Why can't I reference a character in a string that was previously cast to void?

To use pthreads, I us开发者_运维技巧ed as input a char* that was cast to void* as input. If it's later cast to (char*) it can be printed and used normally ( (char*)var ). However, if one does (char*)var[i], where 'i' will help us reference a character, it doesn't. Why?

e.g. MS says 'expression must be a pointer to a complete object type'.

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Because of operator precedence: the cast comes after the subscript operator.

You have to write ((char*)var)[i];.

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The cast, in this case, is lower precedence than the array indexing. Instead, you would have to do something like *((char *)var + i), but the clearest approach is probably to assign it to a temporary:

 char *str = var;
 printf("%c", str[i]);

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Try (char *) &var[i], but that simply gets reference from var[i]. You can't do (char *) var[i] as that actually tries to convert a char to (char *).