<div dir="ltr">On Wed, Oct 9, 2013 at 3:30 PM, Ted Kremenek <span dir="ltr"><<a href="mailto:kremenek@apple.com" target="_blank">kremenek@apple.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div class="im">On Oct 9, 2013, at 1:03 PM, Richard Trieu <<a href="mailto:rtrieu@google.com" target="_blank">rtrieu@google.com</a>> wrote:<br>
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Here is the code in question, template parameters fixed now:<br></div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
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template <int value></div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
int sum() {</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
  return value + sum<value/2>;</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
}</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
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template<></div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
int sum<1>() { return 1; }</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
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template<int x, int y></div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
int calculate_value() {</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
  if (x != y)</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
    return sum<x - y>();</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
  else</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
    return 0;</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
}</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
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int value = calculate_value<1,1>();</div><div style="font-family:HelveticaNeue;font-size:14px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
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calculate_value<1,1>() causes the instantiation of sum<0>(), even though it is protected from being called by the conditional "if (x != y)".  sum<0>() is the only self-recursive function here.  Are you saying we should warn on that even though the programmer added the proper check to prevent it from being called?</div>
</blockquote></div><br></div><div>Technically this should get folded out by the CFG builder.  It probably doesn’t handle it yet, but it could easily be taught to handle this specific case.  The CFG builder already prunes out some trivially unreachable paths.  This seems like one of those cases, since ‘x’ and ‘y’ are template parameters.</div>
</div></blockquote><div><br></div><div>I don't think that helps. sum<0> is still used, so we still instantiate it, and when we check its definition we would diagnose the infinite recursion.</div></div></div></div>