libbb: reduce the overhead of single parameter bb_error_msg() calls

Back in 2007, commit 0c97c9d43707 ("'simple' error message functions by
Loic Grenie") introduced bb_simple_perror_msg() to allow for a lower
overhead call to bb_perror_msg() when only a string was being printed
with no parameters. This saves space for some CPU architectures because
it avoids the overhead of a call to a variadic function. However there
has never been a simple version of bb_error_msg(), and since 2007 many
new calls to bb_perror_msg() have been added that only take a single
parameter and so could have been using bb_simple_perror_message().

This changeset introduces 'simple' versions of bb_info_msg(),
bb_error_msg(), bb_error_msg_and_die(), bb_herror_msg() and
bb_herror_msg_and_die(), and replaces all calls that only take a
single parameter, or use something like ("%s", arg), with calls to the
corresponding 'simple' version.

Since it is likely that single parameter calls to the variadic functions
may be accidentally reintroduced in the future a new debugging config
option WARN_SIMPLE_MSG has been introduced. This uses some macro magic
which will cause any such calls to generate a warning, but this is
turned off by default to avoid use of the unpleasant macros in normal
circumstances.

This is a large changeset due to the number of calls that have been
replaced. The only files that contain changes other than simple
substitution of function calls are libbb.h, libbb/herror_msg.c,
libbb/verror_msg.c and libbb/xfuncs_printf.c. In miscutils/devfsd.c,
networking/udhcp/common.h and util-linux/mdev.c additonal macros have
been added for logging so that single parameter and multiple parameter
logging variants exist.

The amount of space saved varies considerably by architecture, and was
found to be as follows (for 'defconfig' using GCC 7.4):

Arm:     -92 bytes
MIPS:    -52 bytes
PPC:   -1836 bytes
x86_64: -938 bytes

Note that for the MIPS architecture only an exception had to be made
disabling the 'simple' calls for 'udhcp' (in networking/udhcp/common.h)
because it made these files larger on MIPS.

Signed-off-by: James Byrne <james.byrne@origamienergy.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 44 insertions, 1 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 021100d..111d1b7 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1137,7 +1137,7 @@ void exec_prog_or_SHELL(char **argv) NORETURN FAST_FUNC;
 ({ \
 	pid_t bb__xvfork_pid = vfork(); \
 	if (bb__xvfork_pid < 0) \
-		bb_perror_msg_and_die("vfork"); \
+		bb_simple_perror_msg_and_die("vfork"); \
 	bb__xvfork_pid; \
 })
 #if BB_MMU
@@ -1324,13 +1324,17 @@ extern void (*die_func)(void);
 void xfunc_die(void) NORETURN FAST_FUNC;
 void bb_show_usage(void) NORETURN FAST_FUNC;
 void bb_error_msg(const char *s, ...) __attribute__ ((format (printf, 1, 2))) FAST_FUNC;
+void bb_simple_error_msg(const char *s) FAST_FUNC;
 void bb_error_msg_and_die(const char *s, ...) __attribute__ ((noreturn, format (printf, 1, 2))) FAST_FUNC;
+void bb_simple_error_msg_and_die(const char *s) NORETURN FAST_FUNC;
 void bb_perror_msg(const char *s, ...) __attribute__ ((format (printf, 1, 2))) FAST_FUNC;
 void bb_simple_perror_msg(const char *s) FAST_FUNC;
 void bb_perror_msg_and_die(const char *s, ...) __attribute__ ((noreturn, format (printf, 1, 2))) FAST_FUNC;
 void bb_simple_perror_msg_and_die(const char *s) NORETURN FAST_FUNC;
 void bb_herror_msg(const char *s, ...) __attribute__ ((format (printf, 1, 2))) FAST_FUNC;
+void bb_simple_herror_msg(const char *s) FAST_FUNC;
 void bb_herror_msg_and_die(const char *s, ...) __attribute__ ((noreturn, format (printf, 1, 2))) FAST_FUNC;
+void bb_simple_herror_msg_and_die(const char *s) NORETURN FAST_FUNC;
 void bb_perror_nomsg_and_die(void) NORETURN FAST_FUNC;
 void bb_perror_nomsg(void) FAST_FUNC;
 void bb_verror_msg(const char *s, va_list p, const char *strerr) FAST_FUNC;
@@ -1339,12 +1343,51 @@ void bb_logenv_override(void) FAST_FUNC;
 
 #if ENABLE_FEATURE_SYSLOG_INFO
 void bb_info_msg(const char *s, ...) __attribute__ ((format (printf, 1, 2))) FAST_FUNC;
+void bb_simple_info_msg(const char *s) FAST_FUNC;
 void bb_vinfo_msg(const char *s, va_list p) FAST_FUNC;
 #else
 #define bb_info_msg bb_error_msg
+#define bb_simple_info_msg bb_simple_error_msg
 #define bb_vinfo_msg(s,p) bb_verror_msg(s,p,NULL)
 #endif
 
+#if ENABLE_WARN_SIMPLE_MSG
+/* If enabled, cause calls to bb_error_msg() et al that only take a single
+ * parameter to generate a warning.
+ */
+static inline void __attribute__ ((deprecated("use bb_simple_error_msg instead")))
+	bb_not_simple_error_msg(const char *s) { bb_simple_error_msg(s); }
+static inline void __attribute__ ((deprecated("use bb_simple_error_msg_and_die instead"))) NORETURN
+	bb_not_simple_error_msg_and_die(const char *s) { bb_simple_error_msg_and_die(s); }
+static inline void __attribute__ ((deprecated("use bb_simple_perror_msg instead")))
+	bb_not_simple_perror_msg(const char *s) { bb_simple_perror_msg(s); }
+static inline void __attribute__ ((deprecated("use bb_simple_perror_msg_and_die instead"))) NORETURN
+	bb_not_simple_perror_msg_and_die(const char *s) { bb_simple_perror_msg_and_die(s); }
+static inline void __attribute__ ((deprecated("use bb_simple_herror_msg instead")))
+	bb_not_simple_herror_msg(const char *s) { bb_simple_herror_msg(s); }
+static inline void __attribute__ ((deprecated("use bb_simple_herror_msg_and_die instead"))) NORETURN
+	bb_not_simple_herror_msg_and_die(const char *s) { bb_simple_herror_msg_and_die(s); }
+static inline void __attribute__ ((deprecated("use bb_simple_info_msg instead")))
+	bb_not_simple_info_msg(const char *s) { bb_simple_info_msg(s); }
+/* Override bb_error_msg() and related functions with macros that will
+ * substitute them for the equivalent bb_not_simple_error_msg() function when
+ * they are used with only a single parameter. Macro approach inspired by
+ * https://gustedt.wordpress.com/2010/06/08/detect-empty-macro-arguments and
+ * https://gustedt.wordpress.com/2010/06/03/default-arguments-for-c99
+ */
+#define _ARG18(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, _17, ...) _17
+#define BB_MSG_KIND(...)           _ARG18(__VA_ARGS__, , , , , , , , , , , , , , , , , _not_simple)
+#define _BB_MSG(name, kind, ...)   bb##kind##name(__VA_ARGS__)
+#define BB_MSG(name, kind, ...)    _BB_MSG(name, kind, __VA_ARGS__)
+#define bb_error_msg(...)          BB_MSG(_error_msg, BB_MSG_KIND(__VA_ARGS__), __VA_ARGS__)
+#define bb_error_msg_and_die(...)  BB_MSG(_error_msg_and_die, BB_MSG_KIND(__VA_ARGS__), __VA_ARGS__)
+#define bb_perror_msg(...)         BB_MSG(_perror_msg, BB_MSG_KIND(__VA_ARGS__), __VA_ARGS__)
+#define bb_perror_msg_and_die(...) BB_MSG(_perror_msg_and_die, BB_MSG_KIND(__VA_ARGS__), __VA_ARGS__)
+#define bb_herror_msg(...)         BB_MSG(_herror_msg, BB_MSG_KIND(__VA_ARGS__), __VA_ARGS__)
+#define bb_herror_msg_and_die(...) BB_MSG(_herror_msg_and_die, BB_MSG_KIND(__VA_ARGS__), __VA_ARGS__)
+#define bb_info_msg(...)           BB_MSG(_info_msg, BB_MSG_KIND(__VA_ARGS__), __VA_ARGS__)
+#endif
+
 /* We need to export XXX_main from libbusybox
  * only if we build "individual" binaries
  */