[PATCH] Keep the symlink target alive while realpath_rec reads it
realpath_rec reads the names of a symlink target through a raw pointer
into the string returned by rb_readlink, while it calls itself to resolve
those names. RB_GC_GUARD(link_orig) keeps that string alive only for an
absolute target. For a relative target, link_orig is Qnil and nothing
uses `link` after the recursive call, so GC can free the string while the
later names are still being read.
File.realdirpath then returns a wrong path: the unresolved symlink path,
or a path with NUL bytes, which makes Pathname.new raise "pathname
contains null byte". CocoaPods calls Pathname#realdirpath for every
source file, and pnpm installs packages behind relative symlinks, so
`pod install` fails at random in such projects.
File.realpath is not affected on platforms with realpath(3), because only
RB_REALPATH_DIR uses realpath_rec there.
Fixes [Bug #22479]
nagachika
72d9d4b935