sed: fix breakage added by zero length match code

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 5 insertions, 1 deletions

diff --git a/editors/sed.c b/editors/sed.c
index 85c84665b..0fe82f337 100644
--- a/editors/sed.c
+++ b/editors/sed.c
@@ -767,7 +767,7 @@ static int do_subst_command(sed_cmd_t *sed_cmd, char **line_p)
                  * second is "" before "d", third is "" after "d".
                  * Second match is NOT replaced!
                  */
-                if (prev_match_empty || start != 0) {
+                if (prev_match_empty || start != 0 || start != end) {
                         dbg("inserting replacement at %d in '%s'", start, line);
                         do_subst_w_backrefs(line, sed_cmd->string);
                 } else {
diff --git a/testsuite/sed.tests b/testsuite/sed.tests
index 375beb518..12b36ae18 100755
--- a/testsuite/sed.tests
+++ b/testsuite/sed.tests
@@ -302,6 +302,10 @@ testing "sed zero chars match/replace advances correctly 2" \
         "sed 's [^ .]* x g'" \
         "x x.x\n" "" " a.b\n"
 
+testing "sed zero chars match/replace logic must not falsely trigger here" \
+        "sed 's/a/A/g'" \
+        "_AAA1AA\n" "" "_aaa1aa\n"
+
 # testing "description" "commands" "result" "infile" "stdin"
 
 exit $FAILCOUNT