[Issue 13468] std.algorithm.canFind(null) fails with class
https://issues.dlang.org/show_bug.cgi?id=13468
--- Comment #3 from hst...@quickfur.ath.cx ---
Workaround:
Instead of using the default predicate a==b with null (i.e., effectively a
== null), use this instead:
if (canFind!a is null(b)) { ... }
--
[Issue 13468] std.algorithm.canFind(null) fails with class
https://issues.dlang.org/show_bug.cgi?id=13468
--- Comment #4 from hst...@quickfur.ath.cx ---
Alternate syntax:
if (canFind!((a) = a is null)(b)) { ... }
--
[Issue 13468] std.algorithm.canFind(null) fails with class
https://issues.dlang.org/show_bug.cgi?id=13468
hst...@quickfur.ath.cx changed:
What|Removed |Added
Keywords||wrong-code
Component|Phobos |DMD
--- Comment #5 from hst...@quickfur.ath.cx ---
Apparently I made a total fool of myself. The *real* reason for the bug is not
a.opEquals(b), but is caused by using == to compare a class reference to an
instance of typeof(null).
Specifically, this code works:
--
class C { }
bool fun(C e, C needle)
{
return (e == needle);
}
void main()
{
fun(null, null);
}
--
But this code segfaults:
--
class C { }
bool fun(C e, typeof(null) needle)
{
return (e == needle);
}
void main()
{
fun(null, null);
}
--
The only difference is that the segfaulting case takes `typeof(null)` as
parameter. Comparing class references with null is actually OK; what's *not* OK
is comparing them with an instance of typeof(null). I think this is a compiler
bug.
--
[Issue 13468] std.algorithm.canFind(null) fails with class
https://issues.dlang.org/show_bug.cgi?id=13468 hst...@quickfur.ath.cx changed: What|Removed |Added CC||hst...@quickfur.ath.cx --- Comment #1 from hst...@quickfur.ath.cx --- Found the cause of the bug. The problem is that when comparing two class references, the default predicate attempts to compare two class references with ==, which appears to dereference a NULL and cause a segfault. If a is b is used as predicate instead, there is no crash. Next is to find out why == doesn't handle null pointers correctly... --
[Issue 13468] std.algorithm.canFind(null) fails with class
https://issues.dlang.org/show_bug.cgi?id=13468 --- Comment #2 from hst...@quickfur.ath.cx --- Actually it's quite simple. The expression a == b, in the case of classes, is lowered into a.opEquals(b). Since a is null when find/canFind gets to a null element in the array, opEquals is invoked with a null this pointer, with disastrous consequences. --
[Issue 13468] std.algorithm.canFind(null) fails with class
https://issues.dlang.org/show_bug.cgi?id=13468 murphyslaw...@gmail.com changed: What|Removed |Added CC||murphyslaw...@gmail.com --
