gdbsupport: change xml_escape_text_append's parameter from pointer to reference

The passed in string can't be nullptr, it makes more sense to pass in a
reference.

Change-Id: Idc8bd38abe1d6d9b44aa227d7856956848c233b3

gdb/unittests/xml-utils-selftests.c

@@ -40,7 +40,7 @@ static void test_xml_escape_text_append ()
   const char *input = "<this isn't=\"xml\"> &";
   const char *expected_output
     = "foo<xml>&lt;this isn&apos;t=&quot;xml&quot;&gt; &amp;";
-  xml_escape_text_append (&actual_output, input);
+  xml_escape_text_append (actual_output, input);
 
   SELF_CHECK (actual_output == expected_output);
 }

gdbserver/linux-low.cc

@@ -6520,7 +6520,7 @@ read_link_map (std::string &document, CORE_ADDR lmid, CORE_ADDR lm_addr,
       if (libname[0] != '\0')
 	{
 	  string_appendf (document, "<library name=\"");
-	  xml_escape_text_append (&document, (char *) libname);
+	  xml_escape_text_append (document, (char *) libname);
 	  string_appendf (document, "\" lm=\"0x%s\" l_addr=\"0x%s\" "
 			  "l_ld=\"0x%s\" lmid=\"0x%s\"/>",
 			  paddress (lm_addr), paddress (l_addr),

gdbserver/netbsd-low.cc

@@ -1086,7 +1086,7 @@ netbsd_qxfer_libraries_svr4 (const pid_t pid, const char *annex,
 		}
 
 	      string_appendf (document, "<library name=\"");
-	      xml_escape_text_append (&document, (char *) libname);
+	      xml_escape_text_append (document, (char *) libname);
 	      string_appendf (document, "\" lm=\"0x%lx\" "
 			      "l_addr=\"0x%lx\" l_ld=\"0x%lx\"/>",
 			      (unsigned long) lm_addr, (unsigned long) l_addr,

gdbsupport/xml-utils.cc

@@ -27,7 +27,7 @@ xml_escape_text (const char *text)
 {
   std::string result;
 
-  xml_escape_text_append (&result, text);
+  xml_escape_text_append (result, text);
 
   return result;
 }
@@ -35,29 +35,29 @@ xml_escape_text (const char *text)
 /* See xml-utils.h.  */
 
 void
-xml_escape_text_append (std::string *result, const char *text)
+xml_escape_text_append (std::string &result, const char *text)
 {
   /* Expand the result.  */
   for (int i = 0; text[i] != '\0'; i++)
     switch (text[i])
       {
       case '\'':
-	*result += "'";
+	result += "'";
 	break;
       case '\"':
-	*result += """;
+	result += """;
 	break;
       case '&':
-	*result += "&";
+	result += "&";
 	break;
       case '<':
-	*result += "&lt;";
+	result += "&lt;";
 	break;
       case '>':
-	*result += "&gt;";
+	result += "&gt;";
 	break;
       default:
-	*result += text[i];
+	result += text[i];
 	break;
       }
 }

gdbsupport/xml-utils.h

@@ -28,6 +28,6 @@ extern std::string xml_escape_text (const char *text);
 /* Append TEXT to RESULT, with special characters replaced by entity
    references.  */
 
-extern void xml_escape_text_append (std::string *result, const char *text);
+extern void xml_escape_text_append (std::string &result, const char *text);
 
 #endif /* COMMON_XML_UTILS_H */