From: Matthew Fernandez <matthew.fernandez@gmail.com>
Date: Sun, 8 Nov 2020 22:56:27 +0000 (-0800)
Subject: fix: anticipate no non-normal edges when computing direction with concentrate
X-Git-Tag: 2.46.0~12^2~2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=84e468e775e1d1b293624f1c8e70c226eb4a6e41;p=graphviz

fix: anticipate no non-normal edges when computing direction with concentrate

With concentrate enabled (`concentrate=true`), the direction of edges is
analyzed in lib/dotgen/conc.c. The loops in `samedir()` did not anticipate that
they may not find a single non-normal edge before hitting the end of an edge
chain. This change removes this assumption.

Fixes #167, #1771.
---

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ca70fc6e9..db845ee95 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -67,6 +67,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - sfdp craches #236
 - fdp segmentation fault with GK=0 #1290
 - fdp crash #1865
+- Graphviz always crash with this simple dot file #167
+- Seg fault in dot #1771
 
 ## [2.44.1] - 2020-06-29
 
diff --git a/lib/dotgen/conc.c b/lib/dotgen/conc.c
index 136a15744..e2be813b1 100644
--- a/lib/dotgen/conc.c
+++ b/lib/dotgen/conc.c
@@ -28,8 +28,12 @@ static boolean samedir(edge_t * e, edge_t * f)
 {
     edge_t *e0, *f0;
 
-    for (e0 = e; ED_edge_type(e0) != NORMAL; e0 = ED_to_orig(e0));
-    for (f0 = f; ED_edge_type(f0) != NORMAL; f0 = ED_to_orig(f0));
+    for (e0 = e; e0 != NULL && ED_edge_type(e0) != NORMAL; e0 = ED_to_orig(e0));
+    if (e0 == NULL)
+	return FALSE;
+    for (f0 = f; f0 != NULL && ED_edge_type(f0) != NORMAL; f0 = ED_to_orig(f0));
+    if (f0 == NULL)
+	return FALSE;
     if (ED_conc_opp_flag(e0))
 	return FALSE;
     if (ED_conc_opp_flag(f0))
diff --git a/rtest/167.dot b/rtest/167.dot
new file mode 100644
index 000000000..46a5d8f6b
--- /dev/null
+++ b/rtest/167.dot
@@ -0,0 +1,8 @@
+digraph G {
+ concentrate=true;
+  a -> 4 -> b
+  a -> b
+  a -> b
+  b -> a
+}
+
diff --git a/rtest/test_regression.py b/rtest/test_regression.py
index 1daf11944..62c9f211f 100644
--- a/rtest/test_regression.py
+++ b/rtest/test_regression.py
@@ -103,6 +103,22 @@ def test_165_3():
     assert any(r'hello \\\" world' in l for l in ldraw), \
       'unexpected ldraw contents'
 
+def test_167():
+    '''
+    using concentrate=true should not result in a segfault
+    https://gitlab.com/graphviz/graphviz/-/issues/167
+    '''
+
+    # locate our associated test case in this directory
+    input = os.path.join(os.path.dirname(__file__), '167.dot')
+    assert os.path.exists(input), 'unexpectedly missing test case'
+
+    # process this with dot
+    ret = subprocess.call(['dot', '-Tpdf', '-o', os.devnull, input])
+
+    # Graphviz should not have caused a segfault
+    assert ret != -signal.SIGSEGV, 'Graphviz segfaulted'
+
 def test_793():
     '''
     Graphviz should not crash when using VRML output with a non-writable current