C / C++ / MFC

Assigning the max Size for object arrays

23-Feb-06 6:03

See here.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

Spykraft23-Feb-06 3:33

Spykraft

23-Feb-06 3:33

Am working on VC 6.0, though have a small prob...
Suppose the declaration s like

classA[] obj = new classA[]{};

now when i try to access
int k = 0;
obj[k] = numeral;

it says array index out of bounds, tat means it needs a max size right?

so how do i define a max no of elements in the array size?

David Crow23-Feb-06 3:58

23-Feb-06 3:58

What about:

classA *obj = new ClassA[some_number];
obj[0] = numeral;
obj[1] = numeral;
...
obj[some_number-1] = numeral;

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

Spykraft23-Feb-06 4:13

Spykraft

23-Feb-06 4:13

Forgot to mention, have to dynamically increase/decrease the size of the array!

Cedric Moonen23-Feb-06 4:17

Cedric Moonen

23-Feb-06 4:17

Why don't you use a vector from the standard template library ? It offers all this flexibility and is much more secure.

Calling va_start Multiple Times...

toxcct23-Feb-06 4:18

toxcct

23-Feb-06 4:18

this is not VB, so no possible directly.
is you have to increase/decrease the size of your array you could either do it yourself :
- allocate a new array with the new size
- copy the elements to keep from the old array
- destroy the old array.

or use a library that already do that for you :
- std::vector<>
- std::list<>
- some other STL containers...

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.24][3.0 soon...]

James R. Twine23-Feb-06 3:12

James R. Twine

23-Feb-06 3:12

   For debugging purposes, I am going to be basically hijacking a function that handles a variable argument list. This function convers the Variable Argument List (VAL) into a va_list variable and passes it to another function to process the variable argument list (like how one would make a call to _vsntprintf).

   I can descern the number and types of arguments from other parameters passed to the function, so I want to be able to trace information on the parameters passed. My question is this - it is safe (not possible, but safe) to call va_start multiple times on the same va_list variable (in the same function) to reset the VAL?

   I cannot find code that does this, nor information that details the safety of doing so.

   Thoughts?

   Thanks!

   Peace!

-=- James

If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
DeleteFXPFiles & CheckFavorites (Please rate this post!)

peterchen23-Feb-06 5:06

peterchen

23-Feb-06 5:06

I've never encountered a mention of this scenario myself, but from the possibilities to implement this, it is OK. (the two implementation I've seen so far use a pointer to thestack, initialized by va_start, incremented by va_arg, and a do-nothing operation in va_end)

The question is: how portable do you need it?

Some of us walk the memory lane, others plummet into a rabbit hole

Tree<t> in C# || Fold With Us! || sighist

James R. Twine23-Feb-06 5:20

James R. Twine

23-Feb-06 5:20

   There are no portability concerns here - this is, and always will be, a Win32 implementation. Only concerns would be compiler differences if/when this implementation is built on a newer version of the compiler.

   My concern is one of works vs. correct. It might work, but is it correct to do so, so I will not expect any side-effects in the future.

   I do not expect it to be a problem, because va_start just resets the internal pointer to the beginning of the argument list, and there seems to be no other state stored outside of calls to va_arg, but it is always worth asking to make sure noone else has tried this and bombed! Smile | :)

Thanks!

Peace!

-=- James

peterchen23-Feb-06 6:24

peterchen

23-Feb-06 6:24

James R. Twine wrote:
but it is always worth asking to make sure noone else has tried this and bombed!

tell us if it does Wink | ;)

Some of us walk the memory lane, others plummet into a rabbit hole

Tree<t> in C# || Fold With Us! || sighist

Joe Woodbury23-Feb-06 9:08

Joe Woodbury

23-Feb-06 9:08

Not only safe, it's part of the design. To be technically correct, you should use va_end before using va_start the second time, though in VC++, it doesn't really matter (since it allocs no memory.)

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

Re: Writing a browser plugin

Ryan Binns23-Feb-06 14:58

Ryan Binns

23-Feb-06 14:58

James R. Twine wrote:
My question is this - it is safe (not possible, but safe) to call va_start multiple times on the same va_list variable (in the same function) to reset the VAL?

Yes. No problems at all. I've done it a few times. For safety, call va_end() in between, but in Win32, it's not required in any implementation I've seen. Other OSes might need it though.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

compiler setting

vaibhav shinde23-Feb-06 2:56

vaibhav shinde

23-Feb-06 2:56

I am geeting error
"cannot convert parameter 2 from 'char *' to 'LPCWSTR' Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast"

I think we need to change character set from UNICODE to MULTIBYTE( _MBCS instead of _UNICODE ) It gets compiled on VC6. The reason may be at that time the default character set wasn't Unicode.
I don't want to use _T() macro.

We can change character set through IDE this way-
Go to project properties, select ConfigurationProperties, General and you have an option called Character Set. The default is Use Unicode Character Set. Change it to Use Multi-Byte character set.

But how this can be done through command prompt. I need to use /d
to change option of cl.exe. But how exactly it is done?

Vaibhav

Re: compiler setting

vaibhav shinde23-Feb-06 2:58

vaibhav shinde

23-Feb-06 2:58

I am trying to build a project on VC2005. We work on command promt

Vaibhav

Writing a browser plugin

ice_and_fire23-Feb-06 2:55

ice_and_fire

23-Feb-06 2:55

Hello to all. I am searching for information about how I can create an additional plugin that can be installed on a browser. If anyone has an idea from where I might read something about how this is done I'll be very grateful for the help.
Regards, Tsvetelina Ivanova

David Crow23-Feb-06 2:56

23-Feb-06 2:56

Search for browser helper object (BHO).

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

Calling a function

srija23-Feb-06 2:22

srija

23-Feb-06 2:22

Am a novice in Vc++, actually, i wanted to call a function which outputs the data in Byte for repeted no of times to set the output data in an array(such a array of bytes), but am having compilation error? am using a "for loop" to call the function for no of times, until the output data is stored in an array. what am doing is right?is it possible to do so?

shrin

Re: Calling a function

toxcct23-Feb-06 2:27

toxcct

23-Feb-06 2:27

please show us your code to see what you're doing wrong, and tell exactly what the compiler returns you as an error !!

ps: put your code within <pre></pre> tags...

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.24][3.0 soon...]

Re: Calling a function

David Crow23-Feb-06 2:55