http://d.puremagic.com/issues/show_bug.cgi?id=4995

           Summary: invariant() can violate a function's nothrow
           Product: D
           Version: unspecified
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: jmdavisProg@gmx.com


--- Comment #0 from Jonathan M Davis <jmdavisProg@gmx.com> 2010-10-04 22:49:07 PDT ---
Take this program:

import std.stdio;

struct S
{
    int val() nothrow
    {
        return 7;
    }

    invariant()
    {
        throw new Exception("Hello from your friendly, neighborhood
invariant!");
    }
}

void main()
{
    auto s = S();
    writeln(s.val);
}


It results in this output:

object.Exception: Hello from invariant
----------------
./d(nothrow int d.S.val()) [0x807ece2]
./d(_Dmain+0x12) [0x807ed3a]
./d(extern (C) int rt.dmain2.main(int, char**)) [0x8084cd6]
./d(extern (C) int rt.dmain2.main(int, char**)) [0x8084c30]
./d(extern (C) int rt.dmain2.main(int, char**)) [0x8084d1a]
./d(extern (C) int rt.dmain2.main(int, char**)) [0x8084c30]
./d(main+0x96) [0x8084bd6]
/usr/lib32/libc.so.6(__libc_start_main+0xe6) [0xf7595c76]
./d() [0x807ec21]


This, in spite of the fact that val() is specifically marked as nothrow. This is particularly interesting since the compiler does complain about impure invariants (bug # 4974). Now, I hate to make invariants even pickier about whether they'll compile or let your struct/class compile, but this clearly violates the fact that val() is marked as nothrow. This program should not compile (or at least not with these semantics). I see two options:

1. The compiler should refuse to compile an invariant which throws if any function on the type is nothrow (very annoying, but possible necessary).

2. Merely change the generated code to consider any exception escaping the invariant to result in the invariant failing, as if you had

scope(FAILURE) assert(0, "Exception thrown in invariant.");

at the top of the invariant. This seems like a much nicer solution to me.


Regardless, the code which is currently generated is obviously wrong.

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http://d.puremagic.com/issues/show_bug.cgi?id=4995


Henning Pohl <henning@still-hidden.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull
                 CC|                            |henning@still-hidden.de


--- Comment #1 from Henning Pohl <henning@still-hidden.de> 2013-06-09 17:19:48 PDT ---
https://github.com/D-Programming-Language/dmd/pull/2155

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