Failure of config file parsing is a hard failure

compton will now quit if it fails to parse the config file.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/err.h

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright (c) 2019 Yuxuan Shui <yshuiv7@gmail.com>
+
+#pragma once
+#include <stdbool.h>
+#include <stdint.h>
+#include "compiler.h"
+
+// Functions for error reporting, adopted from Linux
+
+// INFO in user space we can probably be more liberal about what pointer we consider
+// error. e.g. In x86_64 Linux, all addresses with the highest bit set is invalid in user
+// space.
+#define MAX_ERRNO 4095
+
+static inline void *must_use ERR_PTR(intptr_t err) {
+	return (void *)err;
+}
+
+static inline intptr_t must_use PTR_ERR(void *ptr) {
+	return (intptr_t)ptr;
+}
+
+static inline bool must_use IS_ERR(void *ptr) {
+	return unlikely((uintptr_t)ptr > (uintptr_t)-MAX_ERRNO);
+}
+
+static inline bool must_use IS_ERR_OR_NULL(void *ptr) {
+	return unlikely(!ptr) || IS_ERR(ptr);
+}
+
+static inline intptr_t must_use PTR_ERR_OR_ZERO(void *ptr) {
+	if (IS_ERR(ptr)) {
+		return PTR_ERR(ptr);
+	}
+	return 0;
+}