Does casting to char* and then casting back to original type break strict aliasing?

Question

For example, I cast a pointer to an int to a pointer to char:

int originalVar = 1;
char *arr = (char *)&originalVar;

Then I cast it back (maybe I pass arr to another function):

int *pOriginal = (int *)arr;

Does it break the rules? Or any undefined behaviors here?

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Actually my doubts are about understanding the "effective type" in C standard

Does the object pointed by arr always regard int as its effective type?

(Even if arr is passed to another function?)

Answer 1

That works and is well defined because the alignment of the original pointer will match the int.

Only issue casing a char* to an int* can be alignment requirements. Certain architectures require an int to be aligned on a 4-byte boundary (ie. the last two binary digits of the pointer are 0). A char* generally does not have that limitation.

However, since it started as an int*, and int* -> char* is never an issue, this will not cause any issue.