1 files changed, 73 insertions, 24 deletions

diff --git a/coreutils/sort.c b/coreutils/sort.c
index ceea24491..b39297a26 100644
--- a/coreutils/sort.c
+++ b/coreutils/sort.c
@@ -62,9 +62,9 @@
 //usage:     "\n        -u      Suppress duplicate lines"
 //usage:        IF_FEATURE_SORT_BIG(
 //usage:     "\n        -z      Lines are terminated by NUL, not newline"
-////usage:     "\n      -m      Ignored for GNU compatibility"
-////usage:     "\n      -S BUFSZ Ignored for GNU compatibility"
-////usage:     "\n      -T TMPDIR Ignored for GNU compatibility"
+///////:     "\n        -m      Ignored for GNU compatibility"
+///////:     "\n        -S BUFSZ Ignored for GNU compatibility"
+///////:     "\n        -T TMPDIR Ignored for GNU compatibility"
 //usage:        )
 //usage:
 //usage:#define sort_example_usage
@@ -85,16 +85,7 @@
 
 #include "libbb.h"
 
-/* This is a NOEXEC applet. Be very careful! */
-
-
-/*
-        sort [-m][-o output][-bdfinru][-t char][-k keydef]... [file...]
-        sort -c [-bdfinru][-t char][-k keydef][file]
-*/
-
 /* These are sort types */
-#define OPT_STR "ngMucszbrdfimS:T:o:k:*t:"
 enum {
         FLAG_n  = 1,            /* Numeric sort */
         FLAG_g  = 2,            /* Sort using strtod() */
@@ -117,8 +108,18 @@ enum {
         FLAG_k  = 0x10000,
         FLAG_t  = 0x20000,
         FLAG_bb = 0x80000000,   /* Ignore trailing blanks  */
+        FLAG_no_tie_break = 0x40000000,
 };
 
+static const char sort_opt_str[] ALIGN1 = "^"
+                        "ngMucszbrdfimS:T:o:k:*t:"
+                        "\0" "o--o:t--t"/*-t, -o: at most one of each*/;
+/*
+ * OPT_STR must not be string literal, needs to have stable address:
+ * code uses "strchr(OPT_STR,c) - OPT_STR" idiom.
+ */
+#define OPT_STR (sort_opt_str + 1)
+
 #if ENABLE_FEATURE_SORT_BIG
 static char key_separator;
 
@@ -128,6 +129,10 @@ static struct sort_key {
         unsigned flags;
 } *key_list;
 
+
+/* This is a NOEXEC applet. Be very careful! */
+
+
 static char *get_key(char *str, struct sort_key *key, int flags)
 {
         int start = start; /* for compiler */
@@ -340,10 +345,35 @@ static int compare_keys(const void *xarg, const void *yarg)
 #endif
         } /* for */
 
-        /* Perform fallback sort if necessary */
-        if (!retval && !(option_mask32 & FLAG_s)) {
-                flags = option_mask32;
-                retval = strcmp(*(char **)xarg, *(char **)yarg);
+        if (retval == 0) {
+                /* So far lines are "the same" */
+
+                if (option_mask32 & FLAG_s) {
+                        /* "Stable sort": later line is "greater than",
+                         * IOW: do not allow qsort() to swap equal lines.
+                         */
+                        uint32_t *p32;
+                        uint32_t x32, y32;
+                        char *line;
+                        unsigned len;
+
+                        line = *(char**)xarg;
+                        len = (strlen(line) + 4) & (~3u);
+                        p32 = (void*)(line + len);
+                        x32 = *p32;
+                        line = *(char**)yarg;
+                        len = (strlen(line) + 4) & (~3u);
+                        p32 = (void*)(line + len);
+                        y32 = *p32;
+
+                        /* If x > y, 1, else -1 */
+                        retval = (x32 > y32) * 2 - 1;
+                } else
+                if (!(option_mask32 & FLAG_no_tie_break)) {
+                        /* fallback sort */
+                        flags = option_mask32;
+                        retval = strcmp(*(char **)xarg, *(char **)yarg);
+                }
         }
 
         if (flags & FLAG_r)
@@ -368,7 +398,7 @@ static unsigned str2u(char **str)
 int sort_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int sort_main(int argc UNUSED_PARAM, char **argv)
 {
-        char *line, **lines;
+        char **lines;
         char *str_ignored, *str_o, *str_t;
         llist_t *lst_k = NULL;
         int i;
@@ -378,9 +408,8 @@ int sort_main(int argc UNUSED_PARAM, char **argv)
         xfunc_error_retval = 2;
 
         /* Parse command line options */
-        opts = getopt32(argv, "^"
-                        OPT_STR
-                        "\0" "o--o:t--t"/*-t, -o: at most one of each*/,
+        opts = getopt32(argv,
+                        sort_opt_str,
                         &str_ignored, &str_ignored, &str_o, &lst_k, &str_t
         );
         /* global b strips leading and trailing spaces */
@@ -457,7 +486,7 @@ int sort_main(int argc UNUSED_PARAM, char **argv)
                  * do not continue to next file: */
                 FILE *fp = xfopen_stdin(*argv);
                 for (;;) {
-                        line = GET_LINE(fp);
+                        char *line = GET_LINE(fp);
                         if (!line)
                                 break;
                         lines = xrealloc_vector(lines, 6, linecount);
@@ -482,15 +511,35 @@ int sort_main(int argc UNUSED_PARAM, char **argv)
                 return EXIT_SUCCESS;
         }
 #endif
+
+        /* For stable sort, store original line position beyond terminating NUL */
+        if (option_mask32 & FLAG_s) {
+                for (i = 0; i < linecount; i++) {
+                        uint32_t *p32;
+                        char *line;
+                        unsigned len;
+
+                        line = lines[i];
+                        len = (strlen(line) + 4) & (~3u);
+                        lines[i] = line = xrealloc(line, len + 4);
+                        p32 = (void*)(line + len);
+                        *p32 = i;
+                }
+                /*option_mask32 |= FLAG_no_tie_break;*/
+                /* ^^^redundant: if FLAG_s, compare_keys() does no tie break */
+        }
+
         /* Perform the actual sort */
         qsort(lines, linecount, sizeof(lines[0]), compare_keys);
 
         /* Handle -u */
         if (option_mask32 & FLAG_u) {
                 int j = 0;
-                /* coreutils 6.3 drop lines for which only key is the same */
-                /* -- disabling last-resort compare... */
-                option_mask32 |= FLAG_s;
+                /* coreutils 6.3 drop lines for which only key is the same
+                 * -- disabling last-resort compare, or else compare_keys()
+                 * will be the same only for completely identical lines.
+                 */
+                option_mask32 |= FLAG_no_tie_break;
                 for (i = 1; i < linecount; i++) {
                         if (compare_keys(&lines[j], &lines[i]) == 0)
                                 free(lines[i]);