grep: make "-f -" work (+ testsuite)

diff: small code shrink

function                                             old     new   delta
grep_main                                            722     714      -8
diffreg                                             1825    1793     -32
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-40)             Total: -40 bytes

3 files changed, 13 insertions, 8 deletions

diff --git a/editors/diff.c b/editors/diff.c
index eac4b08c5..4e51f6f76 100644
--- a/editors/diff.c
+++ b/editors/diff.c
@@ -1021,11 +1021,12 @@ static unsigned diffreg(char *file1, char *file2, int flags)
         rval = D_SAME;
 
         if (flags & D_EMPTY1)
-                f1 = xfopen(bb_dev_null, "r");
+                /* can't be stdin, but xfopen_stdin() is smaller code */
+                f1 = xfopen_stdin(bb_dev_null);
         else
                 f1 = xfopen_stdin(file1);
         if (flags & D_EMPTY2)
-                f2 = xfopen(bb_dev_null, "r");
+                f2 = xfopen_stdin(bb_dev_null);
         else
                 f2 = xfopen_stdin(file2);
 
diff --git a/findutils/grep.c b/findutils/grep.c
index 6af1b46e1..fc7893860 100644
--- a/findutils/grep.c
+++ b/findutils/grep.c
@@ -126,7 +126,7 @@ struct globals {
 typedef struct grep_list_data_t {
         char *pattern;
         regex_t preg;
-#define PATTERN_MEM_A 1
+#define ALLOCATED 1
 #define COMPILED 2
         int flg_mem_alocated_compiled;
 } grep_list_data_t;
@@ -363,10 +363,10 @@ static void load_regexes_from_file(llist_t *fopt)
 
                 fopt = cur->link;
                 free(cur);
-                f = xfopen(ffile, "r");
+                f = xfopen_stdin(ffile);
                 while ((line = xmalloc_fgetline(f)) != NULL) {
                         llist_add_to(&pattern_head,
-                                new_grep_list_data(line, PATTERN_MEM_A));
+                                new_grep_list_data(line, ALLOCATED));
                 }
         }
 }
@@ -486,7 +486,7 @@ int grep_main(int argc, char **argv)
                 argc--;
         }
 
-        /* argv[(optind)..(argc-1)] should be names of file to grep through. If
+        /* argv[0..(argc-1)] should be names of file to grep through. If
          * there is more than one file to grep, we will print the filenames. */
         if (argc > 1)
                 print_filename = 1;
@@ -535,9 +535,9 @@ int grep_main(int argc, char **argv)
                         grep_list_data_t *gl = (grep_list_data_t *)pattern_head_ptr->data;
 
                         pattern_head = pattern_head->link;
-                        if ((gl->flg_mem_alocated_compiled & PATTERN_MEM_A))
+                        if (gl->flg_mem_alocated_compiled & ALLOCATED)
                                 free(gl->pattern);
-                        if ((gl->flg_mem_alocated_compiled & COMPILED))
+                        if (gl->flg_mem_alocated_compiled & COMPILED)
                                 regfree(&(gl->preg));
                         free(gl);
                         free(pattern_head_ptr);
diff --git a/testsuite/grep.tests b/testsuite/grep.tests
index 34c0fe4f7..b2de2af54 100755
--- a/testsuite/grep.tests
+++ b/testsuite/grep.tests
@@ -78,6 +78,10 @@ testing "grep handles multiple regexps" "grep -e one -e two input ; echo \$?" \
 testing "grep -F handles multiple expessions" "grep -F -e one -e two input ; echo \$?" \
         "one\ntwo\n0\n" "one\ntwo\n" ""
 
+# -f file/-
+testing "grep can read regexps from stdin" "grep -f - input ; echo \$?" \
+        "two\nthree\n0\n" "tw\ntwo\nthree\n" "tw.\nthr\n"
+
 optional FEATURE_GREP_EGREP_ALIAS
 testing "grep -E supports extended regexps" "grep -E fo+" "foo\n" "" \
         "b\ar\nfoo\nbaz"