basic: Move assertion specific functions to assert-util.h

Various functions in log.h are only used by asserts, and there's
enough assertion related stuff in macro.h to justify a separate header
which also makes it easier to avoid circular dependencies.

Let's introduce assert-util.h and an accompanying fundamental header
and move all the assertion related stuff over there. PROJECT_FILE is
moved over to macro.h.

src/basic/assert-util.c

@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <stdio.h>
+
+#include "assert-util.h"
+#include "errno-util.h"
+#include "log.h"
+
+static bool assert_return_is_critical = BUILD_MODE_DEVELOPER;
+
+/* Akin to glibc's __abort_msg; which is private and we hence cannot
+ * use here. */
+static char *log_abort_msg = NULL;
+
+void log_set_assert_return_is_critical(bool b) {
+        assert_return_is_critical = b;
+}
+
+bool log_get_assert_return_is_critical(void) {
+        return assert_return_is_critical;
+}
+
+static void log_assert(
+        int level,
+        const char *text,
+        const char *file,
+        int line,
+        const char *func,
+        const char *format) {
+
+        static char buffer[LINE_MAX];
+
+        if (_likely_(LOG_PRI(level) > log_get_max_level()))
+                return;
+
+        DISABLE_WARNING_FORMAT_NONLITERAL;
+        (void) snprintf(buffer, sizeof buffer, format, text, file, line, func);
+        REENABLE_WARNING;
+
+        log_abort_msg = buffer;
+
+        log_dispatch_internal(level, 0, file, line, func, NULL, NULL, NULL, NULL, buffer);
+}
+
+_noreturn_ void log_assert_failed(const char *text, const char *file, int line, const char *func) {
+        log_assert(LOG_CRIT, text, file, line, func,
+                   "Assertion '%s' failed at %s:%u, function %s(). Aborting.");
+        abort();
+}
+
+_noreturn_ void log_assert_failed_unreachable(const char *file, int line, const char *func) {
+        log_assert(LOG_CRIT, "Code should not be reached", file, line, func,
+                   "%s at %s:%u, function %s(). Aborting. 💥");
+        abort();
+}
+
+void log_assert_failed_return(const char *text, const char *file, int line, const char *func) {
+
+        if (assert_return_is_critical)
+                log_assert_failed(text, file, line, func);
+
+        PROTECT_ERRNO;
+        log_assert(LOG_DEBUG, text, file, line, func,
+                   "Assertion '%s' failed at %s:%u, function %s(), ignoring.");
+}