Sleigh NPE 'with blocks' with actions section

Describe the bug If an instruction inside a with block does not have an action section and the with block does, a NullPointerException occurs.

with : epsilon [ dummyContext=1; ] {
   :dummy is epsilon {}
}

Environment (please complete the following information):

• OS: Microsoft Windows [Version 10.0.18362.418]
• Java Version: 12.0.2
• Ghidra Version: 9.1

Additional context I traced it back to SleighCompiler.g line 601. b needs to be created if nil before the call to sc.pushWith but I’m not familiar with ANTLR so I’m unsure if it needs to happen before entering the withblock or just before calling pushWith.

[mumbel]

Unfortunate name collision looks like, they don’t have similar design/specs. There are also names that suggest it is example of sleigh/pcode (define pcodeop pcodeop_one;)

[SamuelWAnderson45]

Found a similar NPE related to operands.

with instruction : op0=1 & reg1 {
    :EXMPL reg1 is op1=0 {
    }
}

crashes with

ERROR Unrecoverable error(s), halting compilation (SleighCompile) java.lang.NullPointerException
	at ghidra.pcodeCPort.slgh_compile.SleighCompile.defineInvisibleOperand(SleighCompile.java:1159)
	at ghidra.sleigh.grammar.SleighCompiler.pequation_symbol(SleighCompiler.java:4458)
	at ghidra.sleigh.grammar.SleighCompiler.pequation(SleighCompiler.java:4293)
	at ghidra.sleigh.grammar.SleighCompiler.pequation(SleighCompiler.java:4137)
	at ghidra.sleigh.grammar.SleighCompiler.bitpattern(SleighCompiler.java:3562)
	at ghidra.sleigh.grammar.SleighCompiler.bitpat_or_nil(SleighCompiler.java:3301)
	at ghidra.sleigh.grammar.SleighCompiler.withblock(SleighCompiler.java:3168)
	at ghidra.sleigh.grammar.SleighCompiler.constructorlike(SleighCompiler.java:2963)
	at ghidra.sleigh.grammar.SleighCompiler.root(SleighCompiler.java:481)
	at ghidra.pcodeCPort.slgh_compile.SleighCompileLauncher.run_compilation(SleighCompileLauncher.java:373)
	at ghidra.pcodeCPort.slgh_compile.SleighCompileLauncher.runMain(SleighCompileLauncher.java:277)
	at ghidra.pcodeCPort.slgh_compile.SleighCompileLauncher.launch(SleighCompileLauncher.java:74)
	at ghidra.GhidraLauncher.main(GhidraLauncher.java:79)

Moving reg1 to the constructor like so

with instruction : op0=1 {
    :EXMPL reg1 is op1=0 & reg1 {
    }
}

allows the compilation to finish. After looking at the Sleigh spec, its unclear to me whether operands belong in the with block. Even in that case, the compilation should fail with a proper error, not an NPE.