c - Modification of const int through a non-const pointer -

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• can casting away constness lead undefined behavior? [duplicate] 5 answers

#include <stdio.h>  int main(){     const int = 10;     *(int*)(&a) = 9; // modify     printf("%d", a);     return 0; } 

• when run code on xcode, output 10 (not changed)
• when run code on visual studio community, output 9 (changed)

why?

q: why?

ans: undefined behaviour.

to explain, if try modify const variable value accessing through non-const pointer, invokes undefined behaviour.

as per c11 standard, chapter 6.7.3, paragraph 6.

if attempt made modify object defined const-qualified type through use of lvalue non-const-qualified type, behavior undefined.

note: recommended signature of main() int main(void).