opt: add support for showing default value.

ccan/opt/helpers.c

@@ -5,6 +5,9 @@
 #include <stdio.h>
 #include "private.h"
 
+/* Upper bound to sprintf this simple type?  Each 3 bits < 1 digit. */
+#define CHAR_SIZE(type) (((sizeof(type)*CHAR_BIT + 2) / 3) + 1)
+
 /* FIXME: asprintf module? */
 static char *arg_bad(const char *fmt, const char *arg)
 {
@@ -116,7 +119,7 @@ char *opt_inc_intval(int *i)
 }
 
 /* Display version string. */
-char *opt_show_version_and_exit(const char *version)
+char *opt_version_and_exit(const char *version)
 {
 	printf("%s\n", version);
 	exit(0);
@@ -127,3 +130,44 @@ char *opt_usage_and_exit(const char *extra)
 	printf("%s", opt_usage(opt_argv0, extra));
 	exit(0);
 }
+
+void opt_show_bool(char buf[OPT_SHOW_LEN], const bool *b)
+{
+	strncpy(buf, *b ? "true" : "false", OPT_SHOW_LEN);
+}
+
+void opt_show_invbool(char buf[OPT_SHOW_LEN], const bool *b)
+{
+	strncpy(buf, *b ? "false" : "true", OPT_SHOW_LEN);
+}
+
+void opt_show_charp(char buf[OPT_SHOW_LEN], char *const *p)
+{
+	size_t len = strlen(*p);
+	buf[0] = '"';
+	if (len > OPT_SHOW_LEN - 2)
+		len = OPT_SHOW_LEN - 2;
+	strncpy(buf+1, *p, len);
+	buf[1+len] = '"';
+}
+
+/* Set an integer value, various forms.  Sets to 1 on arg == NULL. */
+void opt_show_intval(char buf[OPT_SHOW_LEN], const int *i)
+{
+	snprintf(buf, OPT_SHOW_LEN, "%i", *i);
+}
+
+void opt_show_uintval(char buf[OPT_SHOW_LEN], const unsigned int *ui)
+{
+	snprintf(buf, OPT_SHOW_LEN, "%u", *ui);
+}
+
+void opt_show_longval(char buf[OPT_SHOW_LEN], const long *l)
+{
+	snprintf(buf, OPT_SHOW_LEN, "%li", *l);
+}
+
+void opt_show_ulongval(char buf[OPT_SHOW_LEN], const unsigned long *ul)
+{
+	snprintf(buf, OPT_SHOW_LEN, "%lu", *ul);
+}

ccan/opt/opt.c

@@ -31,6 +31,7 @@ static void add_opt(const struct opt_table *entry)
 void _opt_register(const char *longopt, char shortopt, enum opt_flags flags,
 		   char *(*cb)(void *arg),
 		   char *(*cb_arg)(const char *optarg, void *arg),
+		   void (*show)(char buf[OPT_SHOW_LEN], const void *arg),
 		   void *arg, const char *desc)
 {
 	struct opt_table opt;
@@ -39,6 +40,7 @@ void _opt_register(const char *longopt, char shortopt, enum opt_flags flags,
 	opt.flags = flags;
 	opt.cb = cb;
 	opt.cb_arg = cb_arg;
+	opt.show = show;
 	opt.arg = arg;
 	opt.desc = desc;
 	check_opt(&opt);

ccan/opt/opt.h

@@ -12,12 +12,16 @@ enum opt_flags {
 	OPT_END = 8,		/* End of the table. */
 };
 
+/* Maximum length of arg to show in opt_usage */
+#define OPT_SHOW_LEN 80
+
 struct opt_table {
 	const char *longopt; /* --longopt, or NULL */
 	char shortopt; /* -s, or 0 */
 	enum opt_flags flags;
 	char *(*cb)(void *arg); /* OPT_NOARG */
 	char *(*cb_arg)(const char *optarg, void *arg); /* OPT_HASARG */
+	void (*show)(char buf[OPT_SHOW_LEN], const void *arg);
 	void *arg;
 	const char *desc;
 };
@@ -48,22 +52,28 @@ struct opt_table {
  * @longopt: the name of the argument (eg. "foo" for "--foo <arg>"), or NULL.
  * @shortopt: the character of the argument (eg. 'f' for "-f <arg>"), or 0.
  * @cb: the callback when the option is found (along with <arg>).
- * @arg: the argument to hand to @cb.
+ * @show: the callback to print the value in get_usage (or NULL)
+ * @arg: the argument to hand to @cb and @show
  *
  * This is a typesafe wrapper for intializing a struct opt_table.  The callback
- * is of type "bool cb(const char *, type *)",
- * "bool cb(const char *, const type *)" or "bool cb(const char *, void *)",
+ * is of type "char *cb(const char *, type *)",
+ * "char *cb(const char *, const type *)" or "char *cb(const char *, void *)",
  * where "type" is the type of the @arg argument.  The first argument to the
  * @cb is the argument found on the commandline.
  *
+ * Similarly, if @show is not NULL, it should be of type "void *show(char *,
+ * const type *)".  It should write up to OPT_SHOW_LEN bytes into the first
+ * argument; unless it uses the entire OPT_SHOW_LEN bytes it should
+ * nul-terminate that buffer.
+ *
  * At least one of @longopt and @shortopt must be non-zero.  If the
  * @cb returns false, opt_parse() will stop parsing and return false.
  *
  * See Also:
- *	OPT_WITH_ARG()
+ *	OPT_WITHOUT_ARG()
  */
-#define OPT_WITH_ARG(longopt, shortopt, cb, arg)	\
-	(longopt), (shortopt), OPT_CB_ARG((cb), (arg))
+#define OPT_WITH_ARG(longopt, shortopt, cb, show, arg)	\
+	(longopt), (shortopt), OPT_CB_ARG((cb), (show), (arg))
 
 /**
  * OPT_SUBTABLE() - macro for including another table inside a table.
@@ -74,7 +84,7 @@ struct opt_table {
  */
 #define OPT_SUBTABLE(table, desc)					\
 	{ (const char *)(table), sizeof(_check_is_entry(table)),	\
-	  OPT_SUBTABLE,	NULL, NULL, NULL, (desc) }
+	OPT_SUBTABLE,	NULL, NULL, NULL, NULL, (desc) }
 
 /**
  * opt_table_hidden - string for undocumented option tables.
@@ -125,8 +135,8 @@ void opt_register_table(const struct opt_table table[], const char *desc);
  * This is used for registering a single commandline option which takes
  * no argument.
  *
- * The callback is of type "bool cb(type *)", "bool cb(const type *)"
- * or "bool cb(void *)", where "type" is the type of the @arg
+ * The callback is of type "char *cb(type *)", "char *cb(const type *)"
+ * or "char *cb(void *)", where "type" is the type of the @arg
  * argument.
  *
  * At least one of @longopt and @shortopt must be non-zero.  If the
@@ -140,14 +150,15 @@ void opt_register_table(const struct opt_table table[], const char *desc);
  * @longopt: the name of the argument (eg. "foo" for "--foo"), or NULL.
  * @shortopt: the character of the argument (eg. 'f' for "-f"), or 0.
  * @cb: the callback when the option is found.
+ * @show: the callback when the option is found.
  * @arg: the argument to hand to @cb.
  * @desc: the verbose desction of the option (for opt_usage()), or NULL.
  *
  * This is used for registering a single commandline option which takes
  * an argument.
  *
- * The callback is of type "bool cb(const char *, type *)",
- * "bool cb(const char *, const type *)" or "bool cb(const char *, void *)",
+ * The callback is of type "char *cb(const char *, type *)",
+ * "char *cb(const char *, const type *)" or "char *cb(const char *, void *)",
  * where "type" is the type of the @arg argument.  The first argument to the
  * @cb is the argument found on the commandline.
  *
@@ -158,8 +169,8 @@ void opt_register_table(const struct opt_table table[], const char *desc);
  *	opt_register_arg("explode", 'e', explode_cb, NULL,
  *			 "Make the machine explode (developers only)");
  */
-#define opt_register_arg(longopt, shortopt, cb, arg, desc)	\
-	_opt_register((longopt), (shortopt), OPT_CB_ARG((cb), (arg)), (desc))
+#define opt_register_arg(longopt, shortopt, cb, show, arg, desc)	\
+   _opt_register((longopt), (shortopt), OPT_CB_ARG((cb), (show), (arg)), (desc))
 
 /**
  * opt_parse - parse arguments.
@@ -216,24 +227,32 @@ char *opt_usage(const char *argv0, const char *extra);
 char *opt_set_bool(bool *b);
 /* Sets @b based on arg: (yes/no/true/false). */
 char *opt_set_bool_arg(const char *arg, bool *b);
+void opt_show_bool(char buf[OPT_SHOW_LEN], const bool *b);
 /* The inverse */
 char *opt_set_invbool(bool *b);
+void opt_show_invbool(char buf[OPT_SHOW_LEN], const bool *b);
+/* Sets @b based on !arg: (yes/no/true/false). */
 char *opt_set_invbool_arg(const char *arg, bool *b);
 
 /* Set a char *. */
 char *opt_set_charp(const char *arg, char **p);
+void opt_show_charp(char buf[OPT_SHOW_LEN], char *const *p);
 
 /* Set an integer value, various forms.  Sets to 1 on arg == NULL. */
 char *opt_set_intval(const char *arg, int *i);
+void opt_show_intval(char buf[OPT_SHOW_LEN], const int *i);
 char *opt_set_uintval(const char *arg, unsigned int *ui);
+void opt_show_uintval(char buf[OPT_SHOW_LEN], const unsigned int *ui);
 char *opt_set_longval(const char *arg, long *l);
+void opt_show_longval(char buf[OPT_SHOW_LEN], const long *l);
 char *opt_set_ulongval(const char *arg, unsigned long *ul);
+void opt_show_ulongval(char buf[OPT_SHOW_LEN], const unsigned long *ul);
 
 /* Increment. */
 char *opt_inc_intval(int *i);
 
 /* Display version string to stdout, exit(0). */
-char *opt_show_version_and_exit(const char *version);
+char *opt_version_and_exit(const char *version);
 
 /* Display usage string to stdout, exit(0). */
 char *opt_usage_and_exit(const char *extra);
@@ -245,22 +264,25 @@ char *opt_usage_and_exit(const char *extra);
 	cast_if_any(char *(*)(void *), (cb), &*(cb),	\
 		    char *(*)(typeof(*(arg))*),		\
 		    char *(*)(const typeof(*(arg))*),	\
-		    char *(*)(const typeof(*(arg))*)),	\
-	NULL, (arg)
+		    char *(*)(const void *)),		\
+	NULL, NULL, (arg)
 
 /* Resolves to the four parameters for arg callbacks. */
-#define OPT_CB_ARG(cb, arg)						\
+#define OPT_CB_ARG(cb, show, arg)					\
 	OPT_HASARG, NULL,						\
 	cast_if_any(char *(*)(const char *,void *), (cb), &*(cb),	\
 		    char *(*)(const char *, typeof(*(arg))*),		\
 		    char *(*)(const char *, const typeof(*(arg))*),	\
-		    char *(*)(const char *, const typeof(*(arg))*)),	\
+		    char *(*)(const char *, const void *)),		\
+	cast_if_type(void (*)(char buf[], const void *), (show), &*(show), \
+		     void (*)(char buf[], const typeof(*(arg))*)),	\
 	(arg)
 
 /* Non-typesafe register function. */
 void _opt_register(const char *longopt, char shortopt, enum opt_flags flags,
 		   char *(*cb)(void *arg),
 		   char *(*cb_arg)(const char *optarg, void *arg),
+		   void (*show)(char buf[OPT_SHOW_LEN], const void *arg),
 		   void *arg, const char *desc);
 
 /* We use this to get typechecking for OPT_SUBTABLE */

ccan/opt/test/run-helpers.c

+#define _GNU_SOURCE
+#include <stdio.h>
+#include <ccan/tap/tap.h>
+#include <setjmp.h>
+#include <stdlib.h>
+#include "utils.h"
+
+/* We don't actually want it to exit... */
+static jmp_buf exited;
+#define exit(status) longjmp(exited, (status) + 1)
+
+#define printf saved_printf
+static int saved_printf(const char *fmt, ...);
+
+#include <ccan/opt/helpers.c>
+#include <ccan/opt/opt.c>
+#include <ccan/opt/usage.c>
+
+static void reset_options(void)
+{
+	free(opt_table);
+	opt_table = NULL;
+	opt_count = 0;
+}
+
+static char *output = NULL;
+
+static int saved_printf(const char *fmt, ...)
+{
+	va_list ap;
+	char *p;
+	int ret;
+
+	va_start(ap, fmt);
+	ret = vasprintf(&p, fmt, ap);
+	va_end(ap);
+
+	if (output) {
+		output = realloc(output, strlen(output) + strlen(p) + 1);
+		strcat(output, p);
+		free(p);
+	} else
+		output = p;
+
+	return ret;
+}	
+
+/* Test helpers. */
+int main(int argc, char *argv[])
+{
+	plan_tests(88);
+
+	/* opt_set_bool */
+	{
+		bool arg = false;
+		reset_options();
+		opt_register_noarg(NULL, 'a', opt_set_bool, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", NULL));
+		ok1(arg);
+		opt_register_arg(NULL, 'b', opt_set_bool_arg, NULL, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-b", "no", NULL));
+		ok1(!arg);
+		ok1(parse_args(&argc, &argv, "-b", "yes", NULL));
+		ok1(arg);
+		ok1(parse_args(&argc, &argv, "-b", "false", NULL));
+		ok1(!arg);
+		ok1(parse_args(&argc, &argv, "-b", "true", NULL));
+		ok1(arg);
+	}
+	/* opt_set_invbool */
+	{
+		bool arg = true;
+		reset_options();
+		opt_register_noarg(NULL, 'a', opt_set_invbool, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", NULL));
+		ok1(!arg);
+		opt_register_arg(NULL, 'b', opt_set_invbool_arg, NULL,
+				 &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-b", "no", NULL));
+		ok1(arg);
+		ok1(parse_args(&argc, &argv, "-b", "yes", NULL));
+		ok1(!arg);
+		ok1(parse_args(&argc, &argv, "-b", "false", NULL));
+		ok1(arg);
+		ok1(parse_args(&argc, &argv, "-b", "true", NULL));
+		ok1(!arg);
+	}
+	/* opt_set_charp */
+	{
+		char *arg = (char *)"wrong";
+		reset_options();
+		opt_register_arg(NULL, 'a', opt_set_charp, NULL, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", "string", NULL));
+		ok1(strcmp(arg, "string") == 0);
+	}
+	/* opt_set_intval */
+	{
+		int arg = 1000;
+		reset_options();
+		opt_register_arg(NULL, 'a', opt_set_intval, NULL, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", "9999", NULL));
+		ok1(arg == 9999);
+		ok1(parse_args(&argc, &argv, "-a", "-9999", NULL));
+		ok1(arg == -9999);
+		ok1(parse_args(&argc, &argv, "-a", "0", NULL));
+		ok1(arg == 0);
+		ok1(!parse_args(&argc, &argv, "-a", "100crap", NULL));
+		if (sizeof(int) == 4)
+			ok1(!parse_args(&argc, &argv, "-a", "4294967296", NULL));
+		else
+			fail("Handle other int sizes");
+	}
+	/* opt_set_uintval */
+	{
+		unsigned int arg = 1000;
+		reset_options();
+		opt_register_arg(NULL, 'a', opt_set_uintval, NULL, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", "9999", NULL));
+		ok1(arg == 9999);
+		ok1(!parse_args(&argc, &argv, "-a", "-9999", NULL));
+		ok1(parse_args(&argc, &argv, "-a", "0", NULL));
+		ok1(arg == 0);
+		ok1(!parse_args(&argc, &argv, "-a", "100crap", NULL));
+		ok1(!parse_args(&argc, &argv, "-a", "4294967296", NULL));
+	}
+	/* opt_set_longval */
+	{
+		long int arg = 1000;
+		reset_options();
+		opt_register_arg(NULL, 'a', opt_set_longval, NULL, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", "9999", NULL));
+		ok1(arg == 9999);
+		ok1(parse_args(&argc, &argv, "-a", "-9999", NULL));
+		ok1(arg == -9999);
+		ok1(parse_args(&argc, &argv, "-a", "0", NULL));
+		ok1(arg == 0);
+		ok1(!parse_args(&argc, &argv, "-a", "100crap", NULL));
+		if (sizeof(long) == 4)
+			ok1(!parse_args(&argc, &argv, "-a", "4294967296", NULL));
+		else if (sizeof(long)== 8)
+			ok1(!parse_args(&argc, &argv, "-a", "18446744073709551616", NULL));
+		else
+			fail("FIXME: Handle other long sizes");
+	}
+	/* opt_set_ulongval */
+	{
+		unsigned long int arg = 1000;
+		reset_options();
+		opt_register_arg(NULL, 'a', opt_set_ulongval, NULL, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", "9999", NULL));
+		ok1(arg == 9999);
+		ok1(!parse_args(&argc, &argv, "-a", "-9999", NULL));
+		ok1(parse_args(&argc, &argv, "-a", "0", NULL));
+		ok1(arg == 0);
+		ok1(!parse_args(&argc, &argv, "-a", "100crap", NULL));
+		if (sizeof(long) == 4)
+			ok1(!parse_args(&argc, &argv, "-a", "4294967296", NULL));
+		else if (sizeof(long)== 8)
+			ok1(!parse_args(&argc, &argv, "-a", "18446744073709551616", NULL));
+		else
+			fail("FIXME: Handle other long sizes");
+	}
+	/* opt_inc_intval */
+	{
+		int arg = 1000;
+		reset_options();
+		opt_register_noarg(NULL, 'a', opt_inc_intval, &arg, NULL);
+		ok1(parse_args(&argc, &argv, "-a", NULL));
+		ok1(arg == 1001);
+		ok1(parse_args(&argc, &argv, "-a", "-a", NULL));
+		ok1(arg == 1003);
+		ok1(parse_args(&argc, &argv, "-aa", NULL));
+		ok1(arg == 1005);
+	}
+
+	/* opt_show_version_and_exit. */
+	{
+		int exitval;
+		reset_options();
+		opt_register_noarg(NULL, 'a',
+				   opt_version_and_exit, "1.2.3", NULL);
+		exitval = setjmp(exited);
+		if (exitval == 0) {
+			parse_args(&argc, &argv, "-a", NULL);
+			fail("opt_show_version_and_exit returned?");
+		} else {
+			ok1(exitval - 1 == 0);
+		}
+		ok1(strcmp(output, "1.2.3\n") == 0);
+		free(output);
+		output = NULL;
+	}
+
+	/* opt_usage_and_exit. */
+	{
+		int exitval;
+		reset_options();
+		opt_register_noarg(NULL, 'a',
+				   opt_usage_and_exit, "[args]", NULL);
+		exitval = setjmp(exited);
+		if (exitval == 0) {
+			parse_args(&argc, &argv, "-a", NULL);
+			fail("opt_usage_and_exit returned?");
+		} else {
+			ok1(exitval - 1 == 0);
+		}
+		ok1(strstr(output, "[args]"));
+		ok1(strstr(output, argv[0]));
+		ok1(strstr(output, "[-a]"));
+		free(output);
+		output = NULL;
+	}
+
+	/* opt_show_bool */
+	{
+		bool b;
+		char buf[OPT_SHOW_LEN+2] = { 0 };
+		buf[OPT_SHOW_LEN] = '!';
+
+		b = true;
+		opt_show_bool(buf, &b);
+		ok1(strcmp(buf, "true") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+
+		b = false;
+		opt_show_bool(buf, &b);
+		ok1(strcmp(buf, "false") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+	}
+
+	/* opt_show_invbool */
+	{
+		bool b;
+		char buf[OPT_SHOW_LEN+2] = { 0 };
+		buf[OPT_SHOW_LEN] = '!';
+
+		b = true;
+		opt_show_invbool(buf, &b);
+		ok1(strcmp(buf, "false") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+
+		b = false;
+		opt_show_invbool(buf, &b);
+		ok1(strcmp(buf, "true") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+	}
+
+	/* opt_show_charp */
+	{
+		char str[OPT_SHOW_LEN*2], *p;
+		char buf[OPT_SHOW_LEN+2] = { 0 };
+		buf[OPT_SHOW_LEN] = '!';
+
+		/* Short test. */
+		p = str;
+		strcpy(p, "short");
+		opt_show_charp(buf, &p);
+		ok1(strcmp(buf, "\"short\"") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+
+		/* Truncate test. */
+		memset(p, 'x', OPT_SHOW_LEN*2);
+		p[OPT_SHOW_LEN*2-1] = '\0';
+		opt_show_charp(buf, &p);
+		ok1(buf[0] == '"');
+		ok1(buf[OPT_SHOW_LEN-1] == '"');
+		ok1(buf[OPT_SHOW_LEN] == '!');
+		ok1(strspn(buf+1, "x") == OPT_SHOW_LEN-2);
+	}
+
+	/* opt_show_intval */
+	{
+		int i;
+		char buf[OPT_SHOW_LEN+2] = { 0 };
+		buf[OPT_SHOW_LEN] = '!';
+
+		i = -77;
+		opt_show_intval(buf, &i);
+		ok1(strcmp(buf, "-77") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+
+		i = 77;
+		opt_show_intval(buf, &i);
+		ok1(strcmp(buf, "77") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+	}
+
+	/* opt_show_uintval */
+	{
+		unsigned int ui;
+		char buf[OPT_SHOW_LEN+2] = { 0 };
+		buf[OPT_SHOW_LEN] = '!';
+
+		ui = 4294967295U;
+		opt_show_uintval(buf, &ui);
+		ok1(strcmp(buf, "4294967295") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+	}
+
+	/* opt_show_longval */
+	{
+		long l;
+		char buf[OPT_SHOW_LEN+2] = { 0 };
+		buf[OPT_SHOW_LEN] = '!';
+
+		l = 1234567890L;
+		opt_show_longval(buf, &l);
+		ok1(strcmp(buf, "1234567890") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+	}
+
+	/* opt_show_ulongval */
+	{
+		unsigned long ul;
+		char buf[OPT_SHOW_LEN+2] = { 0 };
+		buf[OPT_SHOW_LEN] = '!';
+
+		ul = 4294967295UL;
+		opt_show_ulongval(buf, &ul);
+		ok1(strcmp(buf, "4294967295") == 0);
+		ok1(buf[OPT_SHOW_LEN] == '!');
+	}
+
+	return exit_status();
+}

ccan/opt/test/run-usage.c

@@ -19,7 +19,7 @@ int main(int argc, char *argv[])
 	char *output;
 	plan_tests(18);
 	opt_register_table(subtables, NULL);
-	opt_register_noarg("--kkk", 'k', my_cb, NULL, "magic kkk option");
+	opt_register_noarg("kkk", 'k', my_cb, NULL, "magic kkk option");
 	output = opt_usage("my name", "ExTrA Args");
 	diag("%s", output);
 	ok1(strstr(output, "Usage: my name"));
@@ -28,11 +28,11 @@ int main(int argc, char *argv[])
 	ok1(strstr(output, "-a "));
 	ok1(strstr(output, " Description of a\n"));
 	ok1(strstr(output, "-b <arg>"));
-	ok1(strstr(output, " Description of b\n"));
+	ok1(strstr(output, " Description of b (default: b)\n"));
 	ok1(strstr(output, "--ddd "));
 	ok1(strstr(output, " Description of ddd\n"));
 	ok1(strstr(output, "--eee <arg> "));
-	ok1(strstr(output, " Description of eee\n"));
+	ok1(strstr(output, " (default: eee)\n"));
 	ok1(strstr(output, "long table options:\n"));
 	/* This table is hidden. */
 	ok1(!strstr(output, "--ggg/-g "));

ccan/opt/test/run.c

@@ -54,7 +54,7 @@ int main(int argc, char *argv[])
 	/* Argument variants. */
 	reset_options();
 	test_cb_called = 0;
-	opt_register_arg("aaa", 'a', test_arg, "aaa", NULL);
+	opt_register_arg("aaa", 'a', test_arg, NULL, "aaa", NULL);
 	ok1(parse_args(&argc, &argv, "--aaa", "aaa", NULL));
 	ok1(argc == 1);
 	ok1(argv[0] == myname);

ccan/opt/test/utils.c

@@ -15,13 +15,18 @@ char *test_noarg(void *arg)
 	return NULL;
 }
 
-char *test_arg(const char *optarg, void *arg)
+char *test_arg(const char *optarg, const char *arg)
 {
 	test_cb_called++;
 	ok1(strcmp(optarg, arg) == 0);
 	return NULL;
 }
 
+void show_arg(char buf[OPT_SHOW_LEN], const char *arg)
+{
+	strncpy(buf, arg, OPT_SHOW_LEN);
+}
+
 char *err_output = NULL;
 
 static void save_err_output(const char *fmt, ...)
@@ -66,14 +71,14 @@ bool parse_args(int *argc, char ***argv, ...)
 struct opt_table short_table[] = {
 	/* Short opts, different args. */
 	{ OPT_WITHOUT_ARG(NULL, 'a', test_noarg, "a"), "Description of a" },
-	{ OPT_WITH_ARG(NULL, 'b', test_arg, "b"), "Description of b" },
+	{ OPT_WITH_ARG(NULL, 'b', test_arg, show_arg, "b"), "Description of b" },
 	OPT_ENDTABLE
 };
 
 struct opt_table long_table[] = {
 	/* Long opts, different args. */
 	{ OPT_WITHOUT_ARG("ddd", 0, test_noarg, "ddd"), "Description of ddd" },
-	{ OPT_WITH_ARG("eee", 0, test_arg, "eee"), "Description of eee" },
+	{ OPT_WITH_ARG("eee", 0, test_arg, show_arg, "eee"), },
 	OPT_ENDTABLE
 };
 
@@ -81,14 +86,15 @@ struct opt_table long_and_short_table[] = {
 	/* Short and long, different args. */
 	{ OPT_WITHOUT_ARG("ggg", 'g', test_noarg, "ggg"),
 	  "Description of ggg" },
-	{ OPT_WITH_ARG("hhh", 'h', test_arg, "hhh"), "Description of hhh"},
+	{ OPT_WITH_ARG("hhh", 'h', test_arg, NULL, "hhh"),
+	  "Description of hhh"},
 	OPT_ENDTABLE
 };
 
 /* Sub-table test. */
 struct opt_table subtables[] = {
 	/* Short and long, no description */
-	{ OPT_WITH_ARG("jjj", 'j', test_arg, "jjj") },
+	{ OPT_WITH_ARG("jjj", 'j', test_arg, show_arg, "jjj") },
 	OPT_SUBTABLE(short_table, NULL),
 	OPT_SUBTABLE(long_table, "long table options"),
 	OPT_SUBTABLE(long_and_short_table, opt_table_hidden),

ccan/opt/test/utils.h

@@ -8,7 +8,8 @@ extern char *err_output;
 
 extern unsigned int test_cb_called;
 char *test_noarg(void *arg);
-char *test_arg(const char *optarg, void *arg);
+char *test_arg(const char *optarg, const char *arg);
+void show_arg(char buf[OPT_SHOW_LEN], const char *arg);
 
 extern struct opt_table short_table[];
 extern struct opt_table long_table[];

ccan/opt/usage.c

@@ -25,6 +25,8 @@ static unsigned write_short_options(char *str)
 	return num;
 }
 
+#define OPT_SPACE_PAD "                    "
+
 /* FIXME: Get all purdy. */
 char *opt_usage(const char *argv0, const char *extra)
 {
@@ -45,8 +47,14 @@ char *opt_usage(const char *argv0, const char *extra)
 			len += strlen("--%s/-%c") + strlen(" <arg>");
 			if (opt_table[i].longopt)
 				len += strlen(opt_table[i].longopt);
-			if (opt_table[i].desc)
-				len += 20 + strlen(opt_table[i].desc);
+			if (opt_table[i].desc) {
+				len += strlen(OPT_SPACE_PAD)
+					+ strlen(opt_table[i].desc) + 1;
+			}
+			if (opt_table[i].show) {
+				len += strlen("(default: %s)")
+					+ OPT_SHOW_LEN + sizeof("...");
+			}
 			len += strlen("\n");
 		}
 	}
@@ -89,11 +97,20 @@ char *opt_usage(const char *argv0, const char *extra)
 			len = sprintf(p, "--%s", opt_table[i].longopt);
 		if (opt_table[i].flags == OPT_HASARG)
 			len += sprintf(p + len, " <arg>");
-		if (opt_table[i].desc) {
+		if (opt_table[i].desc || opt_table[i].show)
 			len += sprintf(p + len, "%.*s",
-				       len < 20 ? 20 - len : 1,
-				       "                    ");
+				       len < strlen(OPT_SPACE_PAD)
+				       ? strlen(OPT_SPACE_PAD) - len : 1,
+				       OPT_SPACE_PAD);
+
+		if (opt_table[i].desc)
 			len += sprintf(p + len, "%s", opt_table[i].desc);
+		if (opt_table[i].show) {
+			char buf[OPT_SHOW_LEN + sizeof("...")];
+			strcpy(buf + OPT_SHOW_LEN, "...");
+			opt_table[i].show(buf, opt_table[i].arg);
+			len += sprintf(p + len, "%s(default: %s)",
+				       opt_table[i].desc ? " " : "", buf);
 		}
 		p += len;
 		p += sprintf(p, "\n");