grep: fix buglets with context printing

print_line                                           152     170     +18
did_print_line                                         -       1      +1
grep_file                                            788     771     -17
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 19/-17)              Total: 2 bytes
   text    data     bss     dec     hex filename
 673368    2740   13968  690076   a879c busybox_old
 673368    2740   13968  690076   a879c busybox_unstripped

1 files changed, 42 insertions, 28 deletions

diff --git a/findutils/grep.c b/findutils/grep.c
index 75425b4df..7bade87cb 100644
--- a/findutils/grep.c
+++ b/findutils/grep.c
@@ -91,6 +91,7 @@ static byte_t print_filename;
 static byte_t open_errors;
 
 #if ENABLE_FEATURE_GREP_CONTEXT
+static byte_t did_print_line;
 static int lines_before;
 static int lines_after;
 static char **before_buf;
@@ -112,11 +113,17 @@ typedef struct grep_list_data_t {
 static void print_line(const char *line, int linenum, char decoration)
 {
 #if ENABLE_FEATURE_GREP_CONTEXT
+        /* Happens when we go to next file, immediately hit match
+         * and try to print prev context... from prev file! Don't do it */
+        if (linenum < 1)
+                return;
         /* possibly print the little '--' separator */
-        if ((lines_before || lines_after) && last_line_printed &&
-                        last_line_printed < linenum - 1) {
+        if ((lines_before || lines_after) && did_print_line &&
+                        last_line_printed != linenum - 1) {
                 puts("--");
         }
+        /* guard against printing "--" before first line of first file */
+        did_print_line = 1;
         last_line_printed = linenum;
 #endif
         if (print_filename)
@@ -124,7 +131,7 @@ static void print_line(const char *line, int linenum, char decoration)
         if (PRINT_LINE_NUM)
                 printf("%i%c", linenum, decoration);
         /* Emulate weird GNU grep behavior with -ov */
-        if ((option_mask32 & (OPT_v+OPT_o)) != (OPT_v+OPT_o))
+        if ((option_mask32 & (OPT_v|OPT_o)) != (OPT_v|OPT_o))
                 puts(line);
 }
 
@@ -183,19 +190,27 @@ static int grep_file(FILE *file)
                 } /* while (pattern_ptr) */
 
                 if (ret ^ invert_search) {
-                        if (PRINT_FILES_WITH_MATCHES || BE_QUIET)
-                                free(line);
-
-                        /* if we found a match but were told to be quiet, stop here */
-                        if (BE_QUIET || PRINT_FILES_WITHOUT_MATCHES)
-                                return -1;
-
                         /* keep track of matches */
                         nmatches++;
 
-                        /* if we're just printing filenames, we stop after the first match */
-                        if (PRINT_FILES_WITH_MATCHES)
-                                break;
+                        /* quiet/print (non)matching file names only? */
+                        if (option_mask32 & (OPT_q|OPT_l|OPT_L)) {
+                                free(line); /* we don't need line anymore */
+                                if (BE_QUIET) {
+                                        /* manpage says about -q:
+                                         * "exit immediately with zero status
+                                         * if any match is found,
+                                         * even if errors were detected" */
+                                        exit(0);
+                                }
+                                /* if we're just printing filenames, we stop after the first match */
+                                if (PRINT_FILES_WITH_MATCHES) {
+                                        puts(cur_file);
+                                        /* fall thru to "return 1" */
+                                }
+                                /* OPT_L aka PRINT_FILES_WITHOUT_MATCHES: return early */
+                                return 1; /* one match */
+                        }
 
                         /* print the matched line */
                         if (PRINT_MATCH_COUNTS == 0) {
@@ -239,19 +254,20 @@ static int grep_file(FILE *file)
                 }
 #if ENABLE_FEATURE_GREP_CONTEXT
                 else { /* no match */
-                        /* Add the line to the circular 'before' buffer */
-                        if (lines_before) {
+                        /* if we need to print some context lines after the last match, do so */
+                        if (print_n_lines_after /* && (last_line_printed != linenum) */ ) {
+                                print_line(line, linenum, '-');
+                                print_n_lines_after--;
+                        } else if (lines_before) {
+                                /* Add the line to the circular 'before' buffer */
                                 free(before_buf[curpos]);
-                                before_buf[curpos] = xstrdup(line);
+                                before_buf[curpos] = line;
                                 curpos = (curpos + 1) % lines_before;
+                                /* avoid free(line) - we took line */
+                                continue;
                         }
                 }
 
-                /* if we need to print some context lines after the last match, do so */
-                if (print_n_lines_after && (last_line_printed != linenum)) {
-                        print_line(line, linenum, '-');
-                        print_n_lines_after--;
-                }
 #endif /* ENABLE_FEATURE_GREP_CONTEXT */
                 free(line);
         }
@@ -266,13 +282,11 @@ static int grep_file(FILE *file)
                 printf("%d\n", nmatches);
         }
 
-        /* grep -l: print just the filename, but only if we grepped the line in the file  */
-        if (PRINT_FILES_WITH_MATCHES && nmatches > 0) {
-                puts(cur_file);
-        }
-
-        /* grep -L: print just the filename, but only if we didn't grep the line in the file  */
-        if (PRINT_FILES_WITHOUT_MATCHES && nmatches == 0) {
+        /* grep -L: print just the filename */
+        if (PRINT_FILES_WITHOUT_MATCHES) {
+                /* nmatches is zero, no need to check it:
+                 * we return 1 early if we detected a match
+                 * and PRINT_FILES_WITHOUT_MATCHES is set */
                 puts(cur_file);
         }