foreach: allow a single argument to foreach_int() and foreach_ptr().

David Gibson noted that foreach requires more than one argument.
There's no particularly good reason for this, other than lack of
imagination on my part.

ccan/foreach/foreach.h

@@ -10,7 +10,7 @@
 /**
  * foreach_int - iterate over a fixed series of integers
  * @i: the int-compatible iteration variable
- * @val: one or more integer-compatible values
+ * ...: one or more integer-compatible values
  *
  * This is a convenient wrapper function for setting a variable to one or
  * more explicit values in turn.  continue and break work as expected.
@@ -21,15 +21,15 @@
  *		printf("i is %i\n", i);
  *	}
  */
-#define foreach_int(i, val, ...)					\
-	for (unsigned _foreach_i = ((i) = val, 0);			\
-	     _foreach_i < sizeof((int[]) { val, __VA_ARGS__ })/sizeof(val); \
-	     (i) = (int[]) { val, __VA_ARGS__, 0 }[++_foreach_i])
+#define foreach_int(i, ...)						\
+	for (unsigned _foreach_i = (((i) = ((int[]) { __VA_ARGS__ })[0]), 0); \
+	     _foreach_i < sizeof((int[]) { __VA_ARGS__ })/sizeof(int);	\
+	     (i) = ((int[]) { __VA_ARGS__, 0 })[++_foreach_i])
 
 /**
  * foreach_ptr - iterate over a non-NULL series of pointers
  * @i: the pointer iteration variable
- * @val: one or more compatible pointer values
+ * ...: one or more compatible pointer values
  *
  * This is a convenient wrapper function for setting a variable to one
  * or more explicit values in turn.  None of the values can be NULL;
@@ -42,28 +42,30 @@
  *		printf("p is %s\n", p);
  *	}
  */
-#define foreach_ptr(i, val, ...)					\
-	for (unsigned _foreach_i = (unsigned long)((i) = (val), 0);	\
+#define foreach_ptr(i, ...)					\
+	for (unsigned _foreach_i				\
+		     = (((i) = ((const void *[]){ __VA_ARGS__ })[0]), 0); \
 	     (i);							\
-	     (i) = ((FOREACH_TYPEOF(val)[]){(val), __VA_ARGS__, NULL})	\
-		     [++_foreach_i],					\
+	     (i) = (void *)((FOREACH_TYPEOF(i)[])			\
+		     { __VA_ARGS__, NULL})[++_foreach_i],		\
 		_foreach_no_nullval(_foreach_i, i,			\
-				    ((void *[]){ val, __VA_ARGS__})))
+				    ((const void *[]){ __VA_ARGS__})))
 #else /* !HAVE_FOR_LOOP_DECLARATION */
 /* GCC in C89 mode still has compound literals, but no for-declarations */
-#define foreach_int(i, val, ...)					\
-	for ((i) = (val), _foreach_iter_init(&(i));			\
-	     _foreach_iter(&(i)) < sizeof((int[]) { (val), __VA_ARGS__ }) \
+#define foreach_int(i, ...)						\
+	for ((i) = ((int[]){ __VA_ARGS__ })[0], _foreach_iter_init(&(i)); \
+	     _foreach_iter(&(i)) < sizeof((int[]) { __VA_ARGS__ })	\
 			   / sizeof(int);				\
-	     (i) = (int[]) { (val), __VA_ARGS__, 0 }[_foreach_iter_inc(&(i))])
+	     (i) = (int[]) { __VA_ARGS__, 0 }[_foreach_iter_inc(&(i))])
 
-#define foreach_ptr(i, val, ...)					\
-	for ((i) = (val), _foreach_iter_init(&(i));			\
+#define foreach_ptr(i, ...)						\
+	for ((i) = ((FOREACH_TYPEOF(i)[]){ __VA_ARGS__ })[0],		\
+		     _foreach_iter_init(&(i));				\
 	     (i);							\
-	     (i) = ((FOREACH_TYPEOF(val)[]){ (val), __VA_ARGS__, 0 })	\
+	     (i) = (void *)((FOREACH_TYPEOF(i)[]){ __VA_ARGS__, NULL }) \
 		     [_foreach_iter_inc(&(i))],				\
 		 _foreach_no_nullval(_foreach_iter(&(i)), i,		\
-				     ((void *[]){ val, __VA_ARGS__})))
+				     ((void *[]){ __VA_ARGS__})))
 
 void _foreach_iter_init(const void *i);
 unsigned int _foreach_iter(const void *i);
@@ -76,25 +78,23 @@ unsigned int _foreach_iter_inc(const void *i);
 	assert((i) >= sizeof(arr)/sizeof(arr[0]) || (p))
 
 #if HAVE_TYPEOF
-#define FOREACH_TYPEOF(val) __typeof__(&*(val))
+#define FOREACH_TYPEOF(i) __typeof__(i)
 #else
-#define FOREACH_TYPEOF(val) void *
+#define FOREACH_TYPEOF(i) const void *
 #endif
 
 #else /* !HAVE_COMPOUND_LITERALS */
 
 /* No compound literals, but it's still (just) possible. */
-#define foreach_int(i, val, ...)					\
-	for (i = _foreach_intval_init(&(i), val, __VA_ARGS__,	\
-					  _foreach_term);		\
-	     !_foreach_intval_done(&i);				\
-	     i = _foreach_intval_next(&(i), val, __VA_ARGS__,	\
-					  _foreach_term))
+#define foreach_int(i, ...)						\
+	for (i = _foreach_intval_init(&(i), __VA_ARGS__, _foreach_term); \
+	     !_foreach_intval_done(&i);					\
+	     i = _foreach_intval_next(&(i), __VA_ARGS__, _foreach_term))
 
-#define foreach_ptr(i, val, ...)					\
-	for (i = _foreach_ptrval_init(&(i), val, __VA_ARGS__, NULL);	\
+#define foreach_ptr(i, ...)						\
+	for (i = _foreach_ptrval_init(&(i), __VA_ARGS__, NULL);		\
 	     (i);							\
-	     i = _foreach_ptrval_next(&(i), val, __VA_ARGS__, NULL))
+	     i = _foreach_ptrval_next(&(i), __VA_ARGS__, NULL))
 
 extern int _foreach_term;
 int _foreach_intval_init(const void *i, int val, ...);

ccan/foreach/test/run-single-arg.c

@@ -0,0 +1,31 @@
+#include <ccan/foreach/foreach.h>
+#include <ccan/tap/tap.h>
+#include <stdio.h>
+#include <string.h>
+#include <ccan/foreach/foreach.c>
+
+int main(void)
+{
+	int i, num;
+	const char *p;
+
+	plan_tests(5);
+
+	num = 0;
+	foreach_int(i, 0) {
+		ok1(i == 0);
+		num++;
+	}
+	ok1(num == 1);
+
+	num = 0;
+	foreach_ptr(p, "hello") {
+		ok1(strcmp("hello", p) == 0);
+		num++;
+	}
+	ok1(p == NULL);
+	ok1(num == 1);
+
+	return exit_status();
+}
+