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Introduce a standard scheme for -Z flags based on existing -X and -Y flags #31
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PR #1 includes a way to list these options: |
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That was, like, three whole days ago... ;) |
puffnfresh
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to puffnfresh/scala
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this issue
Jul 30, 2015
In Scala 2.8.2, an optimization was added to create a static
cache for Symbol literals (ie, the results of `Symbol.apply("foo"))`.
This saves the map lookup on the second pass through code.
This actually was broken somewhere during the Scala 2.10 series,
after the addition of an overloaded `apply` method to `Symbol`.
The cache synthesis code was made aware of the overload and brought
back to working condition recently, in scala#3149.
However, this has uncovered a latent bug when the Symbol literals are
defined with traits.
One of the enclosed tests failed with:
jvm > t8933b-run.log
java.lang.IllegalAccessError: tried to access field MotherClass.symbol$1 from class MixinWithSymbol$class
at MixinWithSymbol$class.symbolFromTrait(A.scala:3)
at MotherClass.symbolFromTrait(Test.scala:1)
This commit simply disables the optimization if we are in a trait.
Alternative fixes might be: a) make the static Symbol cache field
public / b) "mixin" the static symbol cache. Neither of these
seem worth the effort and risk for an already fairly situational
optimization.
Here's how the optimization looks in a class:
% cat sandbox/test.scala; qscalac sandbox/test.scala && echo ":javap C" | qscala;
class C {
'a; 'b
}
Welcome to Scala version 2.11.5-20141106-145558-aa558dce6d (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_20).
Type in expressions to have them evaluated.
Type :help for more information.
scala> :javap C
Size 722 bytes
MD5 checksum 6bb00189166917254e8d40499ee7c887
Compiled from "test.scala"
public class C
{
public static {};
descriptor: ()V
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=0, args_size=0
0: getstatic typelevel#16 // Field scala/Symbol$.MODULE$:Lscala/Symbol$;
3: ldc typelevel#18 // String a
5: invokevirtual typelevel#22 // Method scala/Symbol$.apply:(Ljava/lang/String;)Lscala/Symbol;
8: putstatic typelevel#26 // Field symbol$1:Lscala/Symbol;
11: getstatic typelevel#16 // Field scala/Symbol$.MODULE$:Lscala/Symbol$;
14: ldc typelevel#28 // String b
16: invokevirtual typelevel#22 // Method scala/Symbol$.apply:(Ljava/lang/String;)Lscala/Symbol;
19: putstatic typelevel#31 // Field symbol$2:Lscala/Symbol;
22: return
public C();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial typelevel#34 // Method java/lang/Object."<init>":()V
4: getstatic typelevel#26 // Field symbol$1:Lscala/Symbol;
7: pop
8: getstatic typelevel#31 // Field symbol$2:Lscala/Symbol;
11: pop
12: return
}
fixup
milessabin
pushed a commit
that referenced
this issue
Jul 31, 2017
Non local returns aren't eliminated after inlined in 2.11 or 2.12
```
⚡ scala
Welcome to Scala 2.12.1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.
scala> @inlune def foo(a: => Any) = if ("".isEmpty) a else ""
<console>:11: error: not found: type inlune
@inlune def foo(a: => Any) = if ("".isEmpty) a else ""
^
scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any
scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn
scala> :javap -c InlineReturn#test
public java.lang.Object test();
Code:
0: new #4 // class java/lang/Object
3: dup
4: invokespecial #32 // Method java/lang/Object."<init>":()V
7: astore_1
8: getstatic #36 // Field $line4/$read$$iw$$iw$.MODULE$:L$line4/$read$$iw$$iw$;
11: aload_1
12: invokedynamic #59, 0 // InvokeDynamic #0:apply:(Ljava/lang/Object;)Lscala/Function0;
17: invokevirtual #63 // Method $line4/$read$$iw$$iw$.foo:(Lscala/Function0;)Ljava/lang/Object;
20: goto 44
23: astore_2
24: aload_2
25: invokevirtual #66 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
28: aload_1
29: if_acmpne 39
32: aload_2
33: invokevirtual #69 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
36: goto 41
39: aload_2
40: athrow
41: goto 44
44: areturn
Exception table:
from to target type
8 20 23 Class scala/runtime/NonLocalReturnControl
```
```
⚡ ~/scala/2.11.8/bin/scala
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.
scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any
scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn
scala> :javap -c InlineReturn#test
public java.lang.Object test();
Code:
0: new #4 // class java/lang/Object
3: dup
4: invokespecial #13 // Method java/lang/Object."<init>":()V
7: astore_1
8: getstatic #19 // Field .MODULE$:L;
11: new #21 // class InlineReturn$$anonfun$test$1
14: dup
15: aload_0
16: aload_1
17: invokespecial #24 // Method InlineReturn$$anonfun$test$1."<init>":(LInlineReturn;Ljava/lang/Object;)V
20: invokevirtual #28 // Method .foo:(Lscala/Function0;)Ljava/lang/Object;
23: goto 39
26: astore_2
27: aload_2
28: invokevirtual #31 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
31: aload_1
32: if_acmpne 40
35: aload_2
36: invokevirtual #34 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
39: areturn
40: aload_2
41: athrow
Exception table:
from to target type
8 26 26 Class scala/runtime/NonLocalReturnControl
scala> :quit
```
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Many new features of Typelevel Scala will be "hidden" behind compiler flags, which will behave like the existing -X and -Y flags of mainline Scalac. We need a standard way of defining and implementing these.
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