[src/trunk]: src/tests/usr.bin/xlint/lint1 tests/lint: add more examples for ...

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/8e5bdec32401
branches:  trunk
changeset: 371894:8e5bdec32401
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sat Oct 15 21:19:15 2022 +0000

description:
tests/lint: add more examples for 'extra bits set to 0'

Seen in sys/external/bsd/compiler_rt/dist/lib/builtins/fp_lib.h:88.

diffstat:

 tests/usr.bin/xlint/lint1/msg_309.c |  29 ++++++++++++++++++++++++++++-
 1 files changed, 28 insertions(+), 1 deletions(-)

diffs (43 lines):

diff -r 8a44c7ad39dd -r 8e5bdec32401 tests/usr.bin/xlint/lint1/msg_309.c
--- a/tests/usr.bin/xlint/lint1/msg_309.c       Sat Oct 15 20:11:44 2022 +0000
+++ b/tests/usr.bin/xlint/lint1/msg_309.c       Sat Oct 15 21:19:15 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: msg_309.c,v 1.5 2022/06/17 06:59:16 rillig Exp $       */
+/*     $NetBSD: msg_309.c,v 1.6 2022/10/15 21:19:15 rillig Exp $       */
 # 3 "msg_309.c"
 
 // Test for message: extra bits set to 0 in conversion of '%s' to '%s', op '%s' [309]
@@ -25,6 +25,33 @@
                return 16;
 
        /*
+        * The integer constant is explicitly unsigned.  Even in this case,
+        * the code may have originated on a platform where 'x' had 32 bits
+        * originally, and the intention may have been to clear the lower 16
+        * bits.
+        */
+       /* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
+       if ((x & 0xffff0000U) != 0)
+               return 16;
+
+       /*
+        * Even if the expression is written as '& ~', which makes the
+        * intention of clearing the lower 16 bits clear, on a 32-bit
+        * platform the integer constant stays at 32 bits, and when porting
+        * the code to a 64-bit platform, the upper 32 bits are preserved.
+        */
+       /* expect+1: warning: extra bits set to 0 in conversion of 'unsigned int' to 'unsigned long long', op '&' [309] */
+       if ((x & ~0xffffU) != 0)
+               return 16;
+
+       /*
+        * Casting the integer constant to the proper type removes all
+        * ambiguities about the programmer's intention.
+        */
+       if ((x & (unsigned long long)~0xffffU) != 0)
+               return 16;
+
+       /*
         * In the remaining cases, the constant does not have its most
         * significant bit set, therefore there is no ambiguity.
         */