<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><DIV><SPAN class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><BR class="Apple-interchange-newline"></SPAN> </DIV><BR><DIV><DIV>On Mar 26, 2007, at 5:53 PM, Neil Booth wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Christopher Lamb wrote:-</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV> <BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">It may even be incorrect for the compiler to enforce the semantics of <SPAN class="Apple-converted-space"> </SPAN></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">restrict pointers (with an error), even when the compilers alias <SPAN class="Apple-converted-space"> </SPAN></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">analysis determines that there is a may-alias relationship between to <SPAN class="Apple-converted-space"> </SPAN></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">pointers.<SPAN class="Apple-converted-space"> </SPAN></DIV> </BLOCKQUOTE><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">An error is an example of undefined behaviour.</DIV></BLOCKQUOTE></DIV><DIV><BR class="khtml-block-placeholder"></DIV>The point I was trying to make is that the 'restrict' qualifier stipulates the result of an alias query between to such qualified pointers. So even if the alias analysis returns that these two pointers may alias, it would not be correct to flag an error. This link has an example which may be useful <A href="http://www.lysator.liu.se/c/restrict.html#overlapping-objects">http://www.lysator.liu.se/c/restrict.html#overlapping-objects</A>.<BR><DIV><BR><DIV><DIV>--</DIV><DIV>Christopher Lamb</DIV><DIV><A href="mailto:christopher.lamb@gmail.com">christopher.lamb@gmail.com</A></DIV></DIV></DIV></BODY></HTML>