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, 2 insertions, 0 deletions

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)