list: improve test coverage to 100%

In particular, we test the corruption cases.

ccan/list/list.c

@@ -2,6 +2,20 @@
 #include <stdlib.h>
 #include "list.h"
 
+static void *corrupt(const char *abortstr,
+		     const struct list_node *head,
+		     const struct list_node *node,
+		     unsigned int count)
+{
+	if (abortstr) {
+		fprintf(stderr,
+			"%s: prev corrupt in node %p (%u) of %p\n",
+			abortstr, node, count, head);
+		abort();
+	}
+	return NULL;
+}
+
 struct list_node *list_check_node(const struct list_node *node,
 				  const char *abortstr)
 {
@@ -10,31 +24,18 @@ struct list_node *list_check_node(const struct list_node *node,
 
 	for (p = node, n = node->next; n != node; p = n, n = n->next) {
 		count++;
-		if (n->prev != p) {
-			if (!abortstr)
-				return NULL;
-			fprintf(stderr,
-				"%s: prev corrupt in node %p (%u) of %p\n",
-				abortstr, n, count, node);
-			abort();
-		}
+		if (n->prev != p)
+			return corrupt(abortstr, node, n, count);
 	}
+	/* Check prev on head node. */
+	if (node->prev != p)
+		return corrupt(abortstr, node, node, 0);
+
 	return (struct list_node *)node;
 }
 
 struct list_head *list_check(const struct list_head *h, const char *abortstr)
 {
-	if (h->n.next == &h->n) {
-		if (h->n.prev != &h->n) {
-			if (!abortstr)
-				return NULL;
-			fprintf(stderr, "%s: prev corrupt in empty %p\n",
-				abortstr, h);
-			abort();
-		}
-		return (struct list_head *)h;
-	}
-
 	if (!list_check_node(&h->n, abortstr))
 		return NULL;
 	return (struct list_head *)h;

ccan/list/test/run-check-corrupt.c

@@ -0,0 +1,89 @@
+#include <setjmp.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <string.h>
+#include <err.h>
+
+/* We don't actually want it to exit... */
+static jmp_buf aborted;
+#define abort() longjmp(aborted, 1)
+
+#define fprintf my_fprintf
+static char printf_buffer[1000];
+
+static int my_fprintf(FILE *stream, const char *format, ...)
+{
+	va_list ap;
+	int ret;
+	va_start(ap, format);
+	ret = vsprintf(printf_buffer, format, ap);
+	va_end(ap);
+	return ret;
+}
+
+#include <ccan/list/list.h>
+#include <ccan/tap/tap.h>
+#include <ccan/list/list.c>
+
+int main(int argc, char *argv[])
+{
+	struct list_head list;
+	struct list_node n1;
+	char expect[100];
+
+	plan_tests(9);
+	/* Empty list. */
+	list.n.next = &list.n;
+	list.n.prev = &list.n;
+	ok1(list_check(&list, NULL) == &list);
+
+	/* Bad back ptr */
+	list.n.prev = &n1;
+	/* Non-aborting version. */
+	ok1(list_check(&list, NULL) == NULL);
+
+	/* Aborting version. */
+	sprintf(expect, "test message: prev corrupt in node %p (0) of %p\n",
+		&list, &list);
+	if (setjmp(aborted) == 0) {
+		list_check(&list, "test message");
+		fail("list_check on empty with bad back ptr didn't fail!");
+	} else {
+		ok1(strcmp(printf_buffer, expect) == 0);
+	}
+
+	/* n1 in list. */
+	list.n.next = &n1;
+	list.n.prev = &n1;
+	n1.prev = &list.n;
+	n1.next = &list.n;
+	ok1(list_check(&list, NULL) == &list);
+	ok1(list_check_node(&n1, NULL) == &n1);
+
+	/* Bad back ptr */
+	n1.prev = &n1;
+	ok1(list_check(&list, NULL) == NULL);
+	ok1(list_check_node(&n1, NULL) == NULL);
+
+	/* Aborting version. */
+	sprintf(expect, "test message: prev corrupt in node %p (1) of %p\n",
+		&n1, &list);
+	if (setjmp(aborted) == 0) {
+		list_check(&list, "test message");
+		fail("list_check on n1 bad back ptr didn't fail!");
+	} else {
+		ok1(strcmp(printf_buffer, expect) == 0);
+	}
+
+	sprintf(expect, "test message: prev corrupt in node %p (0) of %p\n",
+		&n1, &n1);
+	if (setjmp(aborted) == 0) {
+		list_check_node(&n1, "test message");
+		fail("list_check_node on n1 bad back ptr didn't fail!");
+	} else {
+		ok1(strcmp(printf_buffer, expect) == 0);
+	}
+
+	return exit_status();
+}

ccan/list/test/run-list_del_from-assert.c

@@ -0,0 +1,36 @@
+#define CCAN_LIST_DEBUG 1
+#include <ccan/list/list.h>
+#include <ccan/tap/tap.h>
+#include <ccan/list/list.c>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <signal.h>
+
+int main(int argc, char *argv[])
+{
+	struct list_head list1, list2;
+	struct list_node n1, n2, n3;
+	pid_t child;
+	int status;
+
+	plan_tests(1);
+	list_head_init(&list1);
+	list_head_init(&list2);
+	list_add(&list1, &n1);
+	list_add(&list2, &n2);
+	list_add_tail(&list2, &n3);
+
+	child = fork();
+	if (child) {
+		wait(&status);
+	} else {
+		/* This should abort. */
+		list_del_from(&list1, &n3);
+		exit(0);
+	}
+
+	ok1(WIFSIGNALED(status) && WTERMSIG(status) == SIGABRT);
+	list_del_from(&list2, &n3);
+	return exit_status();
+}