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digitalmars.D.learn - Why it doesn't compile in D 2.0?
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
}
void main(char[][] args) {
}
Error:
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
Is there workaround?
BR
Marcin Kuszczak
(aarti_pl)
aarti_pl <aarti interia.pl> wrote:
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
}
void main(char[][] args) {
}
Error:
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
Is there workaround?
Constant strings are saved in the static data segment of the executable, so
the .dup call would need to be executed at runtime. In other words, what
this would do is cast const to mutable.
If this did compile, changing the contents of t2 would change those
contents
for all instances of Test, which I assume is not your intention.
As for the workaround, write a constructor:
class Test {
string t1 = "test";
string t2;
this( ) {
t2 = "test".dup;
}
}
--
Simen
W dniu 2010-01-16 13:26, Simen kjaeraas pisze:
aarti_pl <aarti interia.pl> wrote:
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
}
void main(char[][] args) {
}
Error:
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
Is there workaround?
Constant strings are saved in the static data segment of the executable, so
the .dup call would need to be executed at runtime. In other words, what
this would do is cast const to mutable.
If this did compile, changing the contents of t2 would change those
contents
for all instances of Test, which I assume is not your intention.
As for the workaround, write a constructor:
class Test {
string t1 = "test";
string t2;
this( ) {
t2 = "test".dup;
}
}
I want just simple initialization of variable. Casting of course is no
(sane) option.
Indeed, in case of classes your workaround will work.
But in case of struct? The same problem occurs for structs, but you can
not declare default constructor in structs...
IMHO .dup should work for initialization of classes/structs.
Any other ideas?
BR
Marcin Kuszczak
(aarti_pl)
On 01/16/2010 02:01 PM, aarti_pl wrote:
W dniu 2010-01-16 13:26, Simen kjaeraas pisze:
aarti_pl <aarti interia.pl> wrote:
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
}
void main(char[][] args) {
}
Error:
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
Is there workaround?
Constant strings are saved in the static data segment of the
executable, so
the .dup call would need to be executed at runtime. In other words, what
this would do is cast const to mutable.
If this did compile, changing the contents of t2 would change those
contents
for all instances of Test, which I assume is not your intention.
As for the workaround, write a constructor:
class Test {
string t1 = "test";
string t2;
this( ) {
t2 = "test".dup;
}
}
I want just simple initialization of variable. Casting of course is no
(sane) option.
Indeed, in case of classes your workaround will work.
But in case of struct? The same problem occurs for structs, but you can
not declare default constructor in structs...
IMHO .dup should work for initialization of classes/structs.
Any other ideas?
BR
Marcin Kuszczak
(aarti_pl)
Perhaps this is or should be a bug. You can override dup to work in ctfe:
char[] dup(string str)
{
return str.dup;
}
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
char[] t3 = "test".dup(); //Ok!
}
The spec even mentions it under ctfe:
6. as a special case, the following properties can be executed at
compile time:
.dup
.length
.keys
.values
http://www.digitalmars.com/d/2.0/function.html
W dniu 2010-01-16 15:30, Lutger pisze:
Perhaps this is or should be a bug. You can override dup to work in ctfe:
char[] dup(string str)
{
return str.dup;
}
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
char[] t3 = "test".dup(); //Ok!
}
The spec even mentions it under ctfe:
6. as a special case, the following properties can be executed at
compile time:
..dup
..length
..keys
..values
http://www.digitalmars.com/d/2.0/function.html
Thanks! I will use function dup() as a workaround for now, and will put
bug to bugzilla.
I still wonder what has CTFE to do with this case. Do you know?
I am asking because it's not possible in general case to initialize all
variables in classes/structs and in global namespace.
E.g. I had to use:
Serializer!(TextArchive) serializer;
static this() {
serializer = new typeof(serializer);
}
to initialize serializer. I am wondering if with better CTFE we could
get it working?
BR
Marcin Kuszczak
(aarti_pl)
On 01/16/2010 04:18 PM, aarti_pl wrote:
W dniu 2010-01-16 15:30, Lutger pisze:
Perhaps this is or should be a bug. You can override dup to work in ctfe:
char[] dup(string str)
{
return str.dup;
}
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
char[] t3 = "test".dup(); //Ok!
}
The spec even mentions it under ctfe:
6. as a special case, the following properties can be executed at
compile time:
..dup
..length
..keys
..values
http://www.digitalmars.com/d/2.0/function.html
Thanks! I will use function dup() as a workaround for now, and will put
bug to bugzilla.
I still wonder what has CTFE to do with this case. Do you know?
I am asking because it's not possible in general case to initialize all
variables in classes/structs and in global namespace.
E.g. I had to use:
Serializer!(TextArchive) serializer;
static this() {
serializer = new typeof(serializer);
}
to initialize serializer. I am wondering if with better CTFE we could
get it working?
BR
Marcin Kuszczak
(aarti_pl)
ctfe is basically a user defined extension of constant folding, which is
also mentioned in the spec that way. So to use it for more complex
initialization makes sense, but this is constrained to compile time.
From the example of the serializer, all we know is that it allocates
memory. Array dup-ing also allocates memory however, so theoretically I
see no immediate reason why it would not (eventually) be possible to use
ctfe in that case. But it may be difficult to prove statically by the
compiler that it is indeed safe to do so.
aarti_pl wrote:
W dniu 2010-01-16 15:30, Lutger pisze:
Perhaps this is or should be a bug. You can override dup to work in ctfe:
char[] dup(string str)
{
return str.dup;
}
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
char[] t3 = "test".dup(); //Ok!
}
The spec even mentions it under ctfe:
6. as a special case, the following properties can be executed at
compile time:
..dup
..length
..keys
..values
http://www.digitalmars.com/d/2.0/function.html
Thanks! I will use function dup() as a workaround for now, and will put
bug to bugzilla.
I still wonder what has CTFE to do with this case. Do you know?
I am asking because it's not possible in general case to initialize all
variables in classes/structs and in global namespace.
E.g. I had to use:
Serializer!(TextArchive) serializer;
static this() {
serializer = new typeof(serializer);
}
to initialize serializer. I am wondering if with better CTFE we could
get it working?
BR
Marcin Kuszczak
(aarti_pl)
The next DMD release will have *major* CTFE improvements. I believe this
will work in the next release. (D1 couldn't compile it before, it can
now; I think D2 will be the same).
On 01/17/2010 01:38 AM, Simen kjaeraas wrote:
Lutger <lutger.blijdestijn gmail.com> wrote:
Perhaps this is or should be a bug. You can override dup to work in ctfe:
char[] dup(string str)
{
return str.dup;
}
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
char[] t3 = "test".dup(); //Ok!
}
The problem with this approach is that you now have a pointer to mutable
data, the contents of which are stored in the static data segment, and thus
actually immutable.
Second (and this is related to the first), the pointer will be the same for
all instances, and thus changing the contents of one will change the
contents of all.
IOW, what one (probably) wants in this situation, is a constructor.
Thanks man, this is a big error of mine. Trying to manipulate the char[]
does indeed do a segfault! I can't seem to find an explanation in the
spec of how initializers are supposed to work, so I assumed incorrectly
it would be ok.
I find it a bit disturbing that you can end up with a mutable reference
to immutable data so easily, without casting or anything.
W dniu 2010-01-17 12:54, Lutger pisze:
On 01/17/2010 01:38 AM, Simen kjaeraas wrote:
Lutger <lutger.blijdestijn gmail.com> wrote:
Perhaps this is or should be a bug. You can override dup to work in
ctfe:
char[] dup(string str)
{
return str.dup;
}
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
char[] t3 = "test".dup(); //Ok!
}
The problem with this approach is that you now have a pointer to mutable
data, the contents of which are stored in the static data segment, and
thus
actually immutable.
Second (and this is related to the first), the pointer will be the
same for
all instances, and thus changing the contents of one will change the
contents of all.
IOW, what one (probably) wants in this situation, is a constructor.
Thanks man, this is a big error of mine. Trying to manipulate the char[]
does indeed do a segfault! I can't seem to find an explanation in the
spec of how initializers are supposed to work, so I assumed incorrectly
it would be ok.
I find it a bit disturbing that you can end up with a mutable reference
to immutable data so easily, without casting or anything.
Well, I don't get it...
IMHO .dup makes mutable copy of data (so copy of "test") in mutable area
of memory. And it should mean that every pointer points to different
area of memory...
Am I wrong?
BR
Marcin Kuszczak
(aarti_pl)
W dniu 2010-01-17 20:56, Simen kjaeraas pisze:
aarti_pl <aarti interia.pl> wrote:
Well, I don't get it...
IMHO .dup makes mutable copy of data (so copy of "test") in mutable
area of memory. And it should mean that every pointer points to
different area of memory...
Am I wrong?
You're mostly right. However, this happens at compile time, so the mutable
data is mutable no longer once its been stored in the executable. IOW,
"Test".dup is executed once at compile time, and the result stored in
Test.init. Then, at runtime, Test.init is copied onto each new instance of
the struct/class. "Test".dup is not executed at runtime.
As Lutger pointed out, this smells of a bug. Sadly, fixing that bug would
not overcome the problem of having no default constructors for structs.
--
Simen
Well, in such a case you are right. It's not what I would like to have...
It will be indeed source of bugs.
BR
Marcin Kuszczak
(aarti_pl)
Lutger <lutger.blijdestijn gmail.com> wrote:
Perhaps this is or should be a bug. You can override dup to work in ctfe:
char[] dup(string str)
{
return str.dup;
}
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
char[] t3 = "test".dup(); //Ok!
}
The problem with this approach is that you now have a pointer to mutable
data, the contents of which are stored in the static data segment, and thus
actually immutable.
Second (and this is related to the first), the pointer will be the same for
all instances, and thus changing the contents of one will change the
contents of all.
IOW, what one (probably) wants in this situation, is a constructor.
--
Simen
aarti_pl wrote:
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
}
void main(char[][] args) {
}
Error:
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
Is there workaround?
BR
Marcin Kuszczak
(aarti_pl)
Workaround: It works in dmd2, svn 337 and later <g>.
W dniu 2010-01-17 19:38, Don pisze:
aarti_pl wrote:
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
}
void main(char[][] args) {
}
Error:
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
Is there workaround?
BR
Marcin Kuszczak
(aarti_pl)
Workaround: It works in dmd2, svn 337 and later <g>.
Wow. I even could not report it as a bug. That is really fast bug fixing :-)
Could you please explain what has initialization of variables to do with
CTFE? As far as I understand it should be done on runtime... So why is
there compile time execution involved?
And other questions. Would it be possible to initialize more complex
types with better CTFE? I see it as quite major issue when I can not
write in class definition or in global scope:
auto serializer = new Serializer!(TextArchive)();
BR
Marcin Kuszczak
(aarti_pl)
aarti_pl wrote:
W dniu 2010-01-17 19:38, Don pisze:
aarti_pl wrote:
class Test {
string t1 = "test"; //Ok!
char[] t2 = "test".dup; //Compile error
}
void main(char[][] args) {
}
Error:
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
hello.d(3): Error: cannot evaluate _adDupT((&
D12TypeInfo_Aya6__initZ),"test") at compile time
Is there workaround?
BR
Marcin Kuszczak
(aarti_pl)
Workaround: It works in dmd2, svn 337 and later <g>.
Wow. I even could not report it as a bug. That is really fast bug fixing
:-)
It wasn't specifically a fix of this bug. Some long-standing CTFE
limitations were fixed, which make lots of things start working.
Could you please explain what has initialization of variables to do with
CTFE? As far as I understand it should be done on runtime... So why is
there compile time execution involved?
It shouldn't be happening. There's a bug somewhere.
And other questions. Would it be possible to initialize more complex
types with better CTFE? I see it as quite major issue when I can not
write in class definition or in global scope:
auto serializer = new Serializer!(TextArchive)();
If you can't do that now, that's a serious bug.
But classes will eventually work in CTFE.
aarti_pl <aarti interia.pl> wrote:
Well, I don't get it...
IMHO .dup makes mutable copy of data (so copy of "test") in mutable area
of memory. And it should mean that every pointer points to different
area of memory...
Am I wrong?
You're mostly right. However, this happens at compile time, so the mutable
data is mutable no longer once its been stored in the executable. IOW,
"Test".dup is executed once at compile time, and the result stored in
Test.init. Then, at runtime, Test.init is copied onto each new instance of
the struct/class. "Test".dup is not executed at runtime.
As Lutger pointed out, this smells of a bug. Sadly, fixing that bug would
not overcome the problem of having no default constructors for structs.
--
Simen
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DMDScript
Lutger <lutger.blijdestijn gmail.com> 