[Issue 3150] cast from dynamic array to ulong is allowed
https://issues.dlang.org/show_bug.cgi?id=3150 Andrei Alexandrescu and...@erdani.com changed: What|Removed |Added Version|D1 D2 |D2 --
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150 Walter Bright bugzi...@digitalmars.com changed: What|Removed |Added Status|NEW |RESOLVED CC||bugzi...@digitalmars.com Resolution||FIXED --- Comment #9 from Walter Bright bugzi...@digitalmars.com 2012-06-13 22:27:45 PDT --- Won't fix for D1, as that would change existing behavior. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150 --- Comment #8 from github-bugzi...@puremagic.com 2012-06-13 22:26:50 PDT --- Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/b0a0e35d23c996d6e068e2b859f2f51506f535f0 Issue 3150 - cast from dynamic array to ulong is allowed This patch makes this deprecated behavior. https://github.com/D-Programming-Language/dmd/commit/cc79fc96dc05742e07d03e4c575307f47f1d46dc Merge pull request #661 from yebblies/issue3150 Issue 3150 - cast from dynamic array to ulong is allowed -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150 yebblies yebbl...@gmail.com changed: What|Removed |Added CC||yebbl...@gmail.com Platform|Other |All Version|1.045 |D1 D2 AssignedTo|nob...@puremagic.com|yebbl...@gmail.com OS/Version|Linux |All --- Comment #7 from yebblies yebbl...@gmail.com 2012-01-30 18:21:30 EST --- druntime doesn't rely on this bug any more, and it isn't portable anyway. https://github.com/D-Programming-Language/dmd/pull/661 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150 --- Comment #2 from Don clugd...@yahoo.com.au 2010-05-10 02:00:27 PDT --- druntime currently relies on this behaviour in one place, and it's pretty nasty code. For example, it assumes pointers are 32 bits long. rt/lifetime.d _d_newarraymT() _d_newarraymiT() These both cast a void[] to a ulong. Instead of: result = cast(ulong)foo(ti, pdim, ndims); should be: static assert((void[]).sizeof == ulong.sizeof); void[] r = foo(ti, pdim, ndims); result = *cast(ulong *)r; In fact, this is a very ugly bit of code. It only seems to be used in e2ir.c, NewExp::toElem(), where there's another hack to get the .ptr out of the ulong. I don't see any reason why extern(D) couldn't be used instead, so that it could just return an array. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150 --- Comment #4 from Don clugd...@yahoo.com.au 2010-05-10 04:20:38 PDT --- (In reply to comment #3) Actually, you need a type besides a D array because you do not want to trigger runtime calls when setting the length. I don't understand this comment. A D array is used internally in the function. The function calculates a void[], and then casts this to ulong to return it. Then, in the compiler, it grabs the ulong back into a pointer. This all happens in the glue layer -- it's too late for any runtime calls to be added. Have I missed something? There might be opitmizations that the compiler makes when forming a ulong vs. some arbitrary type, I'll have to investigate that. Could be, but as far as I can tell, the dynamic array ABI is identical to ulong (result in EDX:EAX). So the compiler could probably cast it to ulong internally in e2ir.c, if there were any problems. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150 --- Comment #5 from Steven Schveighoffer schvei...@yahoo.com 2010-05-10 04:28:16 PDT --- Look at this part of the code, which actually writes the void[]: auto r = _d_newarrayT(ti, dim); // r is of type ulong p = *cast(void[]*)(r); This is inside the foo inner function (comment added by me). Care must be taken not to set the individual parts of the array because you can trigger runtime calls. I'm not saying that this means casting to/from ulong is the best solution, I'm just trying to explain why an actual D array may not be the most suitable type to use internally. I'm unsure why the foo function uses arrays internally, it clearly takes great pains not to trigger any runtime calls by using casting and the ptr member. I don't see why it can't do this with the Array struct type instead. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150 --- Comment #6 from Don clugd...@yahoo.com.au 2010-05-10 07:14:57 PDT --- (In reply to comment #5) Look at this part of the code, which actually writes the void[]: auto r = _d_newarrayT(ti, dim); // r is of type ulong p = *cast(void[]*)(r); This is inside the foo inner function (comment added by me). Care must be taken not to set the individual parts of the array because you can trigger runtime calls. I still don't see a problem. The only thing that code is doing, is casting from ulong back to void[]. That code should just be: p = _d_newarrayT(ti, dim); I'm not saying that this means casting to/from ulong is the best solution, I'm just trying to explain why an actual D array may not be the most suitable type to use internally. I'm unsure why the foo function uses arrays internally, it clearly takes great pains not to trigger any runtime calls by using casting and the ptr member. I don't see why it can't do this with the Array struct type instead. No, that's not the reason for the gymnastics in the code. The code is so old that when it was originally written, .ptr didn't exist for arrays (.ptr was added in DMD 0.107). The hack of casting to ulong is recent though (it doesn't exist in D1), and I think it's a bug. Although at first the code looks clever and magical, I think it's actually just an arcane legacy of a time when the language was very primitive and required lots of hacks. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3150] cast from dynamic array to ulong is allowed
http://d.puremagic.com/issues/show_bug.cgi?id=3150
Don clugd...@yahoo.com.au changed:
What|Removed |Added
Keywords|spec|accepts-invalid, patch
CC||clugd...@yahoo.com.au
--- Comment #1 from Don clugd...@yahoo.com.au 2010-05-07 22:57:16 PDT ---
Although types other than ulong currently generate error messages, they should
all be caught at the front end.
PATCH:
CastExp::semantic() in expression.c around line 7960 (DMD 2.045)
if (tobn-isTypeBasic() tobn-size() t1bn-size())
// Allow things like casting a long* to an int*
;
else if (tobn-ty != Tvoid)
// Cast to a pointer other than void*
goto Lunsafe;
}
// BUG: Check for casting array types, such as void[] to int*[]
}
+if (fromtype-ty == Tarray totype-ty != Tarray totype-ty !=Tvoid)
+{
+error(Cannot cast %s of type %s to %s, e1-toChars(),
e1-type-toChars(), to-toChars());
+return new ErrorExp();
+}
e = e1-castTo(sc, to);
return e;
}
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