Fix EXSLT functions returning RVTs from outer scopes

The RVTs referenced from function results must not be blindly registered
as local, as they might be part of variables from an outer scope. Remove
LOCAL/VARIABLE distinction for RVTs. Don't register as local RVT
unconditionally when reflagging as LOCAL. Instead, register function
result RVTs from inner variables as local RVTs when they're released in
xsltFreeStackElem. Keep local function result RVTs xsltReleaseLocalRVTs
instead of reregistering.

Closes: https://gitlab.gnome.org/GNOME/libxslt/issues/2

Thanks to Daniel Mendler and Martin Gieseking for the reports.

libexslt/functions.c

@@ -426,7 +426,15 @@ exsltFuncFunctionFunction (xmlXPathParserContextPtr ctxt, int nargs) {
 	}
     }
     /*
-     * actual processing
+     * Actual processing. Note that contextVariable is set to NULL which
+     * means that RVTs returned from functions always end up as local RVTs,
+     * not as variable fragments if the function is called in the select
+     * expression of an xsl:variable. This is a hack that only works because
+     * xsltReleaseLocalRVTs isn't called after processing xsl:variable.
+     *
+     * It would probably be better to remove the fragile contextVariable
+     * logic and make xsltEvalVariable move the required RVTs into the
+     * variable manually.
      */
     fake = xmlNewDocNode(tctxt->output, NULL,
 			 (const xmlChar *)"fake", NULL);
@@ -766,6 +774,7 @@ exsltFuncResultElem (xsltTransformContextPtr ctxt,
 	    return;
 	}
         /* Mark as function result. */
+        xsltRegisterLocalRVT(ctxt, container);
         container->psvi = XSLT_RVT_FUNC_RESULT;
 
 	oldInsert = ctxt->insert;

libxslt/transform.c

@@ -2295,6 +2295,7 @@ static void
 xsltReleaseLocalRVTs(xsltTransformContextPtr ctxt, xmlDocPtr base)
 {
     xmlDocPtr cur = ctxt->localRVT, tmp;
+    xmlDocPtr prev = NULL;
 
     if (cur == base)
         return;
@@ -2308,16 +2309,26 @@ xsltReleaseLocalRVTs(xsltTransformContextPtr ctxt, xmlDocPtr base)
             xsltReleaseRVT(ctxt, tmp);
         } else if (tmp->psvi == XSLT_RVT_GLOBAL) {
             xsltRegisterPersistRVT(ctxt, tmp);
-        } else if (tmp->psvi != XSLT_RVT_FUNC_RESULT) {
+        } else if (tmp->psvi == XSLT_RVT_FUNC_RESULT) {
+            if (prev == NULL)
+                ctxt->localRVT = tmp;
+            else
+                prev->next = (xmlNodePtr) tmp;
+            tmp->prev = (xmlNodePtr) prev;
+            prev = tmp;
+        } else {
             xmlGenericError(xmlGenericErrorContext,
                     "xsltReleaseLocalRVTs: Unexpected RVT flag %p\n",
                     tmp->psvi);
         }
     } while (cur != base);
 
+    if (prev == NULL)
+        ctxt->localRVT = base;
+    else
+        prev->next = (xmlNodePtr) base;
     if (base != NULL)
-        base->prev = NULL;
+        base->prev = (xmlNodePtr) prev;
-    ctxt->localRVT = base;
 }
 
 /**

libxslt/variables.c

@@ -123,7 +123,7 @@ xsltRegisterTmpRVT(xsltTransformContextPtr ctxt, xmlDocPtr RVT)
 	return(-1);
 
     RVT->prev = NULL;
-    RVT->psvi = XSLT_RVT_VARIABLE;
+    RVT->psvi = XSLT_RVT_LOCAL;
 
     /*
     * We'll restrict the lifetime of user-created fragments
@@ -163,6 +163,7 @@ xsltRegisterLocalRVT(xsltTransformContextPtr ctxt,
 	return(-1);
 
     RVT->prev = NULL;
+    RVT->psvi = XSLT_RVT_LOCAL;
 
     /*
     * When evaluating "select" expressions of xsl:variable
@@ -173,7 +174,6 @@ xsltRegisterLocalRVT(xsltTransformContextPtr ctxt,
     if ((ctxt->contextVariable != NULL) &&
 	(XSLT_TCTXT_VARIABLE(ctxt)->flags & XSLT_VAR_IN_SELECT))
     {
-        RVT->psvi = XSLT_RVT_VARIABLE;
 	RVT->next = (xmlNodePtr) XSLT_TCTXT_VARIABLE(ctxt)->fragment;
 	XSLT_TCTXT_VARIABLE(ctxt)->fragment = RVT;
 	return(0);
@@ -183,7 +183,6 @@ xsltRegisterLocalRVT(xsltTransformContextPtr ctxt,
     * If not reference by a returning instruction (like EXSLT's function),
     * then this fragment will be freed, when the instruction exits.
     */
-    RVT->psvi = XSLT_RVT_LOCAL;
     RVT->next = (xmlNodePtr) ctxt->localRVT;
     if (ctxt->localRVT != NULL)
 	ctxt->localRVT->prev = (xmlNodePtr) RVT;
@@ -314,14 +313,8 @@ xsltFlagRVTs(xsltTransformContextPtr ctxt, xmlXPathObjectPtr obj, void *val) {
 #endif
 
             if (val == XSLT_RVT_LOCAL) {
-                if (doc->psvi != XSLT_RVT_FUNC_RESULT) {
+                if (doc->psvi == XSLT_RVT_FUNC_RESULT)
-		    xmlGenericError(xmlGenericErrorContext,
+                    doc->psvi = XSLT_RVT_LOCAL;
-                            "xsltFlagRVTs: Invalid transition %p => LOCAL\n",
-                            doc->psvi);
-                    return(-1);
-                }
-
-                xsltRegisterLocalRVT(ctxt, doc);
             } else if (val == XSLT_RVT_GLOBAL) {
                 if (doc->psvi != XSLT_RVT_LOCAL) {
 		    xmlGenericError(xmlGenericErrorContext,
@@ -585,10 +578,12 @@ xsltFreeStackElem(xsltStackElemPtr elem) {
 	    cur = elem->fragment;
 	    elem->fragment = (xmlDocPtr) cur->next;
 
-            if (cur->psvi == XSLT_RVT_VARIABLE) {
+            if (cur->psvi == XSLT_RVT_LOCAL) {
-		xsltReleaseRVT((xsltTransformContextPtr) elem->context,
+		xsltReleaseRVT(elem->context, cur);
-		    cur);
+            } else if (cur->psvi == XSLT_RVT_FUNC_RESULT) {
-            } else if (cur->psvi != XSLT_RVT_FUNC_RESULT) {
+                xsltRegisterLocalRVT(elem->context, cur);
+                cur->psvi = XSLT_RVT_FUNC_RESULT;
+            } else {
                 xmlGenericError(xmlGenericErrorContext,
                         "xsltFreeStackElem: Unexpected RVT flag %p\n",
                         cur->psvi);
@@ -992,7 +987,7 @@ xsltEvalVariable(xsltTransformContextPtr ctxt, xsltStackElemPtr variable,
 		* the Result Tree Fragment.
 		*/
 		variable->fragment = container;
-                container->psvi = XSLT_RVT_VARIABLE;
+                container->psvi = XSLT_RVT_LOCAL;
 
 		oldOutput = ctxt->output;
 		oldInsert = ctxt->insert;

libxslt/variables.h

@@ -45,14 +45,6 @@ extern "C" {
  */
 #define XSLT_RVT_LOCAL       ((void *)1)
 
-/**
- * XSLT_RVT_VARIABLE:
- *
- * RVT is part of a local variable and destroyed after the variable goes out
- * of scope.
- */
-#define XSLT_RVT_VARIABLE    ((void *)2)
-
 /**
  * XSLT_RVT_FUNC_RESULT:
  *
@@ -60,14 +52,14 @@ extern "C" {
  * destroyed after exiting a template and will be reset to XSLT_RVT_LOCAL or
  * XSLT_RVT_VARIABLE in the template that receives the return value.
  */
-#define XSLT_RVT_FUNC_RESULT ((void *)3)
+#define XSLT_RVT_FUNC_RESULT ((void *)2)
 
 /**
  * XSLT_RVT_GLOBAL:
  *
  * RVT is part of a global variable.
  */
-#define XSLT_RVT_GLOBAL      ((void *)4)
+#define XSLT_RVT_GLOBAL      ((void *)3)
 
 /*
  * Interfaces for the variable module.

tests/docs/bug-210.xml

@@ -0,0 +1 @@
+<doc/>

tests/docs/bug-211.xml

@@ -0,0 +1 @@
+<doc/>

tests/general/bug-210.out

@@ -0,0 +1,2 @@
+<?xml version="1.0"?>
+<var>value</var>

tests/general/bug-210.xsl

@@ -0,0 +1,20 @@
+<xsl:stylesheet version="1.0"
+    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+    xmlns:exsl="http://exslt.org/common"
+    xmlns:func="http://exslt.org/functions"
+    xmlns:my="my-namespace"
+    extension-element-prefixes="exsl func">
+
+<xsl:template match="/">
+    <xsl:variable name="var">
+        <var>value</var>
+    </xsl:variable>
+    <xsl:copy-of select="my:func($var)"/>
+</xsl:template>
+
+<func:function name="my:func">
+    <xsl:param name="var"/>
+    <func:result select="$var"/>
+</func:function>
+
+</xsl:stylesheet>

tests/general/bug-211.out

@@ -0,0 +1,2 @@
+<?xml version="1.0"?>
+__

tests/general/bug-211.xsl

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<xsl:stylesheet version="1.0"
+                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+                xmlns:str="http://exslt.org/strings"
+                xmlns:fn="http://exslt.org/functions"
+                xmlns:adoc="http://asciidoc.org/"
+                extension-element-prefixes="fn">
+
+  <fn:function name="adoc:sanitize">
+    <xsl:param name="id"/>
+    <xsl:variable name="tmp" select="str:replace($id, '__', '_')"/>
+    <xsl:choose>
+      <xsl:when test="contains($tmp, '__')">
+        <fn:result select="adoc:sanitize($tmp)"/>
+      </xsl:when>
+      <xsl:otherwise>
+        <fn:result select="$id"/>
+      </xsl:otherwise>
+    </xsl:choose>
+  </fn:function>
+
+  <xsl:template match="*">
+    <xsl:value-of select="adoc:sanitize('________')"/>
+  </xsl:template>
+
+</xsl:stylesheet>