Re: SysTime bug or feature?
On Tuesday, 6 October 2015 at 05:54:44 UTC, Jonathan M Davis wrote: It is by design, albeit undesirable. When SysTime was originally written, it was impossible to have a default value for a class reference other than null. So, unless SysTime was going to take the performance hit of constantly checking whether its TimeZone was null, SysTime.init was going to segfault if you did anything with it that required its TimeZone. And I wasn't about to have it constantly checking for null. In the vast majority of cases, the value of a SysTime comes from Clock.currTime() or from parsing a string, and if code is trying to do anything but assign to a SysTime which is SysTime.init, then that means that it failed to initialize it like it should have. Thanks for thorough explanation. I found the problem using vibe and REST API with SysTime argument with default value (which didn't work due to the bug there) when I tried to print out the passed value and ended up with the segfault. So I guess it doesn't bite devs often as it is mostly used as you wrote.
SysTime bug or feature?
This code:
import std.stdio;
import std.datetime;
void main()
{
SysTime t = SysTime.init;
writeln(t);
}
results in segfault with dmd-2.068.2
Is it ok?
Backtrace:
#0 0x004733f3 in std.datetime.SysTime.adjTime() const ()
#1 0x004730b9 in std.datetime.SysTime.toSimpleString()
const ()
#2 0x00473339 in std.datetime.SysTime.toString() const ()
#3 0x00463dc4 in
std.format.formatObject!(std.stdio.File.LockingTextWriter,
std.datetime.SysTime, char).formatObject(ref
std.stdio.File.LockingTextWriter, ref std.datetime.SysTime, ref
std.format.FormatSpec!(char).FormatSpec) ()
#4 0x00463cb7 in
std.format.formatValue!(std.stdio.File.LockingTextWriter,
std.datetime.SysTime,
char).formatValue(std.stdio.File.LockingTextWriter, ref
std.datetime.SysTime, ref
std.format.FormatSpec!(char).FormatSpec) ()
#5 0x00463c5a in
std.format.formatGeneric!(std.stdio.File.LockingTextWriter,
std.datetime.SysTime,
char).formatGeneric(std.stdio.File.LockingTextWriter,
const(void)*, ref std.format.FormatSpec!(char).FormatSpec)---Type
to continue, or q to quit---
()
#6 0x00463b63 in
std.format.formattedWrite!(std.stdio.File.LockingTextWriter,
char,
std.datetime.SysTime).formattedWrite(std.stdio.File.LockingTextWriter, const(char[]), std.datetime.SysTime) ()
#7 0x00463675 in
std.stdio.File.write!(std.datetime.SysTime,
char).write(std.datetime.SysTime, char)
()
#8 0x00463591 in
std.stdio.writeln!(std.datetime.SysTime).writeln(std.datetime.SysTime) ()
#9 0x00461b38 in D main ()
Re: SysTime bug or feature?
On Monday, October 05, 2015 18:12:06 tchaloupka via Digitalmars-d-learn wrote:
> This code:
>
> import std.stdio;
> import std.datetime;
>
> void main()
> {
> SysTime t = SysTime.init;
> writeln(t);
> }
>
> results in segfault with dmd-2.068.2
>
> Is it ok?
It is by design, albeit undesirable. When SysTime was originally written, it
was impossible to have a default value for a class reference other than
null. So, unless SysTime was going to take the performance hit of constantly
checking whether its TimeZone was null, SysTime.init was going to segfault
if you did anything with it that required its TimeZone. And I wasn't about
to have it constantly checking for null. In the vast majority of cases, the
value of a SysTime comes from Clock.currTime() or from parsing a string, and
if code is trying to do anything but assign to a SysTime which is
SysTime.init, then that means that it failed to initialize it like it should
have.
At some point in the last couple of years, it became possible to directly
initialize a class reference that was a member variable (or static, or at
module level, etc.) with an immutable class object. So, when the issue that
you're bringing up was brought up last year, I tried to create a new
TimeZone class that would specifically be for SysTime.init so that
SysTime.init would still be unique (so that st is SysTime.init would still
work properly), and it would print out "SysTime.init" for toString and be
treated as 1-01-01T00:00:00+00:00 for most everything else, but a
compiler bugs with regards to Rebindable made it so that it didn't work.
I need to take another stab at it and see if it works now, but until the
compiler issue is resolved, SysTime.init will continue to segfault if you do
anything with it which requires its TimeZone to be used (which includes
toString).
- Jonathan M Davis
