-@c Copyright (C) 1988,89,92,93,94,96 Free Software Foundation, Inc.
+@c Copyright (C) 1988,89,92,93,94,96,99 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
declarations and definitions.
* Template Instantiation:: Methods for ensuring that exactly one copy of
each needed template instantiation is emitted.
+* Bound member functions:: You can extract a function pointer to the
+ method denoted by a @samp{->*} or @samp{.*} expression.
* C++ Signatures:: You can specify abstract types to get subtype
polymorphism independent from inheritance.
+
@end menu
@node Naming Results
more discussion of these pragmas.
@end enumerate
+@node Bound member functions
+@section Extracting the function pointer from a bound pointer to member function
+
+@cindex pmf
+@cindex pointer to member function
+@cindex bound pointer to member function
+
+In C++, pointer to member functions (PMFs) are implemented using a wide
+pointer of sorts to handle all the possible call mechanisms; the PMF
+needs to store information about how to adjust the @samp{this} pointer,
+and if the function pointed to is virtual, where to find the vtable, and
+where in the vtable to look for the member function. If you are using
+PMFs in an inner loop, you should really reconsider that decision. If
+that is not an option, you can extract the pointer to the function that
+would be called for a given object/PMF pair and call it directly inside
+the inner loop, to save a bit of time.
+
+Note that you will still be paying the penalty for the call through a
+function pointer; on most modern architectures, such a call defeats the
+branch prediction features of the CPU. This is also true of normal
+virtual function calls.
+
+The syntax for this extension is
+
+@example
+extern A a;
+extern int (A::*fp)();
+typedef int (*fptr)(A *);
+
+fptr p = (fptr)(a.*fp);
+@end example
+
+You must specify @samp{-Wno-pmf-conversions} to use this extension.
+
@node C++ Signatures
@section Type Abstraction using Signatures