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digitalmars.D.bugs - [Issue 12959] New: nothrow should be required for extern(C) functions


          Issue ID: 12959
           Summary: nothrow should be required for extern(C) functions
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody puremagic.com
          Reporter: code dawg.eu

This issues pops up regularly and boils down to some simple insights.

D's exception handling mechanism can't unwind C function stacks because it
always requires a frame pointer. This means that in many cases throwing an
exception in a D function that was called from C will crash your program.
Therefor it is safer to require nothrow for D functions which are declared as

A C function cannot throw a D exception, so they should always be declared as

D callbacks passed to C functions have the same issues as D function called
directly from C, so any extern(C) callback should be declared as nothrow.

Sometimes extern(C) is used to bind two D functions without having to import
any modules. While this is a legitimate use-case and exception handling works
here, extern(D) bindings can be used instead (see [1]).

The conclusion of the above reasons is to always require nothrow when declaring
an extern(C) function.

The main reason why extern(C) is preferred over extern(D) is the more difficult
mangling. This could be simplified with the help of
http://dlang.org/phobos/core_demangle.html#.mangleFunc and a template to
declare extern(D) functions. This solution is also more type safe than
extern(C) bindings.

    alias _d_monitor_create = externDFunc!("rt.monitor._create", void

Jun 20 2014