From 481dc9b0e831a65ec44daae4c076927110218ad6 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 23 Feb 2017 19:54:34 -0700
Subject: [PATCH] fix port line, col, and pos to stay at #f when set to #f

---
 pkgs/racket-test-core/tests/racket/port.rktl | 23 ++++++++++++++++
 racket/src/racket/src/port.c                 | 29 ++++++++++----------
 racket/src/racket/src/print.c                |  5 ++--
 3 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/pkgs/racket-test-core/tests/racket/port.rktl b/pkgs/racket-test-core/tests/racket/port.rktl
index 6b06706ae5..c9f71f63ee 100644
--- a/pkgs/racket-test-core/tests/racket/port.rktl
+++ b/pkgs/racket-test-core/tests/racket/port.rktl
@@ -945,6 +945,29 @@
   (test 5 file-position p)
   (test  "abcde" read-string 5 p))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Check that lines, columns, and positions stay at #f when set to #f
+
+(let ()
+  (define (check-srcloc line col pos)
+    (define stx-port (open-input-string "A\n B"))
+    (port-count-lines! stx-port)
+    (set-port-next-location! stx-port line col pos)
+    (define a (read-syntax #f stx-port))
+    (define b (read-syntax #f stx-port))
+    (test line syntax-line a)
+    (test col syntax-column a)
+    (test pos syntax-position a)
+    (test (and line (add1 line)) syntax-line b)
+    (test (and col 1) syntax-column b)
+    (test (and pos (+ 3 pos)) syntax-position b))
+  (check-srcloc #f #f #f)
+  (check-srcloc #f #f 29)
+  (check-srcloc 1 #f 29)
+  (check-srcloc #f 3 29)
+  (check-srcloc #f 3 #f)
+  (check-srcloc 1 3 29))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)
diff --git a/racket/src/racket/src/port.c b/racket/src/racket/src/port.c
index 5613de63dc..4fe745c1cd 100644
--- a/racket/src/racket/src/port.c
+++ b/racket/src/racket/src/port.c
@@ -2048,8 +2048,10 @@ static void post_progress(Scheme_Input_Port *ip)
 
 XFORM_NONGCING static void inc_pos(Scheme_Port *ip, int a)
 {
-  ip->column += a;
-  ip->readpos += a;
+  if (ip->column >= 0)
+    ip->column += a;
+  if (ip->readpos >= 0)
+    ip->readpos += a;
   ip->charsSinceNewline += a;
   ip->utf8state = 0;
 }
@@ -2081,13 +2083,10 @@ XFORM_NONGCING static void do_count_lines(Scheme_Port *ip, const char *buffer, i
   intptr_t i;
   int c, degot = 0;
 
-  mzAssert(ip->lineNumber >= 0);
-  mzAssert(ip->column >= 0);
-  mzAssert(ip->position >= 0);
-
   ip->oldColumn = ip->column; /* works for a single-char read, like `read' */
 
-  ip->readpos += got; /* add for CR LF below */
+  if (ip->readpos >= 0)
+    ip->readpos += got; /* add for CR LF below */
 
   /* Find start of last line: */
   for (i = got, c = 0; i--; c++) {
@@ -2125,10 +2124,12 @@ XFORM_NONGCING static void do_count_lines(Scheme_Port *ip, const char *buffer, i
     }
 	 	  
     mzAssert(n > 0);
-    ip->lineNumber += n;
+    if (ip->lineNumber >= 0)
+      ip->lineNumber += n;
     ip->was_cr = (buffer[offset + got - 1] == '\r');
     /* Now reset column to 0: */
-    ip->column = 0;
+    if (ip->column >= 0)
+      ip->column = 0;
   } else {
     ip->charsSinceNewline += c;
   }
@@ -2157,15 +2158,13 @@ XFORM_NONGCING static void do_count_lines(Scheme_Port *ip, const char *buffer, i
       col += n;
       degot += ((i - prev_i) - n);
     }
-    ip->column = col;
+    if (ip->column >= 0)
+      ip->column = col;
     ip->utf8state = state;
   }
 
-  ip->readpos -= degot;
-
-  mzAssert(ip->lineNumber >= 0);
-  mzAssert(ip->column >= 0);
-  mzAssert(ip->position >= 0);
+  if (ip->readpos >= 0)
+    ip->readpos -= degot;
 }
 
 void scheme_port_count_lines(Scheme_Port *ip, const char *buffer, intptr_t offset, intptr_t got)
diff --git a/racket/src/racket/src/print.c b/racket/src/racket/src/print.c
index 29c0189efc..a6b915f03f 100644
--- a/racket/src/racket/src/print.c
+++ b/racket/src/racket/src/print.c
@@ -3002,11 +3002,12 @@ print(Scheme_Object *obj, int notdisplay, int compact, Scheme_Hash_Table *ht,
 	    print_utf8_string(pp, SCHEME_BYTE_STR_VAL(stx->srcloc->src), 0, SCHEME_BYTE_STRLEN_VAL(stx->srcloc->src));
 	    print_utf8_string(pp, ":", 0, 1);
 	  }
-	  if (stx->srcloc->line >= 0)
+	  if ((stx->srcloc->line >= 0)
+              && (stx->srcloc->col >= 0))
 	    sprintf(quick_buffer, 
 		    "%" PRIdPTR ":%" PRIdPTR "", 
 		    stx->srcloc->line, stx->srcloc->col-1);
-	  else
+	  else if (stx->srcloc->pos >= 0)
 	    sprintf(quick_buffer, ":%" PRIdPTR "", 
 		    stx->srcloc->pos);
 	  print_utf8_string(pp, quick_buffer, 0, -1);