From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bakul Shah <bakul@bitblocks.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Content-ID: <75565.1533108087.1@bitblocks.com>
Date: Wed,  1 Aug 2018 00:21:27 -0700
Message-Id: <20180801072134.DEB31156E400@mail.bitblocks.com>
Subject: [9fans] A compiler bug
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Consider:

% cat x.c
#include <u.h>
uintptr foo[3];
uintptr bar=&foo[2];

% 8c -c x.c	# this works.
% 5c -c x.c	# this fails
x.c:3 initializer is not a constant: bar

If I change the last line to

uintptr* bar=&foo[2];

Both compilers compile it fine. But if I change the last line
to

uintptr bar=(uintptr)&foo[2];

both compilers fail. Note that the last two examples are
type correct.

uintptr is the same size as int* so there should be no runtime
cost and we already know from the second example that &foo[2]
is a link time constant.

Similar code to the last two examples compiles on gcc/clang.

This seems like a compiler bug.