up to you, how you handle your arrays. You can
certainly use multi dimentional arrays and initialise them as such,
or you could use one dimentional arrays and initialise them as such.
There is nothing wrong with interpreting an x dimentional array as an
y dimentional array, i am just saying, that you ought to be consistent.
Your original code depended on a particular physical layout of the
array. I am not sure, that physical layout is required by the standard.

>I really did not want to have to go back and recode my array that looks 
>like this:BYTE SUBIMG_NTSC[2][2][4][3][8] = {...

You might want to wait with a rewrite, until someone makes
a stronger statement about this;)

Yours sincerely,

bjorn

RE: Array Initialization warnings

[David Stroupe]

  Hi guys,

Michal Liptak wrote:
 >
 > I think the internal representation of int[4][4] is the same as int[16]
 > m.
 >

That is usually the case, i would think, but i am not sure, it
is required by the standard, so i would not rely on that.

Just to clarify...the standard requires the brackets be placed as in 
your example? If so, guess I had best get to bracketing my arrays.

I really did not want to have to go back and recode my array that looks 
like this:
BYTE SUBIMG_NTSC[2][2][4][3][8] = {...

Thanks to all for the info!!

Re: Array Initialization warnings

[bjorn rohde jensen]

Hi guys,

Michal Liptak wrote:
> 
> I think the internal representation of int[4][4] is the same as int[16]
> m.
> 

 That is usually the case, i would think, but i am not sure, it
is required by the standard, so i would not rely on that.

bjorn

Re: Array Initialization warnings

[Michal Liptak]

I think the internal representation of int[4][4] is the same as int[16]
m.

On Sat, 20 Apr 2002 08:56:22 -0500
"David Stroupe" <dstroupe@keyed-upsoftware.com> wrote:

> >Hi David,
> >
> > The compiler is quite right, your initialiser is for
> >an int JPEG_MRK_NTSC[16].
> >
> >Try something like;
> >
> >int JPEG_MRK_NTSC[4][4] =
> > {
> > {0x01, 0x02, 0x03, 0x04},
> > {0x05, 0x06, 0x07, 0x08},
> > {0x09, 0x0a, 0x0b, 0x0c},
> > {0x0d, 0x0e, 0x0f, 0x00}
> > };
> >
> >yours sincerely,
> >
> >bjorn
> 
> Thanks bjorn, indeed that eliminates the warnings and your explanation makes perfect sense.  Is it an accident...or just lucky,
> that the array members are initialized correctly regardless of the way that I write the code?  I am porting this code from 
> windows and the same warning did not appear in the msvc compiler.  Is this a compiler dependent issue and am I just asking
> for trouble if the brackets are left out?
> 
> Thanks again!!
> 
> David Stroupe wrote:
> > 
> > When I compile this line of code
> > 
> > int JPEG_MRK_NTSC[4][4] =
> > {
> > 0x01, 0x02, 0x03, 0x04,
> > 0x05, 0x06, 0x07, 0x08,
> > 0x09, 0x0a, 0x0b, 0x0c,
> > 0x0d, 0x0e, 0x0f, 0x00
> > };
> > 
> >  with the -Wall option, I get the following warnings
> > 
> > vis.c:264: warning: missing braces around initializer
> > vis.c:264: warning: (near initialization for `JPEG_MRK_NTSC[0]')
> > 
> > If I look at the values of the array members during execution, they are
> > correct.
> > 
> > Is this array really being initialized correctly?
> > Are the warnings correct?
> > 
> > Is there a way to 'turn off' these particular warnings with a compiler
> > directive?
> > 
> >
> 
> -- 
> Best regards,
> David Stroupe
> Keyed-Up Software
> 5307 Faireast Court
> Arlington, Texas 76018-1683
> 817/557-4903 voice
> 817/472-0408 fax
> 
> 

Re: Array Initialization warnings

[David Stroupe]

>Hi David,
>
> The compiler is quite right, your initialiser is for
>an int JPEG_MRK_NTSC[16].
>
>Try something like;
>
>int JPEG_MRK_NTSC[4][4] =
> {
> {0x01, 0x02, 0x03, 0x04},
> {0x05, 0x06, 0x07, 0x08},
> {0x09, 0x0a, 0x0b, 0x0c},
> {0x0d, 0x0e, 0x0f, 0x00}
> };
>
>yours sincerely,
>
>bjorn

Thanks bjorn, indeed that eliminates the warnings and your explanation makes perfect sense.  Is it an accident...or just lucky,
that the array members are initialized correctly regardless of the way that I write the code?  I am porting this code from 
windows and the same warning did not appear in the msvc compiler.  Is this a compiler dependent issue and am I just asking
for trouble if the brackets are left out?

Thanks again!!

David Stroupe wrote:
> 
> When I compile this line of code
> 
> int JPEG_MRK_NTSC[4][4] =
> {
> 0x01, 0x02, 0x03, 0x04,
> 0x05, 0x06, 0x07, 0x08,
> 0x09, 0x0a, 0x0b, 0x0c,
> 0x0d, 0x0e, 0x0f, 0x00
> };
> 
>  with the -Wall option, I get the following warnings
> 
> vis.c:264: warning: missing braces around initializer
> vis.c:264: warning: (near initialization for `JPEG_MRK_NTSC[0]')
> 
> If I look at the values of the array members during execution, they are
> correct.
> 
> Is this array really being initialized correctly?
> Are the warnings correct?
> 
> Is there a way to 'turn off' these particular warnings with a compiler
> directive?
> 
>

-- 
Best regards,
David Stroupe
Keyed-Up Software
5307 Faireast Court
Arlington, Texas 76018-1683
817/557-4903 voice
817/472-0408 fax