diff --git a/builtin.cpp b/builtin.cpp
index c5f52a2f5..9a3b4776b 100644
--- a/builtin.cpp
+++ b/builtin.cpp
@@ -2145,7 +2145,7 @@ static int builtin_read( parser_t &parser, wchar_t **argv )
 	*/
 	if( isatty(0) && builtin_stdin == 0 )
 	{
-		wchar_t *line;
+		const wchar_t *line;
 		
 		reader_push( mode_name );
 		reader_set_prompt( prompt );
diff --git a/builtin_commandline.cpp b/builtin_commandline.cpp
index 0ead09949..f45c9f290 100644
--- a/builtin_commandline.cpp
+++ b/builtin_commandline.cpp
@@ -56,7 +56,7 @@ enum
    Pointer to what the commandline builtin considers to be the current
    contents of the command line buffer.
  */
-static wchar_t *current_buffer=0;
+static const wchar_t *current_buffer=0;
 /**
    What the commandline builtin considers to be the current cursor
    position.
@@ -66,7 +66,7 @@ static int current_cursor_pos = -1;
 /**
    Returns the current commandline buffer.
 */
-static wchar_t *get_buffer()
+static const wchar_t *get_buffer()
 {
 	return current_buffer;
 }
@@ -230,7 +230,7 @@ static int builtin_commandline( parser_t &parser, wchar_t **argv )
 	int cursor_mode = 0;
 	int line_mode = 0;
 	int search_mode = 0;
-	wchar_t *begin, *end;
+	const wchar_t *begin, *end;
 
 	current_buffer = (wchar_t *)builtin_complete_get_temporary_buffer();
 	if( current_buffer )
@@ -575,7 +575,7 @@ static int builtin_commandline( parser_t &parser, wchar_t **argv )
 	if( line_mode )
 	{
 		int pos = reader_get_cursor_pos();
-		wchar_t *buff = reader_get_buffer();
+		const wchar_t *buff = reader_get_buffer();
 		sb_printf( sb_out, L"%d\n", parse_util_lineno( buff, pos ) );
 		return 0;
 			
diff --git a/builtin_complete.cpp b/builtin_complete.cpp
index 198b369a6..5ea10487c 100644
--- a/builtin_complete.cpp
+++ b/builtin_complete.cpp
@@ -303,7 +303,7 @@ static int builtin_complete( parser_t &parser, wchar_t **argv )
 	array_list_t gnu_opt, old_opt;
 	const wchar_t *comp=L"", *desc=L"", *condition=L"";
 
-	wchar_t *do_complete = 0;
+	const wchar_t *do_complete = 0;
 	
 	array_list_t cmd;
 	array_list_t path;
@@ -545,7 +545,7 @@ static int builtin_complete( parser_t &parser, wchar_t **argv )
 
 			const wchar_t *prev_temporary_buffer = temporary_buffer;
 
-			wchar_t *token;
+			const wchar_t *token;
 
 			parse_util_token_extent( do_complete, wcslen( do_complete ), &token, 0, 0, 0 );
 						
diff --git a/complete.cpp b/complete.cpp
index f9c0797c0..ae7e6fef2 100644
--- a/complete.cpp
+++ b/complete.cpp
@@ -1543,11 +1543,11 @@ static int complete_param( const wchar_t *cmd_orig,
 /**
    Perform file completion on the specified string
 */
-static void complete_param_expand( wchar_t *str,
+static void complete_param_expand( const wchar_t *str,
 								   std::vector<completion_t> &comp_out,
 								   int do_file )
 {
-	wchar_t *comp_str;
+	const wchar_t *comp_str;
 	int flags;
 	
 	if( (wcsncmp( str, L"--", 2 )) == 0 && (comp_str = wcschr(str, L'=' ) ) )
@@ -1758,10 +1758,10 @@ static int try_complete_user( const wchar_t *cmd,
 void complete( const wchar_t *cmd,
 			   std::vector<completion_t> &comp )
 {
-	wchar_t *tok_begin, *tok_end, *cmdsubst_begin, *cmdsubst_end, *prev_begin, *prev_end;
+	const wchar_t *tok_begin, *tok_end, *cmdsubst_begin, *cmdsubst_end, *prev_begin, *prev_end;
 	wchar_t *buff;
 	tokenizer tok;
-	wchar_t *current_token=0, *current_command=0, *prev_token=0;
+	const wchar_t *current_token=0, *current_command=0, *prev_token=0;
 	int on_command=0;
 	int pos;
 	int done=0;
@@ -1854,7 +1854,7 @@ void complete( const wchar_t *cmd,
 						{
 							int token_end;
 							
-							free( current_command );
+							free( (void *)current_command );
 							current_command = wcsdup( ncmd );
 							
 							token_end = tok_get_pos( &tok ) + wcslen( ncmd );
@@ -1928,7 +1928,7 @@ void complete( const wchar_t *cmd,
 			(current_token[0] == L'-') && 
 			!(use_command && use_function && use_builtin ) )
 		{
-			free( current_command );
+			free( (void *)current_command );
 			if( use_command == 0 )
 				current_command = wcsdup( L"builtin" );
 			else
@@ -2009,9 +2009,9 @@ void complete( const wchar_t *cmd,
 		}
 	}
 	
-	free( current_token );
-	free( current_command );
-	free( prev_token );
+	free( (void *)current_token );
+	free( (void *)current_command );
+	free( (void *)prev_token );
 
 	condition_cache_clear();
 
diff --git a/env.cpp b/env.cpp
index 56bbcf402..b5989e7cd 100644
--- a/env.cpp
+++ b/env.cpp
@@ -1143,7 +1143,7 @@ env_var_t env_get_string( const wchar_t *key )
 	if( wcscmp( key, L"history" ) == 0 )
 	{
         wcstring result;
-		wchar_t *current;
+		const wchar_t *current;
 		int i;		
 		int add_current=0;
 		
@@ -1251,7 +1251,7 @@ const wchar_t *env_get( const wchar_t *key )
 
 	if( wcscmp( key, L"history" ) == 0 )
 	{
-		wchar_t *current;
+		const wchar_t *current;
 		dyn_var.clear();
 		
 		current = reader_get_buffer();
diff --git a/highlight.cpp b/highlight.cpp
index 5d6173b5b..edd977a40 100644
--- a/highlight.cpp
+++ b/highlight.cpp
@@ -992,8 +992,7 @@ void highlight_shell( const wchar_t *buff, int *color, int pos, array_list_t *er
 	if( pos >= 0 && pos <= len )
 	{
 		
-		wchar_t *tok_begin, *tok_end;
-		wchar_t *token;
+		const wchar_t *tok_begin, *tok_end, *token;
 		
 		parse_util_token_extent( buff, pos, &tok_begin, &tok_end, 0, 0 );
 		if( tok_begin && tok_end )
diff --git a/parse_util.cpp b/parse_util.cpp
index 759c50e40..795b4c536 100644
--- a/parse_util.cpp
+++ b/parse_util.cpp
@@ -109,10 +109,10 @@ int parse_util_lineno( const wchar_t *str, int len )
 }
 
 
-int parse_util_get_line_from_offset( wchar_t *buff, int pos )
+int parse_util_get_line_from_offset( const wcstring &str, int pos )
 {
 	//	return parse_util_lineno( buff, pos );
-
+    const wchar_t *buff = str.c_str();
 	int i;
 	int count = 0;
 	if( pos < 0 )
@@ -136,8 +136,9 @@ int parse_util_get_line_from_offset( wchar_t *buff, int pos )
 }
 
 
-int parse_util_get_offset_from_line( wchar_t *buff, int line )
+int parse_util_get_offset_from_line( const wcstring &str, int line )
 {
+    const wchar_t *buff = str.c_str();
 	int i;
 	int count = 0;
 	
@@ -168,8 +169,9 @@ int parse_util_get_offset_from_line( wchar_t *buff, int line )
 	}
 }
 
-int parse_util_get_offset( wchar_t *buff, int line, int line_offset )
+int parse_util_get_offset( const wcstring &str, int line, int line_offset )
 {
+    const wchar_t *buff = str.c_str();
 	int off = parse_util_get_offset_from_line( buff, line );
 	int off2 = parse_util_get_offset_from_line( buff, line+1 );
 	int line_offset2 = line_offset;
@@ -292,8 +294,8 @@ int parse_util_locate_cmdsubst( const wchar_t *in,
 
 void parse_util_cmdsubst_extent( const wchar_t *buff,
 								 int cursor_pos,
-								 wchar_t **a, 
-								 wchar_t **b )
+								 const wchar_t **a, 
+								 const wchar_t **b )
 {
 	wchar_t *begin, *end;
 	wchar_t *pos;
@@ -363,11 +365,11 @@ void parse_util_cmdsubst_extent( const wchar_t *buff,
 */
 static void job_or_process_extent( const wchar_t *buff,
 								   int cursor_pos,
-								   wchar_t **a, 
-								   wchar_t **b, 
+								   const wchar_t **a, 
+								   const wchar_t **b, 
 								   int process )
 {
-	wchar_t *begin, *end;
+	const wchar_t *begin, *end;
 	int pos;
 	wchar_t *buffcpy;
 	int finished=0;
@@ -460,16 +462,16 @@ static void job_or_process_extent( const wchar_t *buff,
 
 void parse_util_process_extent( const wchar_t *buff,
 								int pos,
-								wchar_t **a, 
-								wchar_t **b )
+								const wchar_t **a, 
+								const wchar_t **b )
 {
 	job_or_process_extent( buff, pos, a, b, 1 );	
 }
 
 void parse_util_job_extent( const wchar_t *buff,
 							int pos,
-							wchar_t **a, 
-							wchar_t **b )
+							const wchar_t **a, 
+							const wchar_t **b )
 {
 	job_or_process_extent( buff,pos,a, b, 0 );	
 }
@@ -477,18 +479,18 @@ void parse_util_job_extent( const wchar_t *buff,
 
 void parse_util_token_extent( const wchar_t *buff,
 							  int cursor_pos,
-							  wchar_t **tok_begin,
-							  wchar_t **tok_end,
-							  wchar_t **prev_begin, 
-							  wchar_t **prev_end )
+							  const wchar_t **tok_begin,
+							  const wchar_t **tok_end,
+							  const wchar_t **prev_begin, 
+							  const wchar_t **prev_end )
 {
-	wchar_t *begin, *end;
+	const wchar_t *begin, *end;
 	int pos;
 	wchar_t *buffcpy;
 
 	tokenizer tok;
 
-	wchar_t *a, *b, *pa, *pb;
+	const wchar_t *a, *b, *pa, *pb;
 	
 	CHECK( buff, );
 		
@@ -505,9 +507,9 @@ void parse_util_token_extent( const wchar_t *buff,
 	
 	pos = cursor_pos - (begin - buff);
 	
-	a = (wchar_t *)buff + pos;
+	a = buff + pos;
 	b = a;
-	pa = (wchar_t *)buff + pos;
+	pa = buff + pos;
 	pb = pa;
 	
 	assert( begin >= buff );
diff --git a/parse_util.h b/parse_util.h
index 001313200..241790cc5 100644
--- a/parse_util.h
+++ b/parse_util.h
@@ -41,8 +41,8 @@ int parse_util_locate_cmdsubst( const wchar_t *in,
 */
 void parse_util_cmdsubst_extent( const wchar_t *buff,
 								 int cursor_pos,
-								 wchar_t **a, 
-								 wchar_t **b );
+								 const wchar_t **a, 
+								 const wchar_t **b );
 
 /**
    Find the beginning and end of the process definition under the cursor
@@ -54,8 +54,8 @@ void parse_util_cmdsubst_extent( const wchar_t *buff,
 */
 void parse_util_process_extent( const wchar_t *buff,
 								int cursor_pos,
-								wchar_t **a, 
-								wchar_t **b );
+								const wchar_t **a, 
+								const wchar_t **b );
 
 
 /**
@@ -68,12 +68,12 @@ void parse_util_process_extent( const wchar_t *buff,
 */
 void parse_util_job_extent( const wchar_t *buff,
 							int cursor_pos,
-							wchar_t **a, 
-							wchar_t **b );
+							const wchar_t **a, 
+							const wchar_t **b );
 
 /**
    Find the beginning and end of the token under the cursor and the
-   toekn before the current token. Any combination of tok_begin,
+   token before the current token. Any combination of tok_begin,
    tok_end, prev_begin and prev_end may be null.
 
    \param buff the string to search for subshells
@@ -85,10 +85,10 @@ void parse_util_job_extent( const wchar_t *buff,
 */
 void parse_util_token_extent( const wchar_t *buff,
 							  int cursor_pos,
-							  wchar_t **tok_begin,
-							  wchar_t **tok_end,
-							  wchar_t **prev_begin, 
-							  wchar_t **prev_end );
+							  const wchar_t **tok_begin,
+							  const wchar_t **tok_end,
+							  const wchar_t **prev_begin, 
+							  const wchar_t **prev_end );
 
 
 /**
@@ -99,18 +99,18 @@ int parse_util_lineno( const wchar_t *str, int len );
 /**
    Calculate the line number of the specified cursor position
  */
-int parse_util_get_line_from_offset( wchar_t *buff, int pos );
+int parse_util_get_line_from_offset( const wcstring &str, int pos );
 
 /**
    Get the offset of the first character on the specified line
  */
-int parse_util_get_offset_from_line( wchar_t *buff, int line );
+int parse_util_get_offset_from_line( const wcstring &str, int line );
 
 
 /**
    Return the total offset of the buffer for the cursor position nearest to the specified poition
  */
-int parse_util_get_offset( wchar_t *buff, int line, int line_offset );
+int parse_util_get_offset( const wcstring &str, int line, int line_offset );
 
 /**
    Set the argv environment variable to the specified null-terminated
diff --git a/reader.cpp b/reader.cpp
index 5958529e5..973f6cd7c 100644
--- a/reader.cpp
+++ b/reader.cpp
@@ -1028,7 +1028,7 @@ static void completion_insert( const wchar_t *val, int flags )
 	{
 		
 		int tok_start, tok_len, move_cursor;
-		wchar_t *begin, *end;
+		const wchar_t *begin, *end;
 		string_buffer_t sb;
 		wchar_t *escaped;
 		
@@ -1225,7 +1225,7 @@ static void run_pager( wchar_t *prefix, int is_quoted, const std::vector<complet
 		  {
 		    if( base_len == -1 )
 		      {
-			wchar_t *begin;
+			const wchar_t *begin;
 				
 			parse_util_token_extent( data->buff, data->buff_pos, &begin, 0, 0, 0 );
 			base_len = data->buff_pos - (begin-data->buff);
@@ -1402,7 +1402,7 @@ static int handle_completions( std::vector<completion_t> &comp )
 	int done = 0;
 	int count = 0;
 	int flags=0;
-	wchar_t *begin, *end;
+	const wchar_t *begin, *end;
 	wchar_t *tok;
 	
 	parse_util_token_extent( data->buff, data->buff_pos, &begin, 0, 0, 0 );
@@ -1757,7 +1757,7 @@ void reader_sanity_check()
 void reader_replace_current_token( const wchar_t *new_token )
 {
 
-	wchar_t *begin, *end;
+	const wchar_t *begin, *end;
 	string_buffer_t sb;
 	int new_pos;
 
@@ -1804,7 +1804,7 @@ static void handle_history( const wcstring &new_str )
 */
 static void reset_token_history()
 {
-	wchar_t *begin, *end;
+	const wchar_t *begin, *end;
 
 	parse_util_token_extent( data->buff, data->buff_pos, &begin, &end, 0, 0 );
 	
@@ -2818,8 +2818,8 @@ wchar_t *reader_readline()
 
  				if( comp_empty || last_char != R_COMPLETE)
 				{
-					wchar_t *begin, *end;
-					wchar_t *token_begin, *token_end;
+					const wchar_t *begin, *end;
+					const wchar_t *token_begin, *token_end;
 					wchar_t *buffcpy;
 					int len;
 					int cursor_steps;