DWARFDebugLoc: Make parsing and error reporting more robust
While examining this class for possible use in lldb, I noticed two
- it spits out parsing errors directly to stderr
- the loclists parser can incorrectly return valid location lists when parsing malformed (truncated) data
I improve the stderr situation by making the parseOneLocationList
functions return Expected<T>s. The errors are still dumped to stderr by
their callers, so this is only a partial fix, but it is enough for my
use case, as I intend to parse the locations lists one by one.
I fix the behavior in the truncated scenario by using the newly
introduced DataExtractor Cursor API.
I also add tests for handling the error cases, as they currently have no
Reviewers: dblaikie, JDevlieghere, probinson
Subscribers: lldb-commits, llvm-commits
Differential Revision: https://reviews.llvm.org/D63591