Félix, thanks for looking at this. I had a quick look through the IRInterpreter.
The implementation of Instruction::Load and Instruction::Store are probably okay, since they’re just moving data around. It also appears that when we read data into Scalars, we read it correctly, because we’re using EvaluateValue, which uses a properly-initialized DataExtractor. Writing data out of Scalars is also okay, because it uses GetAsMemoryData, which is parameterized with a byte order. As a result, I think the problem is localized to ResolveConstant. Your intuition was probably right: the data coming out of ResolveConstantValue needs to be byte-swapped before being written into memory. I’d do that right in ResolveConstant, by using a StreamString (initialized with flags = eBinary and addr_size and byte_order to match the target). If you can get me a patch I’ll be happy to review it. Sean On Sep 9, 2013, at 3:37 PM, Félix Cloutier <[email protected]> wrote: > Hello people again, > > Still working on that LLDB stub controlling a big-endian target. I'm working > on evaluating expressions. I just realized that lldb doesn't respect the > target byte order when it saves expression results. > > This expression: > > expr int $x = 4; > > causes lldb to allocate memory in the inferior process then write 04 00 00 00 > to it, which is little-endian for 4, even though my target is big endian. > > The ClangUserExpression was initialized with the correct byte order, but > things seem to go wrong with IRInterpreter::ResolveConstant, which calls > APInt::getRawData(), returning a pointer to an uint64_t in host byte order. > It then calls m_memory_map.WriteMemory, casting the uint64_t* into a > uint8_t*, and the rest is history. > > I guessed from the previous endianness bugs I reported that it could be fixed > with a SetByteOrder call, but turns out that there's no DataExtractor > involved. It could be swapped in IRMemoryMap::ResolveConstant, but I'm not > sure that's the correct thing to do. > > Félix > _______________________________________________ > lldb-dev mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev _______________________________________________ lldb-dev mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
