If you are running against JDK 8 in a large scale Swing application you might eventually see the following exception, lots of lots of times. (Unless you forgot the lesson learned in my previous blog in your logging code, in which case you might see lots of ArrayOfOutBoundsException)
Caused by: java.lang.NullPointerException
at javax.swing.text.GlyphView.getBreakSpot(GlyphView.java:799)
at javax.swing.text.GlyphView.getBreakWeight(GlyphView.java:724)
at javax.swing.text.FlowView$LogicalView.getPreferredSpan(FlowView.java:733)
at javax.swing.text.FlowView.calculateMinorAxisRequirements(FlowView.java:233)
at javax.swing.text.ParagraphView.calculateMinorAxisRequirements(ParagraphView.java:717)
at javax.swing.text.BoxView.checkRequests(BoxView.java:935)
at javax.swing.text.BoxView.getMinimumSpan(BoxView.java:568)
at javax.swing.text.BoxView.calculateMinorAxisRequirements(BoxView.java:903)
at javax.swing.text.BoxView.checkRequests(BoxView.java:935)
at javax.swing.text.BoxView.setSpanOnAxis(BoxView.java:343)
at javax.swing.text.BoxView.layout(BoxView.java:708)
at javax.swing.text.BoxView.setSize(BoxView.java:397)
...
This error is particularly insidious because it takes around ten minutes to show itself and sometimes not at all. If you look at the code for this class the line in question, starts with "startsFrom = break", only accesses two local variables both of which have been previously referenced in the method.
Segment s = getText(pstart, pend);
s.first();
BreakIterator breaker = getBreaker();
breaker.setText(s);
// Backward search should start from end+1 unless there's NO end+1
int startFrom = end + (pend > end ? 1 : 0);
for (;;) {
startFrom = breaker.preceding(s.offset + (startFrom - pstart))
+ (pstart - s.offset);
if (startFrom > start) {
// The break spot is within the view
bs[ix++] = startFrom;
} else {
break;
}
}
The most direct way to rule out a JIT error is to disable compilation for just this single method, here is an example; but you can fine more in the documentation for the command line java tool.
javaThing -XX:CompileCommand=exclude,javax/swing/text/GlyphView,getBreakSpot
When this parameter is added, the problem goes away. - since we have ruled out enemy action by code or a concurrency issue we can be more sure this is a JIT issue. Now as part of the bug logging for this I output diagnostics for this single method, and found out that the problem, didn't occur until the method was JITted for a fifth time.
javaThing -XX:CompileCommand=print,javax/swing/text/GlyphView,getBreakSpot
Here is some diagnostic output seen with the above command:
Compiled method (c2) 914078 33142 4 javax.swing.text.GlyphView::getBreakSpot (247 bytes)
total in heap [0x00002aaab0749e10,0x00002aaab0750fe0] = 29136
relocation [0x00002aaab0749f38,0x00002aaab074a1e8] = 688
constants [0x00002aaab074a200,0x00002aaab074a2a0] = 160
main code [0x00002aaab074a2a0,0x00002aaab074cde0] = 11072
stub code [0x00002aaab074cde0,0x00002aaab074ce40] = 96
oops [0x00002aaab074ce40,0x00002aaab074ce58] = 24
metadata [0x00002aaab074ce58,0x00002aaab074d058] = 512
scopes data [0x00002aaab074d058,0x00002aaab074ea20] = 6600
scopes pcs [0x00002aaab074ea20,0x00002aaab0750c50] = 8752
dependencies [0x00002aaab0750c50,0x00002aaab0750c80] = 48
handler table [0x00002aaab0750c80,0x00002aaab0750e90] = 528
nul chk table [0x00002aaab0750e90,0x00002aaab0750fe0] = 336
OopMapSet contains 113 OopMaps
#0
OopMap{[8]=Oop [32]=Oop [40]=Oop off=892}
#1
OopMap{[32]=Oop [40]=Oop off=960}
#2
OopMap{[32]=Oop [40]=Oop off=980}
#3
OopMap{[32]=Oop [40]=Oop [48]=Oop off=1048}
#4
OopMap{[32]=Oop [40]=Oop [48]=Oop off=1084}
#5
OopMap{[0]=Oop [24]=Oop [48]=Oop [56]=Oop [80]=Oop off=2500}
#6
OopMap{rbx=Oop rdi=Oop [32]=Oop [40]=Oop [112]=Oop off=2533}
#7
OopMap{rbx=Oop rdi=Oop r14=Oop [32]=Oop [112]=Oop off=3081}
#8
OopMap{rbx=Oop rdi=Oop r14=Oop [32]=Oop [40]=Oop [112]=Oop off=3190}
#9
OopMap{[8]=Oop [32]=Oop [40]=Oop off=4408}
#10
OopMap{[32]=Oop [40]=Oop [48]=Oop off=4640}
#11
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop off=5232}
#12
OopMap{rbp=Oop [0]=NarrowOop [32]=Oop off=5364}
#13
OopMap{[32]=Oop [40]=Oop [48]=Oop off=5408}
#14
OopMap{rbp=Oop [32]=Oop [40]=Oop [48]=Oop off=5436}
#15
OopMap{rbp=Oop [32]=Oop [40]=Oop [48]=Oop off=5468}
#16
OopMap{rbp=Oop [32]=Oop [40]=Oop [48]=Oop off=5524}
#17
OopMap{rbp=Oop [32]=Oop [40]=Oop [48]=Oop [88]=Oop off=5552}
#18
OopMap{[32]=Oop [40]=Oop [48]=Oop [64]=Oop [72]=Derived_oop_[64] [112]=Oop off=5608}
#19
OopMap{[8]=Oop [32]=Oop off=5680}
#20
OopMap{rbp=Oop off=5720}
#21
OopMap{rbp=Oop off=5752}
#22
OopMap{rbp=Oop [24]=NarrowOop [28]=NarrowOop [32]=Oop [40]=Oop [48]=Oop [56]=Oop [64]=Oop [88]=Oop off=5812}
#23
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop [88]=Oop off=5960}
#24
OopMap{[0]=Oop [24]=Oop [48]=Oop [56]=Oop [72]=Oop [88]=NarrowOop off=6056}
#25
OopMap{[40]=Oop off=6088}
#26
OopMap{[0]=Oop off=6120}
#27
OopMap{[8]=Oop [24]=Oop [56]=Oop [72]=Oop [112]=Oop off=6216}
#28
OopMap{[0]=Oop [32]=NarrowOop [40]=Oop off=6284}
#29
OopMap{rbp=Oop [16]=Oop [40]=Oop [64]=Oop [112]=Oop off=6384}
#30
OopMap{[0]=Oop off=6412}
#31
OopMap{[0]=Oop [16]=Oop [32]=NarrowOop [40]=Oop [48]=Oop off=6488}
#32
OopMap{rbp=Oop [16]=Oop [40]=Oop [48]=Oop off=6560}
#33
OopMap{[32]=Oop [40]=Oop [48]=Oop [64]=Oop [112]=Oop off=6608}
#34
OopMap{[8]=Oop [28]=NarrowOop [32]=Oop [40]=Oop [48]=Oop off=6768}
#35
OopMap{rbp=NarrowOop [0]=Oop [16]=Oop [32]=Oop [40]=NarrowOop off=6860}
#36
OopMap{[0]=Oop [16]=Oop [32]=NarrowOop [40]=Oop [48]=Oop off=6988}
#37
OopMap{rbp=Oop [32]=Oop off=7024}
#38
OopMap{rbp=NarrowOop [0]=Oop [24]=Oop [32]=Oop off=7260}
#39
OopMap{rbp=NarrowOop [0]=Oop [24]=Oop [32]=Oop off=7344}
#40
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [60]=NarrowOop [64]=Oop off=7452}
#41
OopMap{rbp=NarrowOop [32]=Oop off=7476}
#42
OopMap{rbp=NarrowOop [0]=Oop off=7524}
#43
OopMap{[32]=Oop [40]=Oop [48]=Oop off=7588}
#44
OopMap{[32]=Oop [40]=Oop [48]=Oop off=7616}
#45
OopMap{[32]=Oop [40]=Oop [48]=Oop off=7632}
#46
OopMap{rbp=NarrowOop [32]=Oop off=7676}
#47
OopMap{rbp=NarrowOop [0]=Oop off=7724}
#48
OopMap{[0]=Oop [16]=Oop [28]=NarrowOop [40]=Oop [48]=Oop [56]=NarrowOop [64]=Oop off=7868}
#49
OopMap{[8]=Oop [28]=NarrowOop [32]=Oop [40]=Oop [48]=Oop [56]=Oop off=7916}
#50
OopMap{rbp=Oop [16]=Oop [24]=NarrowOop off=8016}
#51
OopMap{rbp=Oop [16]=Oop [28]=NarrowOop off=8080}
#52
OopMap{rbp=NarrowOop [0]=Oop [24]=Oop [32]=Oop off=8152}
#53
OopMap{rbp=Oop [8]=NarrowOop off=8212}
#54
OopMap{rbp=NarrowOop [32]=Oop off=8236}
#55
OopMap{rbp=Oop [16]=NarrowOop off=8272}
#56
OopMap{rbp=NarrowOop [0]=Oop off=8320}
#57
OopMap{rbp=Oop [12]=NarrowOop off=8360}
#58
OopMap{rbp=NarrowOop [32]=Oop off=8400}
#59
OopMap{rbp=Oop [12]=NarrowOop off=8460}
#60
OopMap{rbp=NarrowOop [0]=Oop off=8508}
#61
OopMap{rbp=Oop [24]=NarrowOop [40]=Oop off=8572}
#62
OopMap{rbp=Oop off=8600}
#63
OopMap{rbp=Oop [8]=Oop [28]=NarrowOop off=8640}
#64
OopMap{rbp=Oop [8]=Oop [20]=NarrowOop [112]=Oop off=8704}
#65
OopMap{rbp=Oop [16]=Oop [24]=Oop [48]=Oop off=8788}
#66
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop off=8912}
#67
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop off=9036}
#68
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop off=9160}
#69
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop off=9284}
#70
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop off=9408}
#71
OopMap{rbp=Oop [16]=Oop [24]=Oop [40]=Oop [64]=Oop off=9532}
#72
OopMap{off=9556}
#73
OopMap{off=9580}
#74
OopMap{off=9604}
#75
OopMap{[112]=Oop off=9628}
#76
OopMap{rbp=Oop [8]=Oop [24]=Oop [32]=NarrowOop off=9696}
#77
OopMap{rbp=Oop [8]=Oop [24]=NarrowOop off=9760}
#78
OopMap{off=9784}
#79
OopMap{off=9812}
#80
OopMap{off=9836}
#81
OopMap{off=9860}
#82
OopMap{off=9884}
#83
OopMap{off=9908}
#84
OopMap{off=9932}
#85
OopMap{off=9956}
#86
OopMap{off=9980}
#87
OopMap{off=10004}
#88
OopMap{off=10028}
#89
OopMap{rbp=Oop [16]=Oop [28]=NarrowOop off=10092}
#90
OopMap{rbp=Oop [16]=Oop [24]=Oop [48]=Oop off=10176}
#91
OopMap{off=10200}
#92
OopMap{off=10224}
#93
OopMap{off=10248}
#94
OopMap{off=10272}
#95
OopMap{off=10296}
#96
OopMap{off=10320}
#97
OopMap{off=10344}
#98
OopMap{off=10368}
#99
OopMap{off=10392}
#100
OopMap{off=10416}
#101
OopMap{off=10440}
#102
OopMap{off=10464}
#103
OopMap{off=10488}
#104
OopMap{off=10512}
#105
OopMap{off=10536}
#106
OopMap{off=10560}
#107
OopMap{off=10584}
#108
OopMap{off=10608}
#109
OopMap{off=10632}
#110
OopMap{off=10656}
#111
OopMap{off=10680}
#112
OopMap{off=11028}
java.lang.NullPointerException
at javax.swing.text.GlyphView.getBreakSpot(GlyphView.java:799)
at javax.swing.text.GlyphView.getBreakWeight(GlyphView.java:724)
at javax.swing.text.html.InlineView.getBreakWeight(InlineView.java:150)
at javax.swing.text.FlowView$LogicalView.getPreferredSpan(FlowView.java:733)
at javax.swing.text.FlowView.calculateMinorAxisRequirements(FlowView.java:233)
at javax.swing.text.ParagraphView.calculateMinorAxisRequirements(ParagraphView.java:717)
at javax.swing.text.html.ParagraphView.calculateMinorAxisRequirements(ParagraphView.java:157)
at javax.swing.text.BoxView.checkRequests(BoxView.java:935)
at javax.swing.text.BoxView.getMinimumSpan(BoxView.java:568)
at javax.swing.text.html.ParagraphView.getMinimumSpan(ParagraphView.java:270)
at javax.swing.text.BoxView.calculateMinorAxisRequirements(BoxView.java:903)
Now I am still working with the JDK team for a fix for this one; but I do feel I have discovered a useful set of tools for providing some evidence that the JIT compiler is causing my bad day. And more importantly I have a workaround so I can run my tests until this is resolved.
