Overhaul the mangling scheme to avoid ambiguities if the package path
contains a dot. Instead of using dot both to separate components and
to mangle characters, use dot only to separate components and use
underscore to mangle characters.
For golang/go#41862
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/271726
The current implementation of Gogo::pkgpath_for_symbol was written in
a way that allowed two distinct package paths to map to the same
symbol, which could cause collisions at link- time or compile-time.
Switch to a better mangling scheme to insure that we get a unique
packagepath symbol for each package. In the new scheme instead of having
separate mangling schemes for identifiers and package paths, the
main identifier mangler ("go_encode_id") now handles mangling of
both packagepath characters and identifier characters.
The new mangling scheme is more intrusive: "foo/bar.Baz" is mangled as
"foo..z2fbar.Baz" instead of "foo_bar.Baz". To mitigate this, this
patch also adds a demangling capability so that function names
returned from runtime.CallersFrames are converted back to their
original unmangled form.
Changing the pkgpath_for_symbol scheme requires updating a number of
//go:linkname directives and C "__asm__" directives to match the new
scheme, as well as updating the 'gotest' driver (which makes
assumptions about the correct mapping from pkgpath symbol to package
name).
Fixesgolang/go#27534.
Reviewed-on: https://go-review.googlesource.com/c/135455
From-SVN: r265510
