Q46947: Type of Expression "&arrayname" Changes under ANSI C

Article: Q46947
Product(s): See article
Version(s): 5.10   | 5.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | SR# G890706-22068 | mspl13_c
Last Modified: 26-JUL-1989

Question:

When I compile the following program

1:  void main(void)
2:      {
3:      char String[10];
4:      char *s;
5:
6:      s = &String;
7:      }

using Version 5.10 and the command line

   cl -W3 karma.c

the compiler generates the following message:

   karma.c(6) : warning C4046: '&' on function/array, ignored

This is consistent with historical C behavior. However, I understand
that ANSI C considers array names to be lvalues. The July 1989 MSJ
article "Pointers 101: Understanding and Using Pointers in the C
Language" validates this assumption. Does this mean that the "&" in
"&String" is no longer benign? Under ANSI C, does this give me (in
effect) a pointer to the address of "String"? What is the type and
value of the expression "&String"?

Response:

The 5.10 compiler ignores the "&", so the type of "&String" is the
same as "String", which is "pointer to char." This represents common
pre-ANSI behavior.

ANSI requires that the type of "&String" now be "pointer to array of
10 char." The next version of Microsoft C will conform to this
requirement.

However, aside from type warnings that may occur, this change IS
benign because the address generated is identical in either case --
the address of the zeroth element of the array. In other words, it
will not somehow generate the address of the address -- especially
since the address is a constant.

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