LibC: Add barebones <complex.h>

Author: https://github.com/petelliott
Commit: 3f0be4e9ea
Pull-request: https://github.com/SerenityOS/serenity/pull/14059
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/BertalanD
Reviewed-by: https://github.com/EWouters
Reviewed-by: https://github.com/gmta

Userland/Libraries/LibC/complex.cpp

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2022, Peter Elliott <pelliott@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <complex.h>
+
+extern "C" {
+
+// Function definitions of this form "type (name)(args)" are intentional, to
+// prevent macro versions of "name" from being incorrectly expanded. These
+// functions are here to provide external linkage to their macro implementations.
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/creal.html
+float(crealf)(float complex z)
+{
+    return crealf(z);
+}
+
+double(creal)(double complex z)
+{
+    return creal(z);
+}
+
+long double(creall)(long double complex z)
+{
+    return creall(z);
+}
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/cimag.html
+double(cimag)(double complex z)
+{
+    return cimag(z);
+}
+
+float(cimagf)(float complex z)
+{
+    return cimagf(z);
+}
+
+long double(cimagl)(long double complex z)
+{
+    return cimagl(z);
+}
+}