If we opened a file which was produced on system with different path
syntax, we would parse the paths from the debug info incorrectly.
The reason for that is that we would parse the paths as they were
native. For example this meant that on linux we would treat the entire
windows path as a single file name with no directory component, and then
we would concatenate that with the single directory component from the
DW_AT_comp_dir attribute. When parsing posix paths on windows, we would
at least get the directory separators right, but we still would treat
the posix paths as relative, and concatenate them where we shouldn't.
This patch attempts to remedy this by guessing the path syntax used in
each compile unit. (Unfortunately, there is no info in DWARF which would
give the definitive path style used by the produces, so guessing is all
we can do.) Currently, this guessing is based on the DW_AT_comp_dir
attribute of the compile unit, but this can be refined later if needed
(for example, the DW_AT_name of the compile unit may also contain some
useful info). This style is then used when parsing the line table of
that compile unit.
This patch is sufficient to make the line tables come out right, and
enable breakpoint setting by file name work correctly. Setting a
breakpoint by full path still has some kinks (specifically, using a
windows-style full path will not work on linux because the path will be
parsed as a linux path), but this will require larger changes in how
breakpoint setting works.