digitalmars.D.bugs - [Issue 6194] New: [GSoC] Destructor gets called on object before it is copied when calling writeln()
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http://d.puremagic.com/issues/show_bug.cgi?id=6194
Summary: [GSoC] Destructor gets called on object before it is
copied when calling writeln()
Product: D
Version: D2
Platform: All
OS/Version: Windows
Status: NEW
Severity: major
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: cristi.cobzarenco gmail.com
--- Comment #0 from Cristi Cobzarenco <cristi.cobzarenco gmail.com> 2011-06-22
08:46:01 PDT ---
import std.stdio;
import std.conv;
struct Test {
int x;
this( int m ) { x = m; }
this( this ) { writeln( "Postblit: ", x ); }
~this() { x = 42; }
string toString() { return to!string( x ); }
}
int main(string[] argv) {
auto a = Test(3);
writeln( a );
return 0;
}
When the running the code above, 42 gets printed instead of 3. Looking at the
"Postblit: " writes, one can see that the postblit ctor gets called 6 times and
only the last copy sets x to 42. It seems that at the last copy the destructor
gets called before the object gets blitted.
Using a debugger, I think I found the offending copy at line 1599 in file
format.d. Strangely, as much as I tried to reproduce the same kind of copying,
I could never get the bug to appear without using writeln.
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d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=6194
kennytm gmail.com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |kennytm gmail.com
--- Comment #1 from kennytm gmail.com 2011-06-22 09:51:21 PDT ---
Reduced:
---------------------------------------
struct Test {
int x;
~this() { x = 42; }
}
void formattedWrite(A...)(A args) {
Test* argsAddresses;
foreach (a; args) {
argsAddresses = &a;
assert(argsAddresses.x != 42, "line 9: unexpected: x == 42");
}
assert(argsAddresses.x != 42, "line 11: unexpected: x == 42");
}
int main(string[] argv) {
auto a = Test(3);
formattedWrite(a);
return 0;
}
---------------------------------------
core.exception.AssertError y.d(11): line 11: unexpected: x == 42
----------------
5 y 0x000087e9 onAssertErrorMsg + 73
6 y 0x00011be6 _d_assert_msg + 26
7 y 0x00001ab6 void
y.formattedWrite!(y.Test).formattedWrite(y.Test) + 138
8 y 0x00001944 _Dmain + 24
9 y 0x000122e3 extern (C) int
rt.dmain2.main(int, char**).void runMain() + 23
10 y 0x00011e8d extern (C) int
rt.dmain2.main(int, char**).void tryExec(scope void delegate()) + 29
11 y 0x0001232b extern (C) int
rt.dmain2.main(int, char**).void runAll() + 59
12 y 0x00011e8d extern (C) int
rt.dmain2.main(int, char**).void tryExec(scope void delegate()) + 29
13 y 0x00011e27 main + 179
14 y 0x00001921 start + 53
----------------
---------------------------------------
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--- Comment #2 from kennytm gmail.com 2011-06-22 10:33:34 PDT ---
I'm not sure if it's a bug in DMD or Phobos. I'm inclined to it's Phobos bug.
The loop variable 'a' in the reduced 'formattedWrite' is obviously escaping its
scope, so calling the destructor is reasonable. However, this is essentially
the implementation of std.format.formattedWrite:
1. the arguments are taken address
foreach (i, arg; args)
{
funs[i] = &formatGeneric!(Writer, typeof(arg), Char);
// We can safely cast away shared because all data is either
// immutable or completely owned by this function.
argsAddresses[i] = cast(const(void*)) &arg;
}
2. and then they are referred later for actual formatting.
{
funs[currentArg](w, argsAddresses[currentArg], spec);
++currentArg;
}
https://github.com/D-Programming-Language/phobos/blob/master/std/format.d#L302
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--- Comment #3 from Cristi Cobzarenco <cristi.cobzarenco gmail.com> 2011-06-24
04:23:28 PDT ---
(In reply to comment #2)
I'm not sure if it's a bug in DMD or Phobos. I'm inclined to it's Phobos bug.
The loop variable 'a' in the reduced 'formattedWrite' is obviously escaping its
scope, so calling the destructor is reasonable. However, this is essentially
the implementation of std.format.formattedWrite:
1. the arguments are taken address
foreach (i, arg; args)
{
funs[i] = &formatGeneric!(Writer, typeof(arg), Char);
// We can safely cast away shared because all data is either
// immutable or completely owned by this function.
argsAddresses[i] = cast(const(void*)) &arg;
}
2. and then they are referred later for actual formatting.
{
funs[currentArg](w, argsAddresses[currentArg], spec);
++currentArg;
}
https://github.com/D-Programming-Language/phobos/blob/master/std/format.d#L302
This works for me:
foreach (i, arg; args)
{
funs[i] = &formatGeneric!(Writer, typeof(arg), Char);
static if(hasAliasing!(typeof(arg)))
{
- argsAddresses[i] = &arg;
+ argsAddresses[i] = &args[i];
}
else
{
// We can safely cast away shared because all data is either
// immutable or completely owned by this function.
- argsAddresses[i] = cast(const(void*)) &arg;
+ argsAddresses[i] = cast(const(void*)) &args[i];
}
}
Unfortunately we can't replace the foreach with a for loop because we can't do
typeof( args[ i ] ). Does any one have any idea how we could avoid copying the
arguments needlessly?
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Jun 24 2011
http://d.puremagic.com/issues/show_bug.cgi?id=6194 --- Comment #4 from Cristi Cobzarenco <cristi.cobzarenco gmail.com> 2011-07-19 06:24:20 PDT --- Here's a pull request with my fix. https://github.com/D-Programming-Language/phobos/pull/151 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jul 19 2011
http://d.puremagic.com/issues/show_bug.cgi?id=6194
Kenji Hara <k.hara.pg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |k.hara.pg gmail.com
Resolution| |FIXED
--- Comment #5 from Kenji Hara <k.hara.pg gmail.com> 2011-07-31 13:44:37 PDT ---
https://github.com/D-Programming-Language/phobos/commit/d2541785e79fa67212cb8281122b14e38ea12ecf
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