From 2009419979a3392b23d21b40731cfece8dc935f9 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 24 Apr 2007 01:50:09 +0000
Subject: [PATCH] fix read-error reporting for characters that live in no port

svn: r6031
---
 collects/tests/mzscheme/read.ss | 5 +++++
 src/mzscheme/src/error.c        | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/collects/tests/mzscheme/read.ss b/collects/tests/mzscheme/read.ss
index 9ea8bc9006..09c02da8ec 100644
--- a/collects/tests/mzscheme/read.ss
+++ b/collects/tests/mzscheme/read.ss
@@ -951,6 +951,11 @@
 (test #\{ syntax-property (read-syntax 'x (open-input-string "{1 2 3}")) 'paren-shape)
 (test #\{ syntax-property (read-syntax 'x (open-input-string "#{1 2}")) 'paren-shape)
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Test read error on a character not in any port
+
+(err/rt-test (read/recursive (open-input-string ";") #\. #f) exn:fail:read?)
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)
diff --git a/src/mzscheme/src/error.c b/src/mzscheme/src/error.c
index 34b01fe818..6df7de67b0 100644
--- a/src/mzscheme/src/error.c
+++ b/src/mzscheme/src/error.c
@@ -1323,6 +1323,11 @@ void scheme_read_err(Scheme_Object *port,
 
   show_loc = SCHEME_TRUEP(scheme_get_param(scheme_current_config(), MZCONFIG_ERROR_PRINT_SRCLOC));
 
+  /* Via read/recursive, it's possible that the reader will try to
+     complain about a character that precedes the start of a port.
+     In that case, pos can be 0. */
+  if (!pos) line = col = pos = -1;
+
   if (stxsrc) {
     Scheme_Object *xsrc;