Does it work with gdb?
It works with gdb. More info:
g++ & gdb – works, even without debuginfo for libstdc++
^ for std::string I’d expect this. For std::fstream, I expect you’d see the same problem/failure (gcc and clang both rely on fstream being homed in the standard library’s debug info (because of vtables/key functions), but clang takes it a step further and does this for std::string too (because of template explicit instantiation decl/def))
clang++ & gdb – works
g++ & lldb – works
^ again, I expect that would fail with std::fstream, demonstrating that the same problem exists for both clang and GCC, just clang takes it a bit further - but it’s not fundamentally different between the two.
clang++ & lldb – fails
I now notice these warnings in lldb after installing the debuginfo packages:
warning: (x86_64) /lib64/libstdc++.so.6 unsupported DW_FORM values:
warning: (x86_64) /lib64/libgcc_s.so.1 unsupported DW_FORM values: 0x1f20 0x1f21
I searched the web for details on that error, but came up empty.
Could it be that the debuginfo packages are just not compatible with
Ooh, yeah, that’s possible/likely. Unknown forms can’t be ignored because forms dictate the encoding, so without recognizing the form, the DWARF can’t be parsed (unknown /attributes/ using known forms are fine - because they can be parsed and the values ignored).
Yeah, looks like 1f20 (DW_FORM_GNU_ref_alt) and 1f21 (DW_FORM_GNU_strp_alt) are results of the ‘dwz’ tool that compacts DWARF debug info.
Not sure if it’d be enough to teach lldb how to parse but ignore any attribute using these forms - I would guess not, I suspect that would result in holes in the debug info where these forms are used. So you’d probably have to modify/fix/patch lldb to actually be able to understand these forms - which might not be too hard. Hmm, nope, probably fairly involved, since it means reading a new/different file (judging by this patch and the link to the DWARF standards proposal in it: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150518/277186.html ).
Yeah, short of making some relatively significant changes to lldb, I think you’ll probably just have to stick with larger debug info by using -fstandalone-debug, since the debug info provided by your distribution uses GNU extensions that lldb doesn’t currently support.