1 files changed, 83 insertions, 0 deletions
diff --git a/lib/portage/dep/libc.py b/lib/portage/dep/libc.py
new file mode 100644
index 000000000..db88432cb
--- /dev/null
+++ b/lib/portage/dep/libc.py
@@ -0,0 +1,83 @@
+# Copyright 2023 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+from portage.dep import Atom
+from portage.const import LIBC_PACKAGE_ATOM
+from portage.dbapi._expand_new_virt import expand_new_virt
+
+import portage.dbapi.porttree
+
+
+def find_libc_deps(portdb: portage.dbapi.porttree.dbapi, realized: bool = False):
+    """Finds libc package for a ROOT via portdb.
+
+    Parameters
+    ----------
+    portdb : dbapi
+        dbapi instance for portdb (for installed packages).
+    realized : bool
+        Request installed atoms rather than the installed package satisfying LIBC_PACKAGE_ATOM.
+
+    Returns
+    -------
+    list
+        List of libc packages (or atoms if realized is passed).
+    """
+
+    libc_pkgs = set()
+
+    for atom in expand_new_virt(
+        portdb,
+        LIBC_PACKAGE_ATOM,
+    ):
+        if atom.blocker:
+            continue
+
+        if not realized:
+            # Just the raw packages were requested (whatever satifies the virtual)
+            libc_pkgs.add(atom)
+            continue
+
+        # This will give us something like sys-libs/glibc:2.2, but we want to know
+        # what installed atom actually satifies that.
+        try:
+            libc_pkgs.add(portdb.match(atom)[0])
+        except IndexError:
+            continue
+
+    return libc_pkgs
+
+
+def strip_libc_deps(dep_struct: list, libc_deps: set):
+    """Strip libc dependency out of a given dependency strucutre.
+
+    Parameters
+    ----------
+    dep_struct: list
+        List of package dependencies (atoms).
+
+    libc_deps: set
+        List of dependencies satisfying LIBC_PACKAGE_ATOM to be
+        stripped out of any dependencies.
+
+    Returns
+    -------
+    list
+        List of dependencies with any matching libc_deps removed.
+    """
+    # We're going to just grab the libc provider for ROOT and
+    # strip out any dep for the purposes of --changed-deps.
+    # We can't go off versions, even though it'd be more precise
+    # (see below), because we'd end up with FPs and unnecessary
+    # --changed-deps results far too often.
+    #
+    # This penalizes a bit the case where someone adds a
+    # minimum (or maximum) version of libc explicitly in an ebuild
+    # without a new revision, but that's extremely rare, and doesn't
+    # feel like it changes the balance for what we prefer here.
+
+    for i, x in reversed(list(enumerate(dep_struct))):
+        # We only need to bother if x is an Atom because we know the deps
+        # we inject are simple & flat.
+        if isinstance(x, Atom) and any(x.cp == libc_dep.cp for libc_dep in libc_deps):
+            del dep_struct[i]