In this review [1], Eli pointed out that we should be careful when
concatenating file names to avoid duplicated slashes. On Windows, a
double slash at the beginning of a file path has a special meaning. So
naively concatenating "/" and "foo/bar" would give "//foo/bar", which
would not give the desired results. We already have a few spots doing:
if (first_path ends with a slash)
path = first_path + second_path
else
path = first_path + slash + second_path
In general, I think it's nice to avoid superfluous slashes in file
paths, since they might end up visible to the user and look a bit
unprofessional.
Introduce the path_join function that can be used to join multiple path
components together (along with unit tests).
I initially wanted to make it possible to join two absolute paths, to
support the use case of prepending a sysroot path to a target file path,
or the prepending the debug-file-directory to a target file path. But
the code in solib_find_1 shows that it is more complex than this anyway
(for example, when the right hand side is a Windows path with a drive
letter). So I don't think we need to support that case in path_join.
That also keeps the implementation simpler.
Change a few spots to use path_join to show how it can be used. I
believe that all the spots I changed are guarded by some checks that
ensure the right hand side operand is not an absolute path.
Regression-tested on Ubuntu 18.04. Built-tested on Windows, and I also
ran the new unit-test there.
[1] https://sourceware.org/pipermail/gdb-patches/2022-April/187559.html
Change-Id: I0df889f7e3f644e045f42ff429277b732eb6c752
ffaebc199e