Hi!

I thought at least in safe mode this code will not compile or I get warning:

byte[] func() @safe {
 byte[1024] buffer;
 return buffer[0..3];
}

void main() {
  auto b = func();
  b[0] = 1;
}

But no any error. Dlang do not catch this?

WBR,
    Fyodor.

On Tuesday, 27 January 2015 at 11:41:21 UTC, Fyodor Ustinov wrote:
> byte[] func() @safe {
>  byte[1024] buffer;
>  return buffer[0..3];
> }
>
> void main() {
>   auto b = func();
>   b[0] = 1;
> }

In 2.067, this is an error:

test.d(4,9): Error: escaping reference to local variable buffer

On Tuesday, 27 January 2015 at 11:51:43 UTC, Vladimir Panteleev wrote:
> In 2.067, this is an error:
>
> test.d(4,9): Error: escaping reference to local variable buffer

Always or only in safe mode?

On Tuesday, 27 January 2015 at 12:01:11 UTC, Fyodor Ustinov wrote:
> On Tuesday, 27 January 2015 at 11:51:43 UTC, Vladimir Panteleev wrote:
>> In 2.067, this is an error:
>>
>> test.d(4,9): Error: escaping reference to local variable buffer
>
> Always or only in safe mode?

Always. But the check seems very simple, and is easily circumvented. This compiles:

byte[] func() {
 byte[1024] buffer;
 auto p = buffer[0..3];
 return p;
}

Vladimir Panteleev:

> But the check seems very simple, and is easily circumvented. This compiles:
>
> byte[] func() {
>  byte[1024] buffer;
>  auto p = buffer[0..3];
>  return p;
> }

I guess such bugs will be detected (in safe code only!) after the implementation of: http://wiki.dlang.org/DIP69 Currently we are implementing a kind of pre-phase: http://wiki.dlang.org/DIP25

And here I have asked for @safe to become the default (Walter seems not against this idea):
https://d.puremagic.com/issues/show_bug.cgi?id=13838

Bye,
bearophile

On Tuesday, 27 January 2015 at 12:02:59 UTC, Vladimir Panteleev wrote:

> Always. But the check seems very simple, and is easily circumvented. This compiles:
>
> byte[] func() {
>  byte[1024] buffer;
>  auto p = buffer[0..3];
>  return p;
> }

I think this is the first step of a long and difficult way.

byte[] func(byte[] a) {
 return a[0..1];
}

byte[] func1() {
 byte[1024] buffer;
 return func(buffer[1...$]);
}

byte[] func2() {
 static byte[1024] buffer;
 return func(buffer[1..$]);
}