commit 34167aa6b0d7d53016b8574b4fe1fac764ddf615
from: Russ Cox <rsc@swtch.com>
date: Tue Mar 04 04:37:12 2008 UTC

lib9: gcc-4.2 bug in sprint

commit - b32d9d9c2e07681450a7ea1801b07e5727fa39e2
commit + 34167aa6b0d7d53016b8574b4fe1fac764ddf615
blob - 9e3cb63ec060f5859dedb96bf4d89a5626e8e7fd
blob + 4155d88597e543f89a4371f78688a5f79771694d
--- src/lib9/fmt/sprint.c
+++ src/lib9/fmt/sprint.c
@@ -16,8 +16,11 @@ sprint(char *buf, char *fmt, ...)
 	/*
 	 * on PowerPC, the stack is near the top of memory, so
 	 * we must be sure not to overflow a 32-bit pointer.
+	 *
+	 * careful!  gcc-4.2 assumes buf+len < buf can never be true and
+	 * optimizes the test away.  casting to uintptr works around this bug.
 	 */
-	if(buf+len < buf)
+	if((uintptr)buf+len < (uintptr)buf)
 		len = -(uintptr)buf-1;
 
 	va_start(args, fmt);