[libxslt] Initialize ctxt->output before evaluating global vars

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 99eb3e4358c93984de7597f6fdc8bb64973046c5
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Mon Feb 11 23:29:53 2019 +0100

    Initialize ctxt->output before evaluating global vars
    
    Otherwise, an xsl:element in an EXSLT function could lead to a null
    pointer dereference. Also initialize some other variables earlier.
    
    Fixes #10.

 libxslt/transform.c       | 13 +++++++------
 tests/docs/bug-215.xml    |  1 +
 tests/general/bug-215.err |  8 ++++++++
 tests/general/bug-215.out |  0
 tests/general/bug-215.xsl |  6 ++++++
 5 files changed, 22 insertions(+), 6 deletions(-)
---
diff --git a/libxslt/transform.c b/libxslt/transform.c
index ed5afacb..13793914 100644
--- a/libxslt/transform.c
+++ b/libxslt/transform.c
@@ -6011,6 +6011,13 @@ xsltApplyStylesheetInternal(xsltStylesheetPtr style, xmlDocPtr doc,
         res->encoding = xmlStrdup(encoding);
     variables = style->variables;
 
+    ctxt->node = (xmlNodePtr) doc;
+    ctxt->output = res;
+
+    ctxt->xpathCtxt->contextSize = 1;
+    ctxt->xpathCtxt->proximityPosition = 1;
+    ctxt->xpathCtxt->node = NULL; /* TODO: Set the context node here? */
+
     /*
      * Start the evaluation, evaluate the params, the stylesheets globals
      * and start by processing the top node.
@@ -6020,7 +6027,6 @@ xsltApplyStylesheetInternal(xsltStylesheetPtr style, xmlDocPtr doc,
     /*
     * Evaluate global params and user-provided params.
     */
-    ctxt->node = (xmlNodePtr) doc;
     if (ctxt->globalVars == NULL)
        ctxt->globalVars = xmlHashCreate(20);
     if (params != NULL) {
@@ -6035,14 +6041,9 @@ xsltApplyStylesheetInternal(xsltStylesheetPtr style, xmlDocPtr doc,
     /* Clean up any unused RVTs. */
     xsltReleaseLocalRVTs(ctxt, NULL);
 
-    ctxt->node = (xmlNodePtr) doc;
-    ctxt->output = res;
     ctxt->insert = (xmlNodePtr) res;
     ctxt->varsBase = ctxt->varsNr - 1;
 
-    ctxt->xpathCtxt->contextSize = 1;
-    ctxt->xpathCtxt->proximityPosition = 1;
-    ctxt->xpathCtxt->node = NULL; /* TODO: Set the context node here? */
     /*
     * Start processing the source tree -----------------------------------
     */
diff --git a/tests/docs/bug-215.xml b/tests/docs/bug-215.xml
new file mode 100644
index 00000000..ead3414d
--- /dev/null
+++ b/tests/docs/bug-215.xml
@@ -0,0 +1 @@
+<empty/>
diff --git a/tests/general/bug-215.err b/tests/general/bug-215.err
new file mode 100644
index 00000000..a4fbd23d
--- /dev/null
+++ b/tests/general/bug-215.err
@@ -0,0 +1,8 @@
+  ELEMENT fake
+element fake: error : Node has no parent
+    ELEMENT elem
+{DEF}f: cannot write to result tree while executing a function
+xmlXPathCompiledEval: No result on the stack.
+runtime error: file ./bug-215.xsl line 5 element variable
+Evaluating global variable  var/param being computed failed
+no result for ./../docs/bug-215.xml
diff --git a/tests/general/bug-215.out b/tests/general/bug-215.out
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/general/bug-215.xsl b/tests/general/bug-215.xsl
new file mode 100644
index 00000000..0dabaaae
--- /dev/null
+++ b/tests/general/bug-215.xsl
@@ -0,0 +1,6 @@
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; xmlns:func="http://exslt.org/functions"; 
xmlns:abc="DEF" version="1.0" extension-element-prefixes="func">
+  <func:function name="abc:f">
+    <xsl:element name="elem"/>
+  </func:function>
+  <xsl:variable name="v" select="abc:f()"/>
+</xsl:stylesheet>