C++0x: Mangling of decltype

[Doug Gregor]

Continuing the string of manglings for C++0x, I propose the following
mangling schemes for decltype. decltype is like "typeof", and is
described here:

  http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2115.pdf

There are two mangling rules:

  <type> ::= Dt <expression> E  # decltype of an id-expression or
class member access (C++0x)
             ::= DT <expression> E  # decltype of an expression (C++0x)

We need two rules because decltype behaves differently for
id-expressions and class member accesses vs. full expressions. For
example:

  int x;
  decltype(x) y1; // y1 has type "int"
  decltype((x)) y2; // y2 has type "int &"

A patch to the ABI document is below.

  - Doug

diff -u orig/abi-mangling.html ./abi-mangling.html
--- orig/abi-mangling.html	2007-07-11 09:21:46.000000000 -0400
+++ ./abi-mangling.html	2007-07-11 09:28:02.000000000 -0400
@@ -50,6 +50,8 @@
 <tr><td>oper</td> <td>d</td> <td> v </td> <td> Operator / </td> </tr>
 <tr><td>oper</td> <td>d</td> <td> V </td> <td> Operator /= </td> </tr>
 <tr><td>type</td> <td>D</td> <td> p </td> <td> pack expansion of
(C++0x) </td> </tr>
+<tr><td>type</td> <td>D</td> <td> t </td> <td> decltype of an
id-expression or class member access (C++0x) </td> </tr>
+<tr><td>type</td> <td>D</td> <td> T </td> <td> decltype of an
expression (C++0x) </td> </tr>
 <tr><td>obj </td> <td>D</td> <td> 0 </td> <td> Deleting destructor</td> </tr>
 <tr><td>obj </td> <td>D</td> <td> 1 </td> <td> Complete object
(in-charge) destructor</td> </tr>
 <tr><td>obj </td> <td>D</td> <td> 2 </td> <td> Base object
(not-in-charge) destructor</td> </tr>
diff -u orig/abi.html ./abi.html
--- orig/abi.html	2007-07-11 09:21:41.000000000 -0400
+++ ./abi.html	2007-07-11 09:27:23.000000000 -0400
@@ -4156,6 +4156,8 @@
 	 ::= G <type>	# imaginary (C 2000)
 	 ::= U <source-name> <type>	# vendor extended type qualifier
          ::= Dp <type>  # pack expansion of (C++0x)
+         ::= Dt <expression> E  # decltype of an id-expression
or class member access (C++0x)
+         ::= DT <expression> E  # decltype of an expression (C++0x)
   <CV-qualifiers> ::= [r] [V] [K] 	# restrict (C99), volatile, const

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