ash: optional printf builtin. +25 bytes if off, +35 if on.

by Cristian Ionescu-Idbohrn.

coreutils/Kbuild

@@ -54,6 +54,7 @@ lib-$(CONFIG_NOHUP)     += nohup.o
 lib-$(CONFIG_OD)        += od.o
 lib-$(CONFIG_PRINTENV)  += printenv.o
 lib-$(CONFIG_PRINTF)    += printf.o
+lib-$(CONFIG_ASH_BUILTIN_PRINTF) += printf.o
 lib-$(CONFIG_PWD)       += pwd.o
 lib-$(CONFIG_READLINK)  += readlink.o
 lib-$(CONFIG_REALPATH)  += realpath.o

coreutils/chown.c

@@ -61,7 +61,6 @@ static int fileAction(const char *fileName, struct stat *statbuf,
 	return FALSE;
 }
 
-int chown_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int chown_main(int argc ATTRIBUTE_UNUSED, char **argv)
 {
 	int retval = EXIT_SUCCESS;

coreutils/printf.c

@@ -193,6 +193,7 @@ static char **print_formatted(char *f, char **argv)
 	unsigned direc_length;  /* Length of % directive.  */
 	int field_width;        /* Arg to first '*', or -1 if none.  */
 	int precision;          /* Arg to second '*', or -1 if none.  */
+	char **saved_argv = argv;
 
 	for (; *f; ++f) {
 		switch (*f) {
@@ -264,8 +265,9 @@ static char **print_formatted(char *f, char **argv)
 							precision, "");
 			break;
 		case '\\':
-			if (*++f == 'c')
+			if (*++f == 'c') {
-				exit(EXIT_SUCCESS);
+				return saved_argv; /* causes main() to exit */
+			}
 			bb_putchar(bb_process_escape_sequence((const char **)&f));
 			f--;
 			break;
@@ -277,12 +279,22 @@ static char **print_formatted(char *f, char **argv)
 	return argv;
 }
 
-int printf_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int printf_main(int argc ATTRIBUTE_UNUSED, char **argv)
 {
 	char *format;
 	char **argv2;
 
+	/* We must check that stdout is not closed.
+	 * The reason for this is highly non-obvious. printf_main is used from shell.
+	 * Shell must correctly handle 'printf "%s" foo'
+	 * if stdout is closed. With stdio, output gets shoveled into
+	 * stdout buffer, and even fflush cannot clear it out. It seems that
+	 * even if libc receives EBADF on write attempts, it feels determined
+	 * to output data no matter what. So it will try later,
+	 * and possibly will clobber future output. Not good. */
+	if (dup2(1, 1) != 1)
+		return -1;
+
 	/* bash builtin errors out on "printf '-%s-\n' foo",
 	 * coreutils-6.9 works. Both work with "printf -- '-%s-\n' foo".
 	 * We will mimic coreutils. */

include/applets.h

@@ -275,7 +275,7 @@ USE_PIVOT_ROOT(APPLET(pivot_root, _BB_DIR_SBIN, _BB_SUID_NEVER))
 USE_PKILL(APPLET_ODDNAME(pkill, pgrep, _BB_DIR_USR_BIN, _BB_SUID_NEVER, pkill))
 USE_HALT(APPLET_ODDNAME(poweroff, halt, _BB_DIR_SBIN, _BB_SUID_NEVER, poweroff))
 USE_PRINTENV(APPLET(printenv, _BB_DIR_BIN, _BB_SUID_NEVER))
-USE_PRINTF(APPLET(printf, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
+USE_PRINTF(APPLET_NOFORK(printf, printf, _BB_DIR_USR_BIN, _BB_SUID_NEVER, printf))
 USE_PS(APPLET(ps, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_PSCAN(APPLET(pscan, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_PWD(APPLET_NOFORK(pwd, pwd, _BB_DIR_BIN, _BB_SUID_NEVER, pwd))

include/libbb.h

@@ -878,13 +878,16 @@ extern void bb_verror_msg(const char *s, va_list p, const char *strerr);
 #endif
 
 
-/* applets which are useful from another applets */
+/* Applets which are useful from another applets */
 int bb_cat(char** argv);
-/* If shell needs them, these three "exist" even if not enabled as applets */
+/* If shell needs them, they exist even if not enabled as applets */
 int echo_main(int argc, char** argv) USE_ECHO(MAIN_EXTERNALLY_VISIBLE);
+int printf_main(int argc, char **argv) USE_PRINTF(MAIN_EXTERNALLY_VISIBLE);
 int test_main(int argc, char **argv) USE_TEST(MAIN_EXTERNALLY_VISIBLE);
 int kill_main(int argc, char **argv) USE_KILL(MAIN_EXTERNALLY_VISIBLE);
-int chown_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+/* Similar, but used by chgrp, not shell */
+int chown_main(int argc, char **argv) USE_CHOWN(MAIN_EXTERNALLY_VISIBLE);
+/* Don't need USE_xxx() guard for these */
 int gunzip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int bunzip2_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int bbunpack(char **argv,

miscutils/last.c

@@ -10,6 +10,9 @@
 #include "libbb.h"
 #include <utmp.h>
 
+/* NB: ut_name and ut_user are the same field, use only one name (ut_user)
+ * to reduce confusion */
+
 #ifndef SHUTDOWN_TIME
 #  define SHUTDOWN_TIME 254
 #endif

miscutils/last_fancy.c

@@ -10,6 +10,9 @@
 #include "libbb.h"
 #include <utmp.h>
 
+/* NB: ut_name and ut_user are the same field, use only one name (ut_user)
+ * to reduce confusion */
+
 #ifndef SHUTDOWN_TIME
 #  define SHUTDOWN_TIME 254
 #endif

shell/Config.in

@@ -114,6 +114,13 @@ config ASH_BUILTIN_ECHO
 	help
 	  Enable support for echo, builtin to ash.
 
+config ASH_BUILTIN_PRINTF
+	bool "Builtin version of 'printf'"
+	default y
+	depends on ASH
+	help
+	  Enable support for printf, builtin to ash.
+
 config ASH_BUILTIN_TEST
 	bool "Builtin version of 'test'"
 	default y

shell/ash.c

@@ -8488,8 +8488,9 @@ static int ulimitcmd(int, char **);
  * Apart from the above, [[ expr ]] should work as [ expr ]
  */
 
-#define testcmd test_main
 #define echocmd   echo_main
+#define printfcmd printf_main
+#define testcmd   test_main
 
 /* Keep these in proper order since it is searched via bsearch() */
 static const struct builtincmd builtintab[] = {
@@ -8540,6 +8541,9 @@ static const struct builtincmd builtintab[] = {
 	{ BUILTIN_NOSPEC        "let", letcmd },
 #endif
 	{ BUILTIN_ASSIGN        "local", localcmd },
+#if ENABLE_ASH_BUILTIN_PRINTF
+	{ BUILTIN_REGULAR       "printf", printfcmd },
+#endif
 	{ BUILTIN_NOSPEC        "pwd", pwdcmd },
 	{ BUILTIN_REGULAR       "read", readcmd },
 	{ BUILTIN_SPEC_REG_ASSG "readonly", exportcmd },