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Because the page in the process's virtual address space that str pointed to is not released right away. In fact it would probably get re-used if you immediately called new again.
In short: it's luck and it's a bug to access memory after using free/delete on it.
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The operator new allocates the space and assigns an address to the variable. The operator delete only marks that memory as re-usable, it does not change the assigned pointer. Your code will not throw any errors because all strcpy will do is check theat the address points to memory, it will not check if it is usable or not.
If in your test code you allocated and used more memory after deleteing str and before strcpy, you may find that the same memory is being used. The golden rule is, set the address to NULL directly after calling delete.
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thanks...
so better to follow the goldern rule.
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pyarigopal wrote: still its printing good_morning with out throwing any exception.
why this is happening ?
Perhaps delete is only marking the memory chunk as free and strcpy doesn't matter about, as stated by MSDN:
The strcpy function copies strSource, including the terminating null character, to the location specified by strDestination. No overflow checking is performed when strings are copied or appended
try this:
char *p = new char[100];
delete [] p;
char *q = new char[100];
strcpy(p,"Hello world\n");
strcpy(q,"Good news...\n");
printf("%s", p);
printf("%s", q);
if you're a lucky boy, like me, you will see the following output:
Good news...
Good news...
hence you're loosing the freed memory.
As already stated by other posters, NEVER DO SUCH NASTY THINGS.
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
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to add to all replies, use strcpy_s and take benefit of Security Enhancements in the CRT.
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Hi all,
I have creating dialog based window in vc++(MFC) and installed image magic(dynamic dll of binary version).
I need to know about InitializeMagic(char *) function. Is Magic must be initialize?... and when i read one image using read(std::string) function.....
#include Magick++.h<br />
#include iostream<br />
using namespace std;<br />
using namespace Magick; <br />
<br />
{<br />
Image img;<br />
img.read("c:\\logo.jpg");<br />
}
Error will be thrown like......
Unhandled exception at 0x000c256.. in sample.exe:0xC000075:
Access voilation writing location 0xcde....
Anybody know about this problem let me know...
Thankx in advance...
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I think you asked like this question you can also use of GDI+ or CImage class for read graphic files.(jpg,gif,png,..)
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Hi WhiteSky,
Just now i had read your previous reply, Sorry.......
I dont want that just read one image and save to another file. My target is convert multipage PDF file into image file with good resolution for OCR process. Can i use GDI+ or CImage for this conversion...
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I think no but see here[^] if its helpfuls
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But there is only Image to PDF converter
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Hi,
I need to write an injection module for my application.
Which one would be the best. Code Injection or DLL Injection. What are the advantages over the other...
Heard that, DLL injection can be used in all the windows OS. but code injection can be applied only on NT Operating sys.
Is there any other advantages or problems in using either of them..
Please advice me.
Thanks.
~ Selva
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To my mind "DLL injection" is a form of "Code Injection". If the code in question is complex DLL injection is the easiest way to get your code into another process. If you attempt to inject raw code you lose actions the loader performs which we all take for granted such as automatic code relocation; not to mention the fact that compilers build DLL's not "naked" code.
Steve
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Thanks Steve.
I will just go with DLL Injection in that case.
~ Selva
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Hello everyone,
I have designed a SDI application. I have assigned the title for the document using SetTitle() function in AbcDoc.cpp file.
I want to assign the title at runtime (i.e i have provided text box in a dialog). How should i do this?
Please help me.
Thanks in Advance.
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You can follow this root,
((CFrameWnd*)AfxGetMainWnd())->GetActiveDocument()->SetTitle("New");
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Thank You very much. It works..
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Assume I have a DLL with a function void BFunction(). I link this Dll to a program (test.exe) using its .lib and .h.
If, in the future, i add a new function to the Dll - void AFunction(), will i have to recompile test.exe even if test.exe does not (and will not) use the AFunction() ?
Since the Dll has changed, are the pointers to the functions in the dll are still the same? Or by adding a new function will cause existing programs to crash, and these existing programs must be recompiled as well?
Please help,
Thanks.
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You do not need to recompile test.exe until your new dll exports the function that is being called by test.exe
test.exe is only concerned about the function that it calls. No matter if you add or remove any other functions in the dll.
Nobody can give you wiser advice than yourself. - Cicero
ப்ரம்மா
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Does it mean, that i can keep on adding new functions to a dll (and export these functions) or modify the behavior of existing exported functions, and i do not have to recompile existing programs which are already linked to it?
Example
DLL ver1.0 - Functions : void BFunction(), void CFunction();
test.exe (calling BFunction()) is linked using .lib, .h during compile time to this DLL.
DLL ver 2.0 - Added function void AFunction(), and modified internal behavior of BFunction().
test.exe will still work fine? Since the function prototype of BFunction is still the same, test.exe should work fine right?
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1. You are free to add new functions always.
2. You are free to remove existing functions if those functions are not being used by the calling program.
3. You can modify the internal behavior of existing functions that are being used by the calling program, until you keep the return type and function parameters same.
uus831 wrote: Since the function prototype of BFunction is still the same, test.exe should work fine right?
Yes.
Nobody can give you wiser advice than yourself. - Cicero
ப்ரம்மா
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Thanks a lot. Now it's clear to me
Really appreciated it.
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If anyone else is using your DLL, it's not advisable to change the functionality of existing functions.
It might be a good idea to create/export classes for each interface version, and only add new functionality to new classes.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001
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Hello,
I using the Editbox as the Text editor and i assing the short cut keys in editbox for some operation like find text as Alt +H . How can i use it..
Manikandaprabu
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Have you tried using Keyboard Accelarators?
Nobody can give you wiser advice than yourself. - Cicero
ப்ரம்மா
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How to get the currrent view's bk color. I have used pDC->GetBkColor() in OnDraw() of the form view class but it gave white color.
How can this be done?
Thank you.
KIRAN PINJARLA
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