sed: fix zero chars match/replace

function                                             old     new   delta
process_files                                       2099    2181     +82

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

diff --git a/editors/sed.c b/editors/sed.c
index a2df931..87fc755 100644 (file)
--- a/editors/sed.c
+++ b/editors/sed.c
@@ -673,7 +673,7 @@ static void do_subst_w_backrefs(char *line, char *replace)
 
        /* go through the replacement string */
        for (i = 0; replace[i]; i++) {
-               /* if we find a backreference (\1, \2, etc.) print the backref'ed * text */
+               /* if we find a backreference (\1, \2, etc.) print the backref'ed text */
                if (replace[i] == '\\') {
                        unsigned backref = replace[++i] - '0';
                        if (backref <= 9) {
@@ -707,8 +707,10 @@ static void do_subst_w_backrefs(char *line, char *replace)
 static int do_subst_command(sed_cmd_t *sed_cmd, char **line_p)
 {
        char *line = *line_p;
-       int altered = 0;
        unsigned match_count = 0;
+       bool altered = 0;
+       bool prev_match_empty = 1;
+       bool tried_at_eol = 0;
        regex_t *current_regex;
 
        current_regex = sed_cmd->sub_match;
@@ -737,46 +739,64 @@ static int do_subst_command(sed_cmd_t *sed_cmd, char **line_p)
        do {
                int i;
 
-               /* Work around bug in glibc regexec, demonstrated by:
-                * echo " a.b" | busybox sed 's [^ .]* x g'
-                * The match_count check is so not to break
-                * echo "hi" | busybox sed 's/^/!/g'
-                */
-               if (!G.regmatch[0].rm_so && !G.regmatch[0].rm_eo && match_count) {
-                       pipe_putc(*line++);
-                       goto next;
-               }
-
                match_count++;
 
                /* If we aren't interested in this match, output old line to
-                  end of match and continue */
+                * end of match and continue */
                if (sed_cmd->which_match
                 && (sed_cmd->which_match != match_count)
                ) {
                        for (i = 0; i < G.regmatch[0].rm_eo; i++)
                                pipe_putc(*line++);
+                       /* Null match? Print one more char */
+                       if (G.regmatch[0].rm_so == i && *line)
+                               pipe_putc(*line++);
                        goto next;
                }
 
-               /* print everything before the match */
+               /* Print everything before the match */
                for (i = 0; i < G.regmatch[0].rm_so; i++)
                        pipe_putc(line[i]);
 
-               /* then print the substitution string */
-               do_subst_w_backrefs(line, sed_cmd->string);
+               /* Then print the substitution string,
+                * unless we just matched empty string after non-empty one.
+                * Example: string "cccd", pattern "c*", repl "R":
+                * result is "RdR", not "RRdR": first match "ccc",
+                * second is "" before "d", third is "" after "d".
+                * Second match is NOT replaced!
+                */
+               if (prev_match_empty || i != 0) {
+                       dbg("inserting replacement at %d in '%s'", i, line);
+                       do_subst_w_backrefs(line, sed_cmd->string);
+               } else {
+                       dbg("NOT inserting replacement at %d in '%s'", i, line);
+               }
+
+               /* If matched string is empty (f.e. "c*" pattern),
+                * copy verbatim one char after it before attempting more matches
+                */
+               prev_match_empty = (G.regmatch[0].rm_eo == i);
+               if (prev_match_empty && line[i]) {
+                       pipe_putc(line[i]);
+                       G.regmatch[0].rm_eo++;
+               }
 
-               /* advance past the match */
+               /* Advance past the match */
+               dbg("line += %d", G.regmatch[0].rm_eo);
                line += G.regmatch[0].rm_eo;
-               /* flag that something has changed */
-               altered++;
+               /* Flag that something has changed */
+               altered = 1;
 
                /* if we're not doing this globally, get out now */
                if (sed_cmd->which_match != 0)
                        break;
  next:
-               if (*line == '\0')
-                       break;
+               /* Exit if we are at EOL and already tried matching at it */
+               if (*line == '\0') {
+                       if (tried_at_eol)
+                               break;
+                       tried_at_eol = 1;
+               }
 
 //maybe (G.regmatch[0].rm_eo ? REG_NOTBOL : 0) instead of unconditional REG_NOTBOL?
        } while (regexec(current_regex, line, 10, G.regmatch, REG_NOTBOL) != REG_NOMATCH);
@@ -1127,7 +1147,7 @@ static void process_files(void)
                case 's':
                        if (!do_subst_command(sed_cmd, &pattern_space))
                                break;
-                       dbg("do_subst_command succeeeded:'%s'", pattern_space);
+                       dbg("do_subst_command succeeded:'%s'", pattern_space);
                        substituted |= 1;
 
                        /* handle p option */

diff --git a/testsuite/sed.tests b/testsuite/sed.tests
index 9fa8e19..375beb5 100755 (executable)
--- a/testsuite/sed.tests
+++ b/testsuite/sed.tests
@@ -52,10 +52,8 @@ testing "sed with empty match" "sed 's/z*//g'" "string\n" "" "string\n"
 testing "sed s//p" "sed -e s/foo/bar/p -e s/bar/baz/p" "bar\nbaz\nbaz\n" \
        "" "foo\n"
 testing "sed -n s//p" "sed -ne s/abc/def/p" "def\n" "" "abc\n"
-test x"$SKIP_KNOWN_BUGS" = x"" && {
 testing "sed s//g (exhaustive)" "sed -e 's/[[:space:]]*/,/g'" ",1,2,3,4,5,\n" \
        "" "12345\n"
-}
 testing "sed s arbitrary delimiter" "sed -e 's woo boing '" "boing\n" "" "woo\n"
 testing "sed s chains" "sed -e s/foo/bar/ -e s/bar/baz/" "baz\n" "" "foo\n"
 testing "sed s chains2" "sed -e s/foo/bar/ -e s/baz/nee/" "bar\n" "" "foo\n"
@@ -296,6 +294,14 @@ testing "sed -i finishes ranges correctly" \
        "sed '1,2d' -i input; echo \$?; cat input" \
        "0\n3\n4\n" "1\n2\n3\n4\n" ""
 
+testing "sed zero chars match/replace advances correctly 1" \
+       "sed 's/l*/@/g'" \
+       "@h@e@o@\n" "" "helllo\n"
+
+testing "sed zero chars match/replace advances correctly 2" \
+       "sed 's [^ .]* x g'" \
+       "x x.x\n" "" " a.b\n"
+
 # testing "description" "commands" "result" "infile" "stdin"
 
 exit $FAILCOUNT