On Sunday, 9 November 2014 at 15:09:10 UTC, H. S. Teoh via
Digitalmars-d wrote:
On Sun, Nov 09, 2014 at 08:29:58AM +0000, AlanThinker via
Digitalmars-d wrote:
It seems that, D's array is strange,
It can implicit convert static arrays to dynamic arrays no
error and
no warning.
But when I return the converted arrays out the function.
Outside function will get some wrong data.
It may very easily cause some bug because no error when
convert static
arrays to dynamic arrays.
[...]
Yes, this is a known problem. There may even be an issue filed
in
bugzilla about it (if not, please file one!). The problem is
that local
static arrays are allocated on the stack, and the implicit
conversion to
dynamic array is simply taking a slice of the stack-allocated
array. As
a result, after the function returns, the slice is now pointing
at stack
memory that has gone out of scope.
I'm not sure if the current compiler issues a warning / error
if you do
this in @safe code, but IMO it should do this even in @system
code since
the implicit conversion is almost never correct.
T
The problem is, that you need to be able to take a slice of a
stack-allocked array (otherwise stack allocated arrays are
useless). Eg you should be able to pass a slice of a stack array
to writefln().
Detecting if the slice is returned, requires flow analysis.
Currently the front-end doesn't do any flow analysis at all,
except for a couple of special cases like closures and super()
calls.
