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Access Violation
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Join Date: Oct 2006
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Junior Poster in Training
Consider the following code:
When compiling with Borland C it worked fine. However when I tried cimpiling it with VS 2005 I got the following error:
"Unhandled exception at 0x00413529 in Learning C.exe: 0xC0000005: Access violation writing location 0x00415645."
When I changed the code to:
Instead of
It worked fine. I found this resolution in a forum.
But based on what I learnt in C I don't understand why it did not work in VS. And why by making it an array rather than a pointer it made a difference?
#include<stdio.h> #define SET_BIT(buf,n,val)buf[n]=val int main() { char ch='D'; char *name="Yankee Duddle"; int i=5; SET_BIT(name,i,ch); printf("%s",name); }
When compiling with Borland C it worked fine. However when I tried cimpiling it with VS 2005 I got the following error:
"Unhandled exception at 0x00413529 in Learning C.exe: 0xC0000005: Access violation writing location 0x00415645."
When I changed the code to:
char name[]="Yankee Duddle";
char *name="Yankee Duddle";
It worked fine. I found this resolution in a forum.
But based on what I learnt in C I don't understand why it did not work in VS. And why by making it an array rather than a pointer it made a difference?
In case
Whereas in case of
char *name="Yankee Duddle"; string literal turns into an unnamed, static array of characters, and this unnamed array may be stored in read-only memory, and which therefore cannot necessarily be modified. Trying to modify it is undefined behaviour. Whereas in case of
char name[]="Yankee Duddle"; you can modify the contents safely. 
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Originally Posted by amishosh 
When compiling with Borland C it worked fine. However when I tried cimpiling it with VS 2005 I got the following error:
"Unhandled exception at 0x00413529 in Learning C.exe: 0xC0000005: Access violation writing location 0x00415645."
But based on what I learnt in C I don't understand why it did not work in VS. And why by making it an array rather than a pointer it made a difference?
char name[]="Yankee Duddle"; the elements can be modified.
calling the SET_BIT in main you are trying to modify the value in char *name.
[EDIT]: Sorry, SPS your posted while I was writing this. Making this post a repetition.
Last edited by Aia; Aug 19th, 2007 at 1:35 pm.
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Junior Poster in Training
Why do the two compilers behave differently?
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Join Date: Oct 2006
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Junior Poster in Training
I think I found the answer (if anyone else has this problem):
http://msdn2.microsoft.com/en-us/lib...yy(vs.71).aspx
http://msdn2.microsoft.com/en-us/lib...yy(vs.71).aspx
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Join Date: Dec 2005
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> Why do the two compilers behave differently?
Because your code invokes undefined behaviour.
The assumption you made was that string constants can be modified, and they cannot.
If your code is correct, then you'll get the same answer with every compiler.
Because your code invokes undefined behaviour.
The assumption you made was that string constants can be modified, and they cannot.
If your code is correct, then you'll get the same answer with every compiler.
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