length of array

[prog00@googlemail.com]

Hi,
I write the following code:

void someproc() {
int controlids [] = {
IDC_BUTTON_RC_C ONNECT,
IDC_BUTTON_RC_C ONNECTPUBLIC,
IDC_BTN_SENDHEL LO };

someproc2(contr olids);
}

void someproc2(int * e)
{
int size = sizeof(e)/sizeof(int);
//.. do something with size.. like use in a for loop etc...

}

I expected to get the correct size, but it just gives me 1. What am I
doing wrong?

regards,

X.

[chenchen]

Re: length of array

because void someproc2(int * e) is wrong
in the scope e is changed to point type !
so int size = sizeof(e)/sizeof(int); size will == 1

[prog00@googlemail.com]

Re: length of array

So what should the signature of someproc2 be to make things right?

[Python.LeoJay@gmail.com]

Re: length of array

because array formal argument decays to a pointer to its first element
and the array bound is ignored.
so, IMHO, the only way to achieve your purpose is
void someproc() {
int controlids [] = {
IDC_BUTTON_RC_C ONNECT,
IDC_BUTTON_RC_C ONNECTPUBLIC,
IDC_BTN_SENDHEL LO };


someproc2(contr olids, sizeof(controli ds)/sizeof(controli ds[0]));



}


void someproc2(int * e, int size)
{
//.. do something with size.. like use in a for loop etc...


}

[prog00@googlemail.com]

Re: length of array

Alright, thanks.

X.

[Kai-Uwe Bux]

Re: length of array

prog00@googlema il.com wrote:
[color=blue]
> Hi,
> I write the following code:
>
> void someproc() {
> int controlids [] = {
> IDC_BUTTON_RC_C ONNECT,
> IDC_BUTTON_RC_C ONNECTPUBLIC,
> IDC_BTN_SENDHEL LO };
>
> someproc2(contr olids);
> }
>
> void someproc2(int * e)
> {
> int size = sizeof(e)/sizeof(int);
> //.. do something with size.. like use in a for loop etc...
>
> }
>
> I expected to get the correct size, but it just gives me 1. What am I
> doing wrong?[/color]

Your expectations were met: you got the correct size.

Note the signature: void someproc2(int * e ). You say that e is a variable
of type int*. Well, the size of a pointer to int on your machine just
happens to be the same as the size of an int. Note that the size of an int*
says nothing about the length of the array to whose first element that
pointer is pointing.


Best

Kai-Uwe Bux

ps.: If you want to keep track of the length of an array, consider using
std::vector.

[Tomás]

Re: length of array

[color=blue]
> void someproc() {
> int controlids [] = {
> IDC_BUTTON_RC_C ONNECT,
> IDC_BUTTON_RC_C ONNECTPUBLIC,
> IDC_BTN_SENDHEL LO };
>
> someproc2(contr olids);
> }
>
> void someproc2(int * e)
> {
> int size = sizeof(e)/sizeof(int);
> //.. do something with size.. like use in a for loop etc...
>
> }[/color]


Could use a template:


void someproc()
{
int controlids [] = {
IDC_BUTTON_RC_C ONNECT,
IDC_BUTTON_RC_C ONNECTPUBLIC,
IDC_BTN_SENDHEL LO };

someproc2(contr olids);
}

template<class T, unsigned i>
void someproc2(int (&array)[i])
{
int size = i;
}


-Tomás

[Default User]

Re: length of array

chenchen wrote:
[color=blue]
> because void someproc2(int * e) is wrong
> in the scope e is changed to point type !
> so int size = sizeof(e)/sizeof(int); size will == 1[/color]

Please read the information below.


Brian

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[Default User]

Re: length of array

prog00@googlema il.com wrote:
[color=blue]
> So what should the signature of someproc2 be to make things right?[/color]

Please read the information below.


Brian

--
Please quote enough of the previous message for context. To do so from
Google, click "show options" and use the Reply shown in the expanded
header.

[Default User]

Re: length of array

Python.LeoJay@g mail.com wrote:
[color=blue]
> because array formal argument decays to a pointer to its first element
> and the array bound is ignored.[/color]

Please read the information below.


Brian

--
Please quote enough of the previous message for context. To do so from
Google, click "show options" and use the Reply shown in the expanded
header.