fixed fencepost errors with yy_buf_size and detecting NUL's

diff --git a/flex.skl b/flex.skl
index fe0a56786fed2e91497bb0cc621aad01b790e280..01f70ab261abbca9885a3885f50afcdd534b699f 100644 (file)
--- a/flex.skl
+++ b/flex.skl
@@ -153,8 +153,12 @@ struct yy_buffer_state
 
     YY_CHAR *yy_ch_buf;                /* input buffer */
     YY_CHAR *yy_buf_pos;       /* current position in input buffer */
-    int yy_buf_size;           /* size of input buffer in bytes */
-    int yy_n_chars;            /* number of characters read into yy_ch_buf */
+
+    /* size of input buffer in bytes, not including room for EOB characters*/
+    int yy_buf_size;   
+
+    /* number of characters read into yy_ch_buf, not including EOB characters */
+    int yy_n_chars;
 
     int yy_eof_status;         /* whether we've seen an EOF on this buffer */
 #define EOF_NOT_SEEN 0
@@ -290,8 +294,13 @@ do_action: /* this label is used only to access EOF actions */
                /* undo the effects of YY_DO_BEFORE_ACTION */
                *yy_cp = yy_hold_char;
 
-               if ( yy_c_buf_p <
-                    &yy_current_buffer->yy_ch_buf[yy_n_chars + 1] )
+               /* note that here we test for yy_c_buf_p "<=" to the position
+                * of the first EOB in the buffer, since yy_c_buf_p will
+                * already have been incremented past the NUL character
+                * (since all states make transitions on EOB to the end-
+                * of-buffer state).  Contrast this with the test in yyinput().
+                */
+               if ( yy_c_buf_p <= &yy_current_buffer->yy_ch_buf[yy_n_chars] )
                    /* this was really a NUL */
                    {
                    yy_state_type yy_next_state;
@@ -575,7 +584,11 @@ static int input()
 
     if ( *yy_c_buf_p == YY_END_OF_BUFFER_CHAR )
        {
-       if ( yy_c_buf_p < &yy_current_buffer->yy_ch_buf[yy_n_chars + 1] )
+       /* yy_c_buf_p now points to the character we want to return.
+        * If this occurs *before* the EOB characters, then it's a
+        * valid NUL; if not, then we've hit the end of the buffer.
+        */
+       if ( yy_c_buf_p < &yy_current_buffer->yy_ch_buf[yy_n_chars] )
            /* this was really a NUL */
            *yy_c_buf_p = '\0';
 
@@ -692,11 +705,12 @@ int size;
     if ( ! b )
        YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );
 
+    b->yy_buf_size = size;
+
     /* yy_ch_buf has to be 2 characters longer than the size given because
      * we need to put in 2 end-of-buffer characters.
      */
-    b->yy_buf_size = size + 2;
-    b->yy_ch_buf = (YY_CHAR *) malloc( (unsigned) b->yy_buf_size );
+    b->yy_ch_buf = (YY_CHAR *) malloc( (unsigned) (b->yy_buf_size + 2) );
 
     if ( ! b->yy_ch_buf )
        YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );