Bug 325679

Description Kirk Beitz 2010-09-18 09:07:50 EDT

Created attachment 179174 [details]
addition of CodeBufferUnderflowException and use in recovering from underflow while parsing buffer of ARM code

at times, buffer underflow when parsing instructions on variable size ISAs can result in a lot of error messages populating the Disassembly view.

the attached patch was formerly part of a much larger patch in Bug 325284, but has been extracted due to that bug relying on Bug 325277.  it represents the simplest patch to HEAD as of 2010.09.17 w.r.t. performing this functionality.

currently, both of the 2 existing EDC disassembler instruction parsers (ARM & x86) translate a BufferUnderflowException into a CoreException, and this is handled in AbstractDisassembler#disassembleInstructions() by throwing a new CoreExcpetion() for callers to deal with.

this causes disassembleInstructions() to discard what may be a large buffer of properly parsed disassembly because the requester could not know a priori exactly how much to ask for.

the attached patch adds new CodeBufferUnderflowException extending CoreException, throws it from the ARM & x86 parsers, and catches/handles the new exception in disassembleInstructions() when not trying to disassemble the PC for stepping purposes and when at least one instruction was properly parsed.

by making CodeBufferUnderflowException an extension of CoreException:
a) any non-ARM & non-x86 @override extensions can still catch it and act the same
b) any non-ARM & non-x86 instruction parsers that still just throw CoreException and be caught in disassembleInstructions() as happens without this patch.

this patch applies cleanly to head as of 2010.09.18, and has been tested with the edc windows debugger; a modified version of the attached patch has been tested together with other disassembly changes, and is planned for later merge together at the same time.