[D-runtime] Bug 3150: requires changes to rt/lifetime.d

[Don Clugston]

You can still make the change I suggested in the bug report, adding a
static assert to check that the sizes are the same, and doing a cast
to ulong via a cast(void *), instead of a direct cast.
BTW I can't see any reason for any of those functions to use C calling
conventions. I presume they only reason they use C is because they're
so ancient.


On 23 July 2010 18:47, Sean Kelly <sean at invisibleduck.org> wrote:
> That's why I never changed it myself :-)  The compiler needs to be changed to use the new functions.
>
> On Jul 23, 2010, at 8:54 AM, Steve Schveighoffer wrote:
>
>> I have a problem here.  If I change a function that returns a ulong to having it
>> return an Array struct, the compiler expects the caller to push a reference to
>> the return value on the stack, where it doesn't do that when returning a ulong.
>>
>> Easily demonstrated with this code:
>>
>> testlongtoarray2.d:
>> struct Array
>> {
>>    size_t length;
>>    ubyte* ptr;
>> }
>>
>> extern(C) Array callme()
>> {
>>    Array d;
>>    d.length = 5;
>>    d.ptr = null;
>>    return d;
>> }
>>
>> testlongtoarray.d:
>> extern(C) ulong callme();
>>
>> void main()
>> {
>>    ulong x = callme();
>> }
>> [steves at steveslaptop testd]$ dmd -gc testlongtoarray*.d[steves at steveslaptop
>> testd]$ gdb testlongtoarray2
>> GNU gdb (GDB) Fedora (6.8.50.20090302-40.fc11)
>> Copyright (C) 2009 Free Software Foundation, Inc.
>> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
>> This is free software: you are free to change and redistribute it.
>> There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
>> and "show warranty" for details.
>> This GDB was configured as "i586-redhat-linux-gnu".
>> For bug reporting instructions, please see:
>> <http://www.gnu.org/software/gdb/bugs/>...
>> (gdb) run
>> Starting program: /home/steves/testd/testlongtoarray2
>> [Thread debugging using libthread_db enabled]
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x08049073 in callme (__HID1=0x180fc4) at testlongtoarray2.d:9  <------ note the
>> hidden argument which is garbage!
>> 9        Array d;
>> Missing separate debuginfos, use: debuginfo-install glibc-2.10.2-1.i686
>> (gdb)
>>
>> What's happening is that main is simply calling the function without pushing
>> anything on the stack, but the implementation expects that the reference to the
>> return value is on the stack.
>>
>> Does this make any sense to anyone?  What should I do here?  I can't really
>> change what the compiler expects the return value to be.
>>
>> -Steve
>>
>>
>>
>> ----- Original Message ----
>>> From: Don Clugston <dclugston at googlemail.com>
>>> To: D-runtime at puremagic.com
>>> Sent: Fri, July 23, 2010 5:31:04 AM
>>> Subject: [D-runtime] Bug 3150: requires changes to rt/lifetime.d
>>>
>>> Fixing this bug will be important for 64 bits:
>>> 3150 cast from dynamic array  to ulong is allowed
>>>
>>> As discussed in the comments to that bug, a change is  required at two
>>> places in druntime, because druntime currently relies on the  compiler
>>> bug. I don't think it's particularly difficult, but I don't want to  do
>>> it myself. Can one of you guys take care of  it?
>>> _______________________________________________
>>> D-runtime mailing  list
>>> D-runtime at puremagic.com
>>> http://lists.puremagic.com/mailman/listinfo/d-runtime
>>>
>>
>>
>>
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