grep: fix two bugs with -w

Unfortunately, with !EXTRA_COMPAT, "grep -w ^str" still erroneously matches "strstr".

function                                             old     new   delta
grep_file                                           1499    1510     +11

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

2 files changed, 37 insertions, 3 deletions

diff --git a/findutils/grep.c b/findutils/grep.c
index b8ad1bf8f..a7bc4ca9e 100644
--- a/findutils/grep.c
+++ b/findutils/grep.c
@@ -373,6 +373,9 @@ static int grep_file(FILE *file)
  opt_f_not_found: ;
                                 }
                         } else {
+#if ENABLE_EXTRA_COMPAT
+                                unsigned start_pos;
+#endif
                                 char *match_at;
 
                                 if (!(gl->flg_mem_alocated_compiled & COMPILED)) {
@@ -389,15 +392,18 @@ static int grep_file(FILE *file)
 #if !ENABLE_EXTRA_COMPAT
                                 gl->matched_range.rm_so = 0;
                                 gl->matched_range.rm_eo = 0;
+#else
+                                start_pos = 0;
 #endif
                                 match_at = line;
  opt_w_again:
+//bb_error_msg("'%s' start_pos:%d line_len:%d", match_at, start_pos, line_len);
                                 if (
 #if !ENABLE_EXTRA_COMPAT
                                         regexec(&gl->compiled_regex, match_at, 1, &gl->matched_range, 0) == 0
 #else
                                         re_search(&gl->compiled_regex, match_at, line_len,
-                                                        /*start:*/ 0, /*range:*/ line_len,
+                                                        start_pos, /*range:*/ line_len,
                                                         &gl->matched_range) >= 0
 #endif
                                 ) {
@@ -416,8 +422,24 @@ static int grep_file(FILE *file)
                                                         if (!c || (!isalnum(c) && c != '_')) {
                                                                 found = 1;
                                                         } else {
-                                                                match_at += gl->matched_range.rm_eo;
-                                                                goto opt_w_again;
+                        /*
+                         * Why check gl->matched_range.rm_eo?
+                         * Zero-length match makes -w skip the line:
+                         * "echo foo | grep ^" prints "foo",
+                         * "echo foo | grep -w ^" prints nothing.
+                         * Without such check, we can loop forever.
+                         */
+#if !ENABLE_EXTRA_COMPAT
+                                                                if (gl->matched_range.rm_eo != 0) {
+                                                                        match_at += gl->matched_range.rm_eo;
+                                                                        goto opt_w_again;
+                                                                }
+#else
+                                                                if (gl->matched_range.rm_eo > start_pos) {
+                                                                        start_pos = gl->matched_range.rm_eo;
+                                                                        goto opt_w_again;
+                                                                }
+#endif
                                                         }
                                                 }
                                         }
diff --git a/testsuite/grep.tests b/testsuite/grep.tests
index 64d99a905..412efffbb 100755
--- a/testsuite/grep.tests
+++ b/testsuite/grep.tests
@@ -147,6 +147,18 @@ testing "grep -w doesn't stop on 1st mismatch" \
         "foop foo\n" \
         ""
 
+testing "grep -w ^str doesn't match str not at the beginning" \
+        "grep -w ^str input" \
+        "" \
+        "strstr\n" \
+        ""
+
+testing "grep -w ^ doesn't hang" \
+        "grep -w ^ input" \
+        "" \
+        "anything\n" \
+        ""
+
 # testing "test name" "commands" "expected result" "file input" "stdin"
 #   file input will be file called "input"
 #   test can create a file "actual" instead of writing to stdout