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diff --git a/Doc/Manual/CPlusPlus14.html b/Doc/Manual/CPlusPlus14.html index b162c7818..adca9b37d 100644 --- a/Doc/Manual/CPlusPlus14.html +++ b/Doc/Manual/CPlusPlus14.html @@ -15,6 +15,7 @@ <li><a href="#CPlusPlus14_core_language_changes">Core language changes</a> <ul> <li><a href="#CPlusPlus14_binary_literals">Binary integer literals</a> +<li><a href="#CPlusPlus14_return_type_deduction">Return type deduction</a> </ul> <li><a href="#CPlusPlus14_standard_library_changes">Standard library changes</a> </ul> @@ -53,6 +54,67 @@ int b = 0b101011; </pre> </div> +<H3><a name="CPlusPlus14_return_type_deduction">8.2.2 Return type deduction</a></H3> + + +<p> +C++14 added the ability to specify <tt>auto</tt> for the return type of a function +and have the compiler deduce it from the body of the function (in C++11 you had +to explicitly specify a trailing return type if you used <tt>auto</tt> for the +return type). +</p> + +<p> +SWIG parses these types of functions, but with one significant limitation: SWIG +can't actually deduce the return type! If you want to wrap such a function +you will need to tell SWIG the return type explicitly. +</p> + +<p> +The trick for specifying the return type is to use <tt>%ignore</tt> to tell +SWIG to ignore the function with the deduced return type, but first provide +SWIG with an alternative declaration of the function with an explicit return +type. The generated wrapper will wrap this alternative declaration, and the +call in the wrapper to the function will call the actual declaration. Here is +an actual example: +</p> + +<div class="code"><pre> +std::tuple<int, int> va_static_cast(); +%ignore va_static_cast(); +#pragma SWIG nowarn=SWIGWARN_CPP14_AUTO + +%inline %{ +#include <tuple> + +auto va_static_cast() { + return std::make_tuple(0, 0); +} +%} +</pre></div> + +<p> +For member methods the trick is to use <tt>%extend</tt> to redeclare the method and call it as follows: +</p> + +<div class="code"><pre> +%extend X { + const char * a() const { return $self->a(); } +} +%inline %{ +struct X { + auto a() const { + return "a string"; + } +}; +%} +</pre></div> + +<p> +<b>Compatibility note:</b> SWIG-4.2.0 first introduced support for functions declared with an auto return without a trailing return type. +</p> + + <H2><a name="CPlusPlus14_standard_library_changes">8.3 Standard library changes</a></H2> |