GCC 错误、错误代码或 gcc 是好的编译器

Question

I have this code:

int *b;
b = 50;
printf("Pointer point to address: %p and also point to this value: %d", b, *b);
return 0

I got this error: main.c:6:7: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
timeout: the monitored command dumped core
sh: line 1: 47524 Segmentation fault timeout 10s main

I wanna print value from fifty byte of memory.

Is my code right or will compiler do it work.

Answer 1

Assuming you are running the program on a recent OS like Linux, Mac or Windows, 50 will no be the bytes located at the address 50 in your physical memory ; that's an address in a virtual space.

Then your process (program) has only access to a very limited range in that virtual space, which 50 is unlikely to be from ; in that case the OS protects the illegal access and stops your process (segfault) ; anyway you could even get a result that may or may not be the correct one, this is called undefined behavior , and you better not rely in this case on a apparently working executable.

To access directly the physical memory, you either need to build a kernel module, or boot from a DOS-like OS, for instance.

main.c:6:7: warning: assignment makes pointer from integer without a cast [-Wint-conversion]

This being said, you need to cast 50 as a int * to clear the warning.

b = (int *)50;