What are void pointers in C?

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On paper, they seem like a weird concept... void pointer... as in... pointer to nothing? No, that's not it. In this video we'll explain what a void pointer actually is and how it can be used.

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7:15 It's important to notice that bytes are in reveresed order at each element. It's called small endian. For example if there wouldn't be small endian arrangement, the first element, 16, should be represented as { 00 00 00 00 00 00 00 10 }. Firstly it's not very noticeable in the case if you used 16, 31, 32, 65 or other numbers that can be represented as a byte but if you exceed that byte, the small endian arrangement will be noticable. Ex. (unsigned) 256 would be { 01 00 } but with small endian representation it's { 00 01 }. So this program is only good for these small numbers.

nandorboda

It's important to note that casting a pointer to a pointer of incompatible type is undefined behavior since it violates the C strict aliasing rule which is designed for code optimizations. You can however cast to and from void and char pointers and compatible pointer types. In particular 2:23 is erroneous (you can see that the compiler outputs a warning) but 8:04 technically isn't(the warning stays since the pointers are of different type but the code would always work fine and it isn't dangerous). GCC turns on this rule in -O2 and -O3 optimization levels with the -fstrict-aliasing flag.

martingeorgiev

Finally an accent which is understandable ^^' I really tried to follow all the indian dudes but sometimes I just wasn't sure I understand it correctly. They all made good videos (I think) but it was so hard to understand them, because they all try to beat eminem in saying the most english words in one minute xD

dracorep

honestly the way u explain pointers is very fascinating and easy to remember keep it up brother 😁

SafwanMashrafiSaraf-llwl

finally programming tutorials thtat can be watched on smartphone

gauravchaudhari

Thank you for this great video! Really enjoyed your presentation. As a novice C programmer, here's one (brute-force way) to specify to what type to cast the void pointer inside the function:

#include <stdio.h>

void printBytes(void*, int size);

int main(int argc, char *argv[])
{
int arr[] = { 16, 31, 32, 65 };
printBytes(arr, 4, sizeof(int));
}

void printBytes(void *arr, int size, int typeSize) {
for (int i = 0; i < size; i++) {
switch (typeSize) {
case 4:
// Cast the void pointer to appropriate type then dereference it to get it's value.
printf("%08x", ((int*)arr)[i]);
break;
default:
printf("????");
break;
}
printf("|");
}
}

Outputs:

shvideo