<div dir="rtl"><div dir="ltr">Compiling under Visual C++ 2012 with the default stack = 1MB, the stack overflows at depth of 216 instantiations, well before the 256 limit. Either the maximum depth needs to be lower or the Visual C++ stack needs to be larger using the /STACK:number_of_bytes linker parameter.</div>
<div dir="ltr"><br></div><div dir="ltr">In any case, the "recursive template instantiation exceeded maximum depth" error is followed by 256 notes where the instantiations happens...</div><div dir="ltr"><br></div>
<div dir="ltr">Yaron</div><div dir="ltr"><br></div></div><div class="gmail_extra"><div dir="ltr"><br><br><div class="gmail_quote">2013/9/20 Richard Smith <span dir="ltr"><<a href="mailto:richard@metafoo.co.uk" target="_blank">richard@metafoo.co.uk</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 .8ex;border-left:1px #ccc solid;border-right:1px #ccc solid;padding-left:1ex;padding-right:1ex">This is not endless recursion, just a stack overflow. I get:<div><br></div><div>
<div><stdin>:2:6: fatal error: recursive template instantiation exceeded maximum depth of 256</div><div>auto g(T x);</div>
<div> ^</div><div><stdin>:15:14: note: in instantiation of function template specialization 'f<double>' requested here</div><div> return x*f(x-1);</div><div> ^</div><div><stdin>:7:14: note: in instantiation of function template specialization 'g<double>' requested here</div>
<div> return x*g(x-1);</div><div> ^</div></div><div>[...]</div><div><br></div><div>This is not ideal, though. (There are a couple of other contexts where this kind of thing can happen, with constexpr and with decltype.) We should detect when we're recursively instantiating a function template specialization from within itself and bail out.</div>
</blockquote></div><div class="gmail_extra"><br><br><div class="gmail_quote"><div><div class="h5">On Thu, Sep 19, 2013 at 1:34 AM, Yaron Keren <span dir="ltr"><<a href="mailto:yaron.keren@gmail.com" target="_blank">yaron.keren@gmail.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="rtl"><div dir="ltr">Hello,</div><div dir="ltr"><br></div><div dir="ltr">The following code causes endless recursion leading to seg fault with the latest SVN. </div>
<div dir="ltr"><br></div><div dir="ltr">clang tries to deduce g return type, which requires f return type, which requires g return type, repeats endlessly.</div>
<div dir="ltr"><br></div><div dir="ltr">If the templates are modified to regular functions taking double, clang correctly errors upon parse:</div><div dir="ltr">error: function 'g' with deduced return type cannot be used before it is defined</div>
<div dir="ltr"><div dir="ltr"> return x*g(x-1);</div></div><div dir="ltr"><br></div><div dir="ltr">but with templates there is no error parsing, just seg fault running.</div><div dir="ltr"><br></div><div dir="ltr">Yaron</div>
<div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr"><div dir="ltr"><font face="courier new, monospace">// Endless recursion with revision 190992.</font></div><div dir="ltr"><font face="courier new, monospace"><br>
</font></div><div dir="ltr"><font face="courier new, monospace">template <class T></font></div><div dir="ltr"><font face="courier new, monospace">auto g(T x);</font></div><div dir="ltr"><font face="courier new, monospace"><br>
</font></div><div dir="ltr"><font face="courier new, monospace">template <class T></font></div><div dir="ltr"><font face="courier new, monospace">auto f(T x) {</font></div><div dir="ltr"><font face="courier new, monospace"> if (x>0)</font></div>
<div dir="ltr"><font face="courier new, monospace"> return x*g(x-1);</font></div><div dir="ltr"><font face="courier new, monospace"> else</font></div><div dir="ltr"><font face="courier new, monospace"> return 1.0;</font></div>
<div dir="ltr"><font face="courier new, monospace">}</font></div><div dir="ltr"><font face="courier new, monospace"><br></font></div><div dir="ltr"><font face="courier new, monospace">template <class T></font></div>
<div dir="ltr"><font face="courier new, monospace">auto g(T x) {</font></div><div dir="ltr"><font face="courier new, monospace"> if (x>0)</font></div><div dir="ltr"><font face="courier new, monospace"> return x*f(x-1);</font></div>
<div dir="ltr"><font face="courier new, monospace"> else</font></div><div dir="ltr"><font face="courier new, monospace"> return 1.0;</font></div><div dir="ltr"><font face="courier new, monospace">}</font></div><div><font face="courier new, monospace"><br>
</font></div><div><font face="courier new, monospace">int main() {</font></div><div><font face="courier new, monospace"> f(9.0);</font></div><div><font face="courier new, monospace">}</font></div><div><br></div></div></div>
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