altstack: Don't use 0 pointer literals

In a number of places the altstack module uses a literal '0' for pointer
values.  That's correct C, but doesn't make it obvious on a quick read
whether values are integers or pointers.  This patch changes those cases
to use the NULL define instead.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

ccan/altstack/_info

@@ -63,8 +63,8 @@
  *		void *out;
  *
  *		assert(argc == 3);
- *		stk_max = strtol(argv[1], 0, 0) * 1024 * 1024;
- *		vla_sz  = strtol(argv[2], 0, 0) * 1024 * 1024;
+ *		stk_max = strtol(argv[1], NULL, 0) * 1024 * 1024;
+ *		vla_sz  = strtol(argv[2], NULL, 0) * 1024 * 1024;
  *		assert(stk_max > 0 && vla_sz > 0);
  *
  *		snprintf(maps, sizeof(maps), "egrep '\\[stack' /proc/%d/maps", getpid());

ccan/altstack/altstack.c

@@ -78,10 +78,10 @@ int altstack(rlim_t max, void *(*fn)(void *), void *arg, void **out)
 
 	state.fn  = fn;
 	state.arg = arg;
-	state.out = 0;
+	state.out = NULL;
 	state.max = max;
 	state.ebuf[state.elen = 0] = '\0';
-	if (out) *out = 0;
+	if (out) *out = NULL;
 
 	// if the first page below the mapping is in use, we get max-pgsz usable bytes
 	// add pgsz to max to guarantee at least max usable bytes
@@ -91,7 +91,7 @@ int altstack(rlim_t max, void *(*fn)(void *), void *arg, void **out)
 	ok(setrlimit(RLIMIT_STACK, &(struct rlimit) { state.max, rl_save.rlim_max }), 1);
 	undo++;
 
-	ok(m = mmap(0, max, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_GROWSDOWN|MAP_NORESERVE, -1, 0), 1);
+	ok(m = mmap(NULL, max, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_GROWSDOWN|MAP_NORESERVE, -1, 0), 1);
 	undo++;
 
 	if (setjmp(state.jmp) == 0) {
@@ -130,9 +130,9 @@ out:
 
 	switch (undo) {
 	case 4:
-		ok(sigaction(SIGSEGV, &sa_save, 0), 0);
+		ok(sigaction(SIGSEGV, &sa_save, NULL), 0);
 	case 3:
-		ok(sigaltstack(&ss_save, 0), 0);
+		ok(sigaltstack(&ss_save, NULL), 0);
 	case 2:
 		ok(munmap(m, max), 0);
 	case 1:

ccan/altstack/altstack.h

@@ -52,7 +52,7 @@
  *	static void *wrap(void *i)
  *	{
  *		dn((unsigned long) i);
- *		return 0;
+ *		return NULL;
  *	}
  *
  *	#define MiB (1024UL*1024UL)
@@ -60,9 +60,9 @@
  *	{
  *		unsigned long n;
  *		assert(argc == 2);
- *		n = strtoul(argv[1], 0, 0);
+ *		n = strtoul(argv[1], NULL, 0);
  *
- *		if (altstack(32*MiB, wrap, (void *) n, 0) != 0)
+ *		if (altstack(32*MiB, wrap, (void *) n, NULL) != 0)
  *			altstack_perror();
  *
  *		printf("%d\n", depth);

ccan/altstack/test/run.c

@@ -87,43 +87,43 @@ int main(void)
 
 	plan_tests(50);
 
-	chkfail(getrlimit_,	altstack(8*MiB, wrap, int2ptr(0), 0) == -1, e(getrlimit_),
+	chkfail(getrlimit_,	altstack(8*MiB, wrap, int2ptr(0), NULL) == -1, e(getrlimit_),
 		0,
 		0);
 
-	chkfail(setrlimit_,	altstack(8*MiB, wrap, int2ptr(0), 0) == -1, e(setrlimit_),
+	chkfail(setrlimit_,	altstack(8*MiB, wrap, int2ptr(0), NULL) == -1, e(setrlimit_),
 		getrlimit_,
 		0);
 
-	chkfail(mmap_,		altstack(8*MiB, wrap, int2ptr(0), 0) == -1, e(mmap_),
+	chkfail(mmap_,		altstack(8*MiB, wrap, int2ptr(0), NULL) == -1, e(mmap_),
 		getrlimit_|setrlimit_,
 		setrlimit_);
 
-	chkfail(sigaltstack_,	altstack(8*MiB, wrap, int2ptr(0), 0) == -1, e(sigaltstack_),
+	chkfail(sigaltstack_,	altstack(8*MiB, wrap, int2ptr(0), NULL) == -1, e(sigaltstack_),
 		getrlimit_|setrlimit_|mmap_,
 		setrlimit_|munmap_);
 
-	chkfail(sigaction_,	altstack(8*MiB, wrap, int2ptr(0), 0) == -1, e(sigaction_),
+	chkfail(sigaction_,	altstack(8*MiB, wrap, int2ptr(0), NULL) == -1, e(sigaction_),
 		getrlimit_|setrlimit_|mmap_|sigaltstack_,
 		setrlimit_|munmap_|sigaltstack_);
 
-	chkfail(munmap_,	altstack(8*MiB, wrap, int2ptr(0), 0) ==  1, e(munmap_),
+	chkfail(munmap_,	altstack(8*MiB, wrap, int2ptr(0), NULL) ==  1, e(munmap_),
 		getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_,
 		setrlimit_|sigaltstack_|sigaction_);
 	if (fail = 0, munmap(m_, msz_) == -1)
 		err(1, "munmap");
 
-	chkok(			altstack(1*MiB, wrap, int2ptr(1000000), 0) == -1, EOVERFLOW,
+	chkok(			altstack(1*MiB, wrap, int2ptr(1000000), NULL) == -1, EOVERFLOW,
 		getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_,
 		setrlimit_|munmap_|sigaltstack_|sigaction_);
 
 	// be sure segv catch is repeatable (SA_NODEFER)
-	chkok(			altstack(1*MiB, wrap, int2ptr(1000000), 0) == -1, EOVERFLOW,
+	chkok(			altstack(1*MiB, wrap, int2ptr(1000000), NULL) == -1, EOVERFLOW,
 		getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_,
 		setrlimit_|munmap_|sigaltstack_|sigaction_);
 
 	used = 1;
-	chkfail(munmap_,	altstack(1*MiB, wrap, int2ptr(1000000), 0) == -1, EOVERFLOW,
+	chkfail(munmap_,	altstack(1*MiB, wrap, int2ptr(1000000), NULL) == -1, EOVERFLOW,
 		getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_,
 		setrlimit_|sigaltstack_|sigaction_);
 	if (fail = 0, munmap(m_, msz_) == -1)
@@ -150,7 +150,7 @@ int main(void)
 	ok1(strcmp(buf, estr "\n") == 0);
 
 	used = 1;
-	chkok(			altstack(8*MiB, wrap, int2ptr(1000000), 0) == -1, EOVERFLOW,
+	chkok(			altstack(8*MiB, wrap, int2ptr(1000000), NULL) == -1, EOVERFLOW,
 		getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_,
 		setrlimit_|munmap_|sigaltstack_|sigaction_);
 
@@ -158,7 +158,7 @@ int main(void)
 	ok1(used >= 8*MiB - pgsz && used <= 8*MiB + pgsz);
 
 	used = 0;
-	chkok(			altstack(8*MiB, wrap, int2ptr(100000), 0) == 0, 0,
+	chkok(			altstack(8*MiB, wrap, int2ptr(100000), NULL) == 0, 0,
 		getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_|munmap_,
 		setrlimit_|munmap_|sigaltstack_|sigaction_);