checker: disallow struct int to ptr outside unsafe (#17923)

vlib/net/address.v

@@ -194,7 +194,7 @@ pub fn resolve_ipaddrs(addr string, family AddrFamily, typ SocketType) ![]Addr {
 	hints.ai_socktype = int(typ)
 	hints.ai_flags = C.AI_PASSIVE
 
-	results := &C.addrinfo(0)
+	results := &C.addrinfo(unsafe { nil })
 
 	sport := '${port}'
 

vlib/net/common.v

@@ -70,7 +70,7 @@ fn @select(handle int, test Select, timeout time.Duration) !bool {
 	// infinite timeout is signaled by passing null as the timeout to
 	// select
 	if timeout == net.infinite_timeout {
-		timeval_timeout = &C.timeval(0)
+		timeval_timeout = &C.timeval(unsafe { nil })
 	}
 
 	match test {

vlib/net/mbedtls/ssl_connection.v

@@ -379,7 +379,7 @@ fn @select(handle int, test Select, timeout time.Duration) !bool {
 	// infinite timeout is signaled by passing null as the timeout to
 	// select
 	if timeout == net.infinite_timeout {
-		timeval_timeout = &C.timeval(0)
+		timeval_timeout = &C.timeval(unsafe { nil })
 	}
 
 	match test {

vlib/net/openssl/openssl_compiles_test.v

@@ -5,7 +5,7 @@ struct Abc {
 }
 
 fn test_printing_struct_with_reference_field_of_type_ssl_ctx() {
-	a := Abc{&C.SSL_CTX(123)}
+	a := unsafe { Abc{&C.SSL_CTX(123)} }
 	dump(a)
 	sa := a.str()
 	assert sa.contains('&C.SSL_CTX(0x7b)')

vlib/net/openssl/ssl_connection.v

@@ -436,7 +436,7 @@ fn @select(handle int, test Select, timeout time.Duration) !bool {
 	// infinite timeout is signaled by passing null as the timeout to
 	// select
 	if timeout == net.infinite_timeout {
-		timeval_timeout = &C.timeval(0)
+		timeval_timeout = &C.timeval(unsafe { nil })
 	}
 
 	match test {

vlib/net/unix/common.v

@@ -42,7 +42,7 @@ fn @select(handle int, test Select, timeout time.Duration) !bool {
 	// infinite timeout is signaled by passing null as the timeout to
 	// select
 	if timeout == unix.infinite_timeout {
-		timeval_timeout = &C.timeval(0)
+		timeval_timeout = &C.timeval(unsafe { nil })
 	}
 
 	match test {