patch: add mangling for attribute enable_if

[Nick Lewycky]

On 03/09/2014 11:01 AM, David Majnemer wrote:
> Your std::remove_if would be more concise if it used a lambda instead
> of IsNotEnableIfAttr.

Done. Also added another test case to the mangling tests.

Nick

> On Sun Mar 09 2014 at 10:30:45 AM, Nick Lewycky <nicholas at mxc.ca
> <mailto:nicholas at mxc.ca>> wrote:
>
>     The attached mangle-enable_if-1.patch adds a mangling for
>     __attribute__((enable_if(expr, string-literal))) to clang.
>
>     demangle-enable_if-1.patch adds support to libcxxabi's demangler. This
>     patch I'm not very confident in. libcxxabi's cxa_demangle lacks comments
>     and assertions, leaving its design criteria a mystery. I think the
>     functions return 'first' in case of error. I added a vector<> inside the
>     demangler, I don't know whether that's OK because it means doing
>     allocation. I don't know what the two strings in the pair in db.names
>     are for, but the first one appears to be the demangling so I put it
>     there. I don't understand what the members in 'db' are for, since they
>     aren't commented (db.tag_templates?). The code is cargo culted from
>     parse_template_args and simplified down by making wild assumptions
>     (db.tag_templates is always false!) and constant folding.
>
>     Also the demangler seems pretty buggy. It wraps expressions in extra
>     parentheses which don't correspond to pi .. E expressions (if you were
>     to remangle it, you'd get the extra pi .. E). A mangling for "&function"
>     ends up demangling "&(function())" which has different semantic meaning.
>        I'm assuming these problems are pre-existing. While "_Z3foo"
>     demangles
>     to "foo" and "_Z3foov" demangles to "foo()", the same things with an
>     attribute demangle to include parens. For example, "_Z3fooUa3bar" and
>     "_Z3fooUa3barv" both demangle to "foo() __attribute__((bar))", never
>     "foo __attribute__((bar))".
>
>     Finally, I've never even compiled the change to the tests. I have tested
>     those exact manglings and seen what cxa_demangle does to them, but it
>     was easier to write a standalone tool than to deal with "testit".
>
>     Please review!
>
>     Nick
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