Line 0 is a special line added to allow operations with
empty buffers, and we have to ensure that it is not going
to match any regular expression. The code was written in
a way that this case was handle implicitily, but this
solution was working only for the first file loaded in
ed, while the second file loaded in ed got a line with
a dirty seek field. This solution check explicitily
against invalid lines passed to makeline(), which
allows to simplify the common case.
---
 ed.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/ed.c b/ed.c
index 686d2aa..c560d1a 100644
--- a/ed.c
+++ b/ed.c
@@ -169,20 +169,20 @@ makeline(char *s, int *off)
        }
        lp = zero + lastidx;
 
-       while ((c = *s) && *s != '\n')
-               ++s;
-       if (c == '\n')
-               ++s;
-       len = s - begin;
+       if (!s) {
+               lp->seek = -1;
+               len = 0;
+       } else {
+               while ((c = *s++) != '\n')
+                       /* nothing */;
+               len = s - begin;
+               if ((lp->seek = lseek(scratch, 0, SEEK_END)) < 0 ||
+                   write(scratch, begin, len) < 0) {
+                       error("input/output error");
+               }
+       }
        if (off)
                *off = len;
-
-       if (len > 0)
-       if ((lp->seek = lseek(scratch, 0, SEEK_END)) < 0 ||
-           write(scratch, begin, len) < 0) {
-               error("input/output error");
-       }
-
        ++lastidx;
        return lp - zero;
 }
@@ -210,8 +210,11 @@ gettxt(int line)
        char *p;
 
        lp = zero + getindex(line);
-       off = lp->seek;
        sizetxt = 0;
+       off = lp->seek;
+
+       if (off == (off_t) -1)
+               return text = addchar('\0', text, &memtxt, &sizetxt);
 
 repeat:
        if (!csize || off < lasto || off - lasto >= csize) {
@@ -341,7 +344,7 @@ setscratch()
                error("scratch filename too long");
        if ((scratch = mkstemp(tmpname)) < 0)
                error("failed to create scratch file");
-       if ((k = makeline("", NULL)))
+       if ((k = makeline(NULL, NULL)))
                error("input/output error in scratch file");
        relink(k, k, k, k);
        clearundo();
-- 
2.1.4


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