File 0912-digraph-Avoid-false-edges-for-vertices-with-names-co.patch of Package erlang
From c5e3d13f0325f8caa155bb7cb7298e749b594d50 Mon Sep 17 00:00:00 2001
From: Frej Drejhammar <frej@sics.se>
Date: Wed, 6 May 2020 06:34:45 +0200
Subject: [PATCH] digraph: Avoid false edges for vertices with names containing
a '_'
This patch fixes a bug in the digraph module where in_edges/2 and
out_edges/2 return false edges in the case they are called for a
vertex which has a '_' in its name term. The following example shows
the problem:
G = new([acyclic]),
A = add_vertex(G, 'A'),
B = add_vertex(G, '_'),
AB = add_edge(G, A, B),
0 = out_degree(G, B), %% ok
[] = out_edges(G, B), %% Fails as [AB] is returned
An edge, E, emanating from and incident on a vertex is stored in the
ntab-ets table as a record of the form {{out, V}, E} and {{in, V}, E}
respectively. As out_edges/2 and in_edges/2 use ets:select/2 to look
up the relevant edges, a vertex with a '_' somewhere in the term used
as its name will trigger ets to do a wildcard match. In the example
above, this will return all out-edges in the whole graph. This problem
is fixed by switching from ets:select to ets:lookup.
This patch includes an extended test case which checks the correctness
of the fix described above as well as checking that the other
edge-related functions in digraph do not suffer from the same problem.
---
lib/stdlib/src/digraph.erl | 4 +--
lib/stdlib/test/digraph_SUITE.erl | 51 +++++++++++++++++++++++++++++--
2 files changed, 50 insertions(+), 5 deletions(-)
diff --git a/lib/stdlib/src/digraph.erl b/lib/stdlib/src/digraph.erl
index 8a4df95027..58d493cf54 100644
--- a/lib/stdlib/src/digraph.erl
+++ b/lib/stdlib/src/digraph.erl
@@ -230,7 +230,7 @@ in_neighbours(G, V) ->
Edges :: [edge()].
in_edges(G, V) ->
- ets:select(G#digraph.ntab, [{{{in, V}, '$1'}, [], ['$1']}]).
+ [E || {{in, _}, E} <- ets:lookup(G#digraph.ntab, {in, V})].
-spec out_degree(G, V) -> non_neg_integer() when
G :: graph(),
@@ -255,7 +255,7 @@ out_neighbours(G, V) ->
Edges :: [edge()].
out_edges(G, V) ->
- ets:select(G#digraph.ntab, [{{{out, V}, '$1'}, [], ['$1']}]).
+ [E || {{out, _}, E} <- ets:lookup(G#digraph.ntab, {out, V})].
-spec add_edge(G, V1, V2) -> edge() | {'error', add_edge_err_rsn()} when
G :: graph(),
diff --git a/lib/stdlib/test/digraph_SUITE.erl b/lib/stdlib/test/digraph_SUITE.erl
index b5d3452616..ce0bc90f1c 100644
--- a/lib/stdlib/test/digraph_SUITE.erl
+++ b/lib/stdlib/test/digraph_SUITE.erl
@@ -31,7 +31,7 @@
init_per_group/2,end_per_group/2]).
-export([opts/1, degree/1, path/1, cycle/1, vertices/1,
- edges/1, data/1, otp_3522/1, otp_3630/1, otp_8066/1]).
+ edges/1, data/1, otp_3522/1, otp_3630/1, otp_8066/1, vertex_names/1]).
-export([spawn_graph/2]).
@@ -41,10 +41,10 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
all() ->
[opts, degree, path, cycle, {group, misc},
- {group, tickets}].
+ {group, tickets}, vertex_names].
groups() ->
- [{misc, [], [vertices, edges, data]},
+ [{misc, [], [vertices, edges, data, vertex_names]},
{tickets, [], [otp_3522, otp_3630, otp_8066]}].
init_per_suite(Config) ->
@@ -337,6 +337,51 @@ otp_8066(Config) when is_list(Config) ->
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+vertex_names(Config) when is_list(Config) ->
+ %% Check that a node named '_' does not lead to wildcard matches
+ %% in ets.
+
+ G = digraph:new([acyclic]),
+ A = digraph:add_vertex(G, 'A'),
+ B = digraph:add_vertex(G, '_'),
+ AB = digraph:add_edge(G, A, B),
+
+ %% Link A -> B
+ 1 = digraph:out_degree(G, A),
+ 1 = digraph:in_degree(G, B),
+ 0 = digraph:out_degree(G, B),
+ 0 = digraph:in_degree(G, A),
+ [B] = digraph:out_neighbours(G, A),
+ [A] = digraph:in_neighbours(G, B),
+ [] = digraph:out_neighbours(G, B),
+ [] = digraph:in_neighbours(G, A),
+ [AB] = digraph:out_edges(G, A),
+ [AB] = digraph:in_edges(G, B),
+ [] = digraph:out_edges(G, B),
+ [] = digraph:in_edges(G, A),
+
+ %% Reverse the edge
+ digraph:del_edge(G, AB),
+ BA = digraph:add_edge(G, B, A),
+
+ 1 = digraph:out_degree(G, B),
+ 1 = digraph:in_degree(G, A),
+ 0 = digraph:out_degree(G, A),
+ 0 = digraph:in_degree(G, B),
+ [A] = digraph:out_neighbours(G, B),
+ [B] = digraph:in_neighbours(G, A),
+ [] = digraph:out_neighbours(G, A),
+ [] = digraph:in_neighbours(G, B),
+ [BA] = digraph:out_edges(G, B),
+ [BA] = digraph:in_edges(G, A),
+ [] = digraph:out_edges(G, A),
+ [] = digraph:in_edges(G, B),
+
+ digraph:delete(G),
+ ok.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
sane(G) ->
sane1(G),
erase(sane) =:= undefined.
--
2.26.1
