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<p class="MsoNormal"><span style="font-size:11.0pt">GCC accepts the code below. Clang rejects it. Who is right?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">struct ovrMatrix4f {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">};<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">class Matrix4 {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">public:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> operator const ovrMatrix4f () const {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ovrMatrix4f result;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> return result;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">};<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">void ok() {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> Matrix4 from;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ovrMatrix4f to = from; // that one is fine<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">void bad() {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> Matrix4 from;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ovrMatrix4f to;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> to = from; // compilation fails here<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Clang says:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">test.cpp:20:8: error: no viable conversion from 'Matrix4' to 'ovrMatrix4f'<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> to = from; // compilation fails here<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ^~~~<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">test.cpp:1:8: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'Matrix4' to<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> 'const ovrMatrix4f &' for 1st argument<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">struct ovrMatrix4f {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ^<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">test.cpp:1:8: note: candidate constructor (the implicit move constructor) not viable: no known conversion from 'Matrix4' to<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> 'ovrMatrix4f &&' for 1st argument<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">struct ovrMatrix4f {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ^<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">test.cpp:6:3: note: candidate function<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> operator const ovrMatrix4f () const {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ^<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">test.cpp:1:8: note: passing argument to parameter here<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">struct ovrMatrix4f {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> ^<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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