From 3ab0c9df69917e2948e1341fa640f39b49a47db5 Mon Sep 17 00:00:00 2001
From: Mike Dalessio <mike.dalessio@gmail.com>
Date: Sat, 12 Jan 2019 17:43:57 -0500
Subject: [PATCH] ensure we trap XML errors while applying XSLT stylesheet

otherwise trivial XML errors will silently result in NULL being
returned by xsltApplyStylesheet() and a subsequent segfault

Fixes #1802
---
 ext/nokogiri/xslt_stylesheet.c |  2 +-
 test/test_xslt_transforms.rb   | 47 ++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/ext/nokogiri/xslt_stylesheet.c b/ext/nokogiri/xslt_stylesheet.c
index d0ad6eaaf1..e98302eb07 100644
--- a/ext/nokogiri/xslt_stylesheet.c
+++ b/ext/nokogiri/xslt_stylesheet.c
@@ -165,7 +165,7 @@ static VALUE transform(int argc, VALUE* argv, VALUE self)
 
     errstr = rb_str_new(0, 0);
     xsltSetGenericErrorFunc((void *)errstr, xslt_generic_error_handler);
-    xmlSetGenericErrorFunc(NULL, (xmlGenericErrorFunc)&swallow_superfluous_xml_errors);
+    xmlSetGenericErrorFunc((void *)errstr, xslt_generic_error_handler);
 
     result = xsltApplyStylesheet(wrapper->ss, xml, params);
     free(params);
diff --git a/test/test_xslt_transforms.rb b/test/test_xslt_transforms.rb
index 1be9b7ed80..3b06e7f0d3 100644
--- a/test/test_xslt_transforms.rb
+++ b/test/test_xslt_transforms.rb
@@ -311,4 +311,51 @@ def test_non_html_xslt_transform
     result = xsl.transform xml
     assert !result.html?
   end
+
+  it "should not crash when given XPath 2.0 features" do
+    #
+    #  https://github.com/sparklemotion/nokogiri/issues/1802
+    #
+    #  note that here the XPath 2.0 feature is `decimal`.
+    #  this test case is taken from the example provided in the original issue.
+    #
+    xml = <<~EOXML
+        <?xml version="1.0" encoding="UTF-8"?>
+        <Invoice xmlns="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2"
+                 xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2"
+                 xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2"
+                 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+                 xsi:schemaLocation="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2">
+          <cac:TaxTotal>
+            <cbc:TaxAmount currencyID="EUR">48.00</cbc:TaxAmount>
+          </cac:TaxTotal>
+        </Invoice>
+      EOXML
+
+    xsl = <<~EOXSL
+        <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+        <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+                        xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2"
+                        xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2"
+                        xmlns:ubl="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2"
+                        xmlns:xs="http://www.w3.org/2001/XMLSchema"
+                        version="1.0">
+          <xsl:template match="/">
+            <xsl:apply-templates select="/" mode="qwerty"/>
+          </xsl:template>
+          <xsl:template match="/ubl:Invoice/cac:TaxTotal" priority="1001" mode="qwerty">
+            <xsl:choose>
+              <xsl:when test="(round(xs:decimal(child::cbc:TaxAmount)))"/>
+            </xsl:choose>
+          </xsl:template>
+        </xsl:stylesheet>
+      EOXSL
+
+    doc = Nokogiri::XML(xml)
+    xslt = Nokogiri::XSLT(xsl)
+    exception = assert_raise(RuntimeError) do
+      xslt.transform(doc)
+    end
+    assert_match(/decimal/, exception.message)
+  end
 end