shells: do not frocibly enable test, echo and kill _applets_,

just build relevant source and use xxx_main functions.
build system: add a special case when we have exactly one applet enabled
(makes "true", "false", "basename" REALLY tiny).
getopt32: do not use stdio.

function                                             old     new   delta
getopt32                                            1385    1412     +27
make_device                                         1187    1200     +13
basename_main                                        120     127      +7
tcpudpsvd_main                                      1922    1926      +4
testcmd                                                5       -      -5
echocmd                                                5       -      -5
fuser_main                                          1243    1231     -12
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 4/1 up/down: 51/-22)             Total: 29 bytes

1 files changed, 40 insertions, 2 deletions

diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index e2bb37868..a48a26003 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -36,6 +36,13 @@ static const char usage_messages[] ALIGN1 = ""
 
 /* Include generated applet names, pointers to <applet>_main, etc */
 #include "applet_tables.h"
+/* ...and if applet_tables generator says we have only one applet... */
+#ifdef SINGLE_APPLET_MAIN
+#undef ENABLE_FEATURE_INDIVIDUAL
+#define ENABLE_FEATURE_INDIVIDUAL 1
+#undef USE_FEATURE_INDIVIDUAL
+#define USE_FEATURE_INDIVIDUAL(...) __VA_ARGS__
+#endif
 
 
 #if ENABLE_FEATURE_COMPRESS_USAGE
@@ -77,6 +84,23 @@ static const char *unpack_usage_messages(void)
 void bb_show_usage(void)
 {
         if (ENABLE_SHOW_USAGE) {
+#ifdef SINGLE_APPLET_STR
+                /* Imagine that this applet is "true". Dont suck in printf! */
+                const char *p;
+                const char *usage_string = p = unpack_usage_messages();
+
+                if (*p == '\b') {
+                        write(2, "\nNo help available.\n\n",
+                                sizeof("\nNo help available.\n\n") - 1);
+                } else {
+                        write(2, "\nUsage: "SINGLE_APPLET_STR" ",
+                                sizeof("\nUsage: "SINGLE_APPLET_STR" ") - 1);
+                        write(2, p, strlen(p));
+                        write(2, "\n\n", 2);
+                }
+                dealloc_usage_messages((char*)usage_string);
+#else
+// TODO: in this case, stdio is sucked in by busybox_main() anyway...
                 const char *format_string;
                 const char *p;
                 const char *usage_string = p = unpack_usage_messages();
@@ -84,18 +108,17 @@ void bb_show_usage(void)
 
                 if (ap < 0) /* never happens, paranoia */
                         xfunc_die();
-
                 while (ap) {
                         while (*p++) continue;
                         ap--;
                 }
-
                 fprintf(stderr, "%s multi-call binary\n", bb_banner);
                 format_string = "\nUsage: %s %s\n\n";
                 if (*p == '\b')
                         format_string = "\nNo help available.\n\n";
                 fprintf(stderr, format_string, applet_name, p);
                 dealloc_usage_messages((char*)usage_string);
+#endif
         }
         xfunc_die();
 }
@@ -125,6 +148,9 @@ int *const bb_errno __attribute__ ((section (".data")));
 
 void lbb_prepare(const char *applet
                 USE_FEATURE_INDIVIDUAL(, char **argv))
+                                MAIN_EXTERNALLY_VISIBLE;
+void lbb_prepare(const char *applet
+                USE_FEATURE_INDIVIDUAL(, char **argv))
 {
 #ifdef __GLIBC__
         (*(int **)&bb_errno) = __errno_location();
@@ -158,6 +184,9 @@ const char *applet_name;
 bool re_execed;
 #endif
 
+
+#if !ENABLE_FEATURE_INDIVIDUAL
+
 USE_FEATURE_SUID(static uid_t ruid;)  /* real uid */
 
 #if ENABLE_FEATURE_SUID_CONFIG
@@ -660,6 +689,9 @@ void run_applet_and_exit(const char *name, char **argv)
                 exit(busybox_main(argv));
 }
 
+#endif /* !ENABLE_FEATURE_INDIVIDUAL */
+
+
 
 #if ENABLE_BUILD_LIBBUSYBOX
 int lbb_main(char **argv)
@@ -667,6 +699,11 @@ int lbb_main(char **argv)
 int main(int argc ATTRIBUTE_UNUSED, char **argv)
 #endif
 {
+#if ENABLE_FEATURE_INDIVIDUAL
+        /* Only one applet is selected by the user! */
+        lbb_prepare(SINGLE_APPLET_STR USE_FEATURE_INDIVIDUAL(, argv));
+        return SINGLE_APPLET_MAIN(argc, argv);
+#else
         lbb_prepare("busybox" USE_FEATURE_INDIVIDUAL(, argv));
 
 #if !BB_MMU
@@ -685,4 +722,5 @@ int main(int argc ATTRIBUTE_UNUSED, char **argv)
 
         run_applet_and_exit(applet_name, argv);
         bb_error_msg_and_die("applet not found");
+#endif
 }