digitalmars.D.bugs - [Issue 5314] New: Wrong error message: struct within immutable member and postblit function
- d-bugmail puremagic.com (30/30) Dec 03 2010 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (15/15) Dec 03 2010 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (11/17) Dec 03 2010 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (12/12) Dec 03 2010 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (17/20) Dec 04 2010 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (7/7) Dec 04 2010 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (107/107) Dec 06 2010 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (11/11) May 01 2011 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (13/13) May 01 2011 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (11/11) May 04 2012 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (13/14) May 09 2012 http://d.puremagic.com/issues/show_bug.cgi?id=5314
- d-bugmail puremagic.com (26/26) Nov 03 2012 http://d.puremagic.com/issues/show_bug.cgi?id=5314
http://d.puremagic.com/issues/show_bug.cgi?id=5314
Summary: Wrong error message: struct within immutable member
and postblit function
Product: D
Version: D2
Platform: Other
OS/Version: Windows
Status: NEW
Severity: normal
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: rayerd.wiz gmail.com
PST ---
// a.d
struct ID
{
immutable int value;
this(this){}
}
void main() {}
$ dmd a.d
Error: this is not mutable
Error: this is not mutable
Error: this is not mutable
- No line number.
- Strange *three* error message.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Dec 03 2010
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=5314
Jonathan M Davis <jmdavisProg gmx.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jmdavisProg gmx.com
PST ---
I've noticed that a lot of errors get printed three times. I have no idea why.
Regardless, the error message is close to correct. The problem is, of course,
that value is immutable, not the this pointer, but the object as a whole is not
mutable, because value is immutable, so saying that this is not mutable is
essentially correct, if somewhat misleading. It needs a better error message,
but the one that's there isn't totally off.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Dec 03 2010
http://d.puremagic.com/issues/show_bug.cgi?id=5314 PST ---I've noticed that a lot of errors get printed three times. I have no idea why. Regardless, the error message is close to correct. The problem is, of course, that value is immutable, not the this pointer, but the object as a whole is not mutable, because value is immutable, so saying that this is not mutable is essentially correct, if somewhat misleading. It needs a better error message, but the one that's there isn't totally off.Of course, I know that. I said that the error message has two problems. I didn't say that it is unkindness. However, it makes me happy if the message is more better, because the current message has not class and variable name. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 03 2010
http://d.puremagic.com/issues/show_bug.cgi?id=5314
nfxjfg gmail.com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |nfxjfg gmail.com
Are you saying this is not a rejects-valid?
I fail to see why structs with immutable members shouldn't be allowed to have a
postblit function.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Dec 03 2010
http://d.puremagic.com/issues/show_bug.cgi?id=5314 PST ---Are you saying this is not a rejects-valid?I think that this is maybe a rejects-invalid correctly. Error: this is not mutable Error: this is not mutable Error: this is not mutable However, this error message is bad clearly, because it hasn't line numbers and type/variable names. Of course, this message is strange that it is written by three times. For example, I think that a following sentence is more better. filename.d(4): struct ID has not both postblit and immutable member valueI fail to see why structs with immutable members shouldn't be allowed to have a postblit function.Uhmmm... I don't discuss the matter because it is other problem. But, we need probably discussion of the problem that you said. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 04 2010
http://d.puremagic.com/issues/show_bug.cgi?id=5314 PST --- - filename.d(4): struct ID has not both postblit and immutable member value + filename.d(4): struct ID cannot have both postblit and immutable member value -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 04 2010
http://d.puremagic.com/issues/show_bug.cgi?id=5314
PST ---
nfxjfg
This program shows when init, a constructor, the postblit constructor, and
opAssign are used:
import std.stdio;
struct Foo
{
int a = 7;
this(int a)
{
this.a = a;
writefln("constructor: %s", this.a);
}
this(this)
{
writefln("postblit: %s", this.a);
}
/+
Foo opAssign(const ref Foo other)
{
this.a = other.a;
writefln("opAssign: %s", this.a);
return this;
}
+/
}
void main()
{
writefln("%s(%s): -------", __FILE__, __LINE__);
Foo a;
writefln("%s(%s): -------", __FILE__, __LINE__);
auto b = Foo(6);
writefln("%s(%s): -------", __FILE__, __LINE__);
auto c = a;
writefln("%s(%s): -------", __FILE__, __LINE__);
b = c;
writefln("%s(%s): -------", __FILE__, __LINE__);
}
The output is:
test.d(29): -------
test.d(31): -------
constructor: 6
test.d(33): -------
postblit: 7
test.d(35): -------
postblit: 7
test.d(37): -------
Notice that assignment uses the postblit constructor. If you uncomment
opAssign(), then you get this instead:
test.d(29): -------
test.d(31): -------
constructor: 6
test.d(33): -------
postblit: 7
test.d(35): -------
opAssign: 7
test.d(37): -------
Now, assignment uses opAssign(). The problem with having an immutable member
variable and a postblit constructor is that you cannot reassign that member
variable. That portion of the struct cannot be altered.
If I changed the code to
import std.stdio;
struct Foo
{
immutable int a;
this(int a) immutable
{
this.a = a;
writefln("constructor: %s", this.a);
}
}
void main()
{
writefln("%s(%s): -------", __FILE__, __LINE__);
Foo a;
writefln("%s(%s): -------", __FILE__, __LINE__);
auto b = Foo(6);
writefln("%s(%s): -------", __FILE__, __LINE__);
auto c = a;
writefln("%s(%s): -------", __FILE__, __LINE__);
b = c;
writefln("%s(%s): -------", __FILE__, __LINE__);
}
then it fails to compile, giving the message
test.d(24): Error: variable test.main.b cannot modify immutable
The line b = c is illegal. Now, the line auto c = a is still legal, and you
could arguably allow a postblit constructor which didn't alter the immutable
member variables, but it does get a bit odd. You could arguably even allow for
assignment via opAssign() as long as the immutable member variable isn't
altered, but then it's probably not really copying, which would not be good.
So, I suppose that a postblit could be allowed in a struct with an immutable
member variable, but you couldn't assign to it or do a deep copy or do anything
with it that you'd normally do in a postblit constructor (though whether or not
that's a problem is debatable). But the compiler would have to be smart enough
to realize that having a postblit constructor didn't allow for assignment for
structs with immutable member variables, which may or may not be
straightforward, depending on how the compiler decides that it cannot do an
assignment to a struct with an immutable member variable.
All in all, copying structs with immutable member variables does tend to get a
bit funny. I suppose that a postblit constructor _could_ be allowed, but it is
a bit odd. Assignment certainly can't be allowed, and the postblit constructor
is assignment of a sort, but it could still work as long as it's only used when
constructing a variable. So, I don't know what the correct behavior is.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Dec 06 2010
http://d.puremagic.com/issues/show_bug.cgi?id=5314
kennytm gmail.com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ultimatemacfanatic gmail.co
| |m
*** Issue 5917 has been marked as a duplicate of this issue. ***
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 01 2011
http://d.puremagic.com/issues/show_bug.cgi?id=5314
kennytm gmail.com changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |diagnostic
CC| |kennytm gmail.com
OS/Version|Windows |All
Severity|normal |critical
Raising severity to "Critical" as per bug 5745.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 01 2011
http://d.puremagic.com/issues/show_bug.cgi?id=5314
SomeDude <lovelydear mailmetrash.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |lovelydear mailmetrash.com
Severity|critical |normal
PDT ---
Reducing criticity to normal, as diagnostic bugs are not critical.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 04 2012
http://d.puremagic.com/issues/show_bug.cgi?id=5314
Don <clugdbug yahoo.com.au> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |clugdbug yahoo.com.au
Severity|normal |critical
Reducing criticity to normal, as diagnostic bugs are not critical.
They're equivalent to compiler segfaults. Worse than any rejects-valid bug.
They're nearly always very easy to fix, too. There's no excuse for them.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 09 2012
http://d.puremagic.com/issues/show_bug.cgi?id=5314
Denis Shelomovskij <verylonglogin.reg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |verylonglogin.reg gmail.com
2012-11-03 15:16:46 MSK ---
Original example compiles fine now but is the issue fixed?
Can somebody familiar with dmd internals check if "%s is not mutable" error
message gives line now:
https://github.com/D-Programming-Language/dmd/blob/master/src/expression.c
main.d(29): -------
main.d(31): -------
constructor: 6
main.d(33): -------
postblit: 7
main.d(35): -------
opAssign: 7
postblit: 7 <- added line
main.d(37): -------
The line is added correctly and indicates a fixed compiler bug because
Foo opAssign(const ref Foo other)
returns by value so a temporary is created.
--
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Nov 03 2012