C programming doubt ?

@sachin-0wuUmc • Oct 25, 2024

Oct 25, 2024

1.5K

Hey guys,
If I execute the following code, what will happen ?
int *ptr;
ptr = malloc(100);
ptr++;
free(ptr);

Now ptr points to 2nd integer block.
Now if i use free ptr (as shown in code) what will it do ?
Will it free the whole 100 byte memory or something else ?

Please reply....😔

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gaurav.bhorkar

@gauravbhorkar-Pf9kZD • Jan 2, 2011

I think it will crash the program because you have created an invalid reference to the block of 100 bytes of allocated memory.

I'm not sure though. Did the program run?
0
csiscool

@csiscool-qA5mGA • Jan 2, 2011

Nice Question..

this code results in memory leak.
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Sachin Jain

@sachin-0wuUmc • Jan 2, 2011

@ csiscool
Can you please explain more ?
0
nansijs

@nansijs-Ulqfud • Apr 22, 2011

I think the program cause memory leak. That is the allocated memory cannot be used by another application.
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pradeep_agrawal

@pradeep-agrawal-rhdX5z • Apr 26, 2011

Based on ANSI C specification, if the argument passed to free does not matches with value returned by malloc/calloc/realloc, or if the space has already been freed by calling free or realloc then the behavior is undefined.

With this i feel the behavior can be different based on the compiler being used. If the code is compiled using gcc then the program will crash at free itself.

-Pradeep

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vik001ind

@vik001ind-rOaCSy • May 13, 2011

int *ptr; // this is a pointer of int type
ptr = malloc(100);
/* ERROR - malloc returns pointer of void type (void *), it is incompatible typecasting.
Correct statement - ptr = (int *)malloc(100); Here we are dynamically allocating an array of 50 integers (considering 16 bit compiler). */
ptr++; // PTR IS NOW POINTING TO NEXT INT
free(ptr); // ERROR - deallocating the pointer which contains the wrong address. Allocation of memory is done to different address.

Program may result in segmentation fault. Memory leak is a different concept altogether.
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PraveenKumar Purushothaman

@praveenkumar-66Ze92 • May 14, 2011

I got System Error and as said here, it caused a memory issue... Since I worked on a virtual machine, it crashed the system too. I used 64 MB of RAM and when I restarted it, it was fine. 😐 It causes a Segmentation Fault! 😀
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