Handle comments

Ignore C/C++ style comments, and also handle a few error
cases a slight bit more elegently.

Signed-off-by: Stephen Williams <steve@icarus.com>

vpi/sdf_lexor.lex

@@ -41,8 +41,19 @@ static int yywrap(void)
 # define yylval sdflval
 %}
 
+%x CCOMMENT
+
 %%
 
+  /* Skip C++-style comments. */
+"//".* { sdflloc.first_line += 1; }
+
+  /* Skip C-style comments. */
+"/*"           { BEGIN(CCOMMENT); }
+<CCOMMENT>.    { yymore(); }
+<CCOMMENT>\n   { sdflloc.first_line += 1; yymore(); }
+<CCOMMENT>"*/" { BEGIN(0); }
+
 [ \m\t] { /* Skip white space. */; }
 
   /* Count lines so that the parser can assign line numbers. */

vpi/sdf_parse.y

@@ -62,6 +62,10 @@ static char use_hchar = '.';
 
 source_file
   : '(' K_DELAYFILE sdf_header_list cell_list ')'
+  | '(' K_DELAYFILE error ')'
+      { vpi_printf("%s:%d:SDF ERROR: Invalid DELAYFILE format\n",
+		   sdf_parse_path, @2.first_line);
+      }
   ;
 
 sdf_header_list
@@ -304,5 +308,5 @@ signed_real_number
 
 void yyerror(const char*msg)
 {
-      fprintf(stderr, "SDF ERROR: %s\n", msg);
+      vpi_printf("%s:SDF ERROR: Too many errors: %s\n", sdf_parse_path, msg);
 }