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trifork / erjang

A JVM-based Erlang VM
http://www.erjang.org
Apache License 2.0
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Exception-related beam verification error #43

Closed eriksoe closed 14 years ago

eriksoe commented 14 years ago

The code: exn() -> try erlang:error(x) catch E -> {caught,E} after io:format("after\n") end.

results in this error: l(exntest). 13-11-2010 10:36:10 erjang.m.erlang.ErlBif load_module SEVERE: cannot load module exntest java.lang.RuntimeException: Verify error. Expected word in stack, but stack is empty at kilim.analysis.Frame.pop(Frame.java:231) at kilim.analysis.Frame.popWord(Frame.java:236) at kilim.analysis.BasicBlock.interpret(BasicBlock.java:613) at kilim.analysis.MethodFlow.dataFlow(MethodFlow.java:374) at kilim.analysis.MethodFlow.analyze(MethodFlow.java:126) at kilim.analysis.ClassFlow.analyze(ClassFlow.java:104) at kilim.analysis.ClassWeaver.weave(ClassWeaver.java:59) at kilim.analysis.ClassWeaver.(ClassWeaver.java:45) at erjang.beam.Compiler.compile(Compiler.java:104)

eriksoe commented 14 years ago

Appears to be related to beam-level knowledge that erlang:error() never returns. The compiler omits "try_end" in the beam code, for example; "try_end" is present if some other function is called instead: {'try',{y,1},{f,6}}. {'try',{y,0},{f,3}}. {move,{atom,x},{x,0}}.

eriksoe commented 14 years ago

Oops - wrong button. How to reopen?

krestenkrab commented 14 years ago

Yeo. There's some logic in the codegen for call_ext calling isTerminal or something and then injects a return insn in that case. Perhaps erlang:error/1 is missing there.

eriksoe commented 14 years ago

Yes - I remember introducing it, but failed to quickly locate it when searching for 'error' - no wonder then. I'll try to fix.

eriksoe commented 14 years ago

isTerminal is gone, apparently - I think the issue is that only tail calls has this special treatment at present.

eriksoe commented 14 years ago

This appears to be a kilim issue; the 'dup' in question is the first instruction in an exception handler block - where the stack isn't empty. FTR, the input to kilim passes jvmverifier.

eriksoe commented 14 years ago

Verified: It's not a beam verification issue at all; it is a kilim shortcoming. Kilim patch written, tested and sent to the maintainer.