libbb: introduce and use xasprintf_inplace()

function                                             old     new   delta
xasprintf_and_free                                     -      49     +49
watch_main                                           269     282     +13
singlemount                                         1313    1315      +2
append_mount_options                                 157     149      -8
ip_port_str                                          122     112     -10
lsblk_main                                           869     858     -11
add_cmd                                             1178    1167     -11
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/4 up/down: 64/-40)             Total: 24 bytes

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

1 files changed, 15 insertions, 10 deletions

diff --git a/util-linux/mount.c b/util-linux/mount.c
index d0f0ae1ad..d0d109c09 100644
--- a/util-linux/mount.c
+++ b/util-linux/mount.c
@@ -556,27 +556,33 @@ static int verbose_mount(const char *source, const char *target,
 #endif
 
 // Append mount options to string
+// ("merge two comma-separated lists" is a good candidate for libbb!)
 static void append_mount_options(char **oldopts, const char *newopts)
 {
         if (*oldopts && **oldopts) {
+//TODO: do this unconditionally?
+//this way, newopts of "opt1,opt2,opt1"
+//will be de-duped into "opt1,opt2" in _both_ cases
+//(whether or now old opts are empty)
+//the only modification needed is to not prepend extra comma
+//when old opts is "".
                 // Do not insert options which are already there
-                while (newopts[0]) {
+                while (*newopts) {
                         char *p;
                         int len;
 
+                        //if (*newopts == ',') { newopts++; continue; }
                         len = strchrnul(newopts, ',') - newopts;
                         p = *oldopts;
                         while (1) {
-                                if (!strncmp(p, newopts, len)
+                                if (strncmp(p, newopts, len) == 0
                                  && (p[len] == ',' || p[len] == '\0'))
                                         goto skip;
-                                p = strchr(p,',');
+                                p = strchr(p, ',');
                                 if (!p) break;
                                 p++;
                         }
-                        p = xasprintf("%s,%.*s", *oldopts, len, newopts);
-                        free(*oldopts);
-                        *oldopts = p;
+                        xasprintf_inplace(*oldopts, "%s,%.*s", *oldopts, len, newopts);
  skip:
                         newopts += len;
                         while (*newopts == ',') newopts++;
@@ -2065,12 +2071,11 @@ static int singlemount(struct mntent *mp, int ignore_busy)
                 if (!is_prefixed_with(filteropts, ",ip="+1)
                  && !strstr(filteropts, ",ip=")
                 ) {
-                        char *dotted, *ip;
+                        char *ip;
                         // Insert "ip=..." option into options
-                        dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
+                        ip = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
                         if (ENABLE_FEATURE_CLEAN_UP) free(lsa);
-                        ip = xasprintf("ip=%s", dotted);
-                        if (ENABLE_FEATURE_CLEAN_UP) free(dotted);
+                        xasprintf_inplace(ip, "ip=%s", ip);
 // Note: IPv6 scoped addresses ("host%iface", see RFC 4007) should be
 // handled by libc in getnameinfo() (inside xmalloc_sockaddr2dotted_noport()).
 // Currently, glibc does not support that (has no NI_NUMERICSCOPE),