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>

9 files changed, 48 insertions, 34 deletions

diff --git a/editors/sed.c b/editors/sed.c
index 6179c5e80..029e9b8e7 100644
--- a/editors/sed.c
+++ b/editors/sed.c
@@ -657,9 +657,8 @@ static void add_cmd(const char *cmdstr)
 
         /* Append this line to any unfinished line from last time. */
         if (G.add_cmd_line) {
-                char *tp = xasprintf("%s\n%s", G.add_cmd_line, cmdstr);
-                free(G.add_cmd_line);
-                cmdstr = G.add_cmd_line = tp;
+                cmdstr = xasprintf_inplace(G.add_cmd_line,
+                        "%s\n%s", G.add_cmd_line, cmdstr);
         }
 
         /* If this line ends with unescaped backslash, request next line. */
diff --git a/include/libbb.h b/include/libbb.h
index 7cca925b9..6ce01ea94 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -950,6 +950,8 @@ int bb_putchar(int ch) FAST_FUNC;
 int bb_putchar_stderr(char ch) FAST_FUNC;
 int fputs_stdout(const char *s) FAST_FUNC;
 char *xasprintf(const char *format, ...) __attribute__ ((format(printf, 1, 2))) FAST_FUNC RETURNS_MALLOC;
+char *xasprintf_and_free(char *allocated, const char *format, ...) __attribute__ ((format(printf, 2, 3))) FAST_FUNC RETURNS_MALLOC;
+#define xasprintf_inplace(allocated, ...) ((allocated) = xasprintf_and_free((allocated), __VA_ARGS__))
 char *auto_string(char *str) FAST_FUNC;
 // gcc-4.1.1 still isn't good enough at optimizing it
 // (+200 bytes compared to macro)
diff --git a/libbb/xfuncs_printf.c b/libbb/xfuncs_printf.c
index 5d26e2bfa..ed10084b3 100644
--- a/libbb/xfuncs_printf.c
+++ b/libbb/xfuncs_printf.c
@@ -349,6 +349,22 @@ char* FAST_FUNC xasprintf(const char *format, ...)
         return string_ptr;
 }
 
+char* FAST_FUNC xasprintf_and_free(char *allocated, const char *format, ...)
+{
+        va_list p;
+        int r;
+        char *string_ptr;
+
+        va_start(p, format);
+        r = vasprintf(&string_ptr, format, p);
+        va_end(p);
+
+        if (r < 0)
+                bb_die_memory_exhausted();
+        free(allocated);
+        return string_ptr;
+}
+
 void FAST_FUNC xsetenv(const char *key, const char *value)
 {
         if (setenv(key, value, 1))
diff --git a/modutils/modprobe-small.c b/modutils/modprobe-small.c
index 31a215a29..b3c0768ee 100644
--- a/modutils/modprobe-small.c
+++ b/modutils/modprobe-small.c
@@ -1010,9 +1010,7 @@ int modprobe_main(int argc UNUSED_PARAM, char **argv)
                 char **arg = argv;
                 while (*++arg) {
                         /* Enclose options in quotes */
-                        char *s = options;
-                        options = xasprintf("%s \"%s\"", s ? s : "", *arg);
-                        free(s);
+                        xasprintf_inplace(options, "%s \"%s\"", options ? options : "", *arg);
                         *arg = NULL;
                 }
 # else
diff --git a/networking/ifupdown.c b/networking/ifupdown.c
index 9c3640be7..bc2dca506 100644
--- a/networking/ifupdown.c
+++ b/networking/ifupdown.c
@@ -895,16 +895,15 @@ static struct interfaces_file_t *read_interfaces(const char *filename, struct in
         while ((buf = xmalloc_fgetline(f)) != NULL) {
 #if ENABLE_DESKTOP
                 /* Trailing "\" concatenates lines */
+//TODO: check how to handle "line\\" (double backslashes)
                 char *p;
                 while ((p = last_char_is(buf, '\\')) != NULL) {
                         *p = '\0';
                         rest_of_line = xmalloc_fgetline(f);
                         if (!rest_of_line)
                                 break;
-                        p = xasprintf("%s%s", buf, rest_of_line);
-                        free(buf);
+                        xasprintf_inplace(buf, "%s%s", buf, rest_of_line);
                         free(rest_of_line);
-                        buf = p;
                 }
 #endif
                 rest_of_line = buf;
diff --git a/networking/netstat.c b/networking/netstat.c
index 807800a62..d7afa8fdd 100644
--- a/networking/netstat.c
+++ b/networking/netstat.c
@@ -391,7 +391,7 @@ static const char *get_sname(int port, const char *proto, int numeric)
 
 static char *ip_port_str(struct sockaddr *addr, int port, const char *proto, int numeric)
 {
-        char *host, *host_port;
+        char *host;
 
         /* Code which used "*" for INADDR_ANY is removed: it's ambiguous
          * in IPv6, while "0.0.0.0" is not. */
@@ -402,9 +402,8 @@ static char *ip_port_str(struct sockaddr *addr, int port, const char *proto, int
         if (!host)
                 host = xmalloc_sockaddr2dotted_noport(addr);
 
-        host_port = xasprintf("%s:%s", host, get_sname(htons(port), proto, numeric));
-        free(host);
-        return host_port;
+        xasprintf_inplace(host, "%s:%s", host, get_sname(htons(port), proto, numeric));
+        return host;
 }
 
 struct inet_params {
diff --git a/procps/watch.c b/procps/watch.c
index b376fdc33..b828079e5 100644
--- a/procps/watch.c
+++ b/procps/watch.c
@@ -76,12 +76,9 @@ int watch_main(int argc UNUSED_PARAM, char **argv)
         // watch ls -l "a /tmp" "2>&1" - ls won't see "a /tmp" as one param.
         argv0 = argv;
         // If -x, cmd is only used for printing header
-        cmd = *argv;
+        cmd = xstrdup(*argv);
         while (*++argv)
-                cmd = xasprintf("%s %s", cmd, *argv);
-//leaks cmd ^^^
-//TODO: create and use xasprintf_inplace(DST, fmt, args_one_of_which_is_DST)
-//which frees old DST?
+                xasprintf_inplace(cmd, "%s %s", cmd, *argv);
         if (opt & (1 << 3))
                 argv = argv0; // If -x, restore argv[0] to !NULL
 
diff --git a/util-linux/lsblk.c b/util-linux/lsblk.c
index a482bfbbc..3bd40bcb4 100644
--- a/util-linux/lsblk.c
+++ b/util-linux/lsblk.c
@@ -101,10 +101,10 @@ static char *get_mountpoints(const char *majmin)
 
         mountpoints = NULL;
         len = strlen(majmin);
-        p = G.mountinfo; // "/proc/self/mountinfo"
+        p = G.mountinfo; // contents of "/proc/self/mountinfo"
         /* lines a-la "63 1 259:3 / /MNTPOINT per-mount_options - ext4 /dev/NAME per-superblock_options" */
         while (*p) {
-                char *e, *f;
+                char *e;
 
                 p = skip_non_whitespace(p);
                 if (*p != ' ') break;
@@ -127,12 +127,11 @@ static char *get_mountpoints(const char *majmin)
                 // at " /MNTPOINT"
                 e = skip_non_whitespace(p + 1);
                 // e is at the end of " /MNTPOINT"
-                f = mountpoints;
 // NO. We return " /MNT1 /MNT2 /MNT3" _with_ leading space!
-//              if (!f)
+//              if (!mountpoints)
 //                      p++;
-                mountpoints = xasprintf("%s%.*s", f ? f : "", (int)(e - p), p);
-                free(f);
+                xasprintf_inplace(mountpoints, "%s%.*s",
+                        mountpoints ? mountpoints : "", (int)(e - p), p);
         }
         return mountpoints;
 }
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),