4 files changed, 115 insertions, 0 deletions
diff --git a/nihil.core/CMakeLists.txt b/nihil.core/CMakeLists.txt
new file mode 100644
index 0000000..4564640
--- /dev/null
+++ b/nihil.core/CMakeLists.txt
@@ -0,0 +1,11 @@
+# This source code is released into the public domain.
+
+add_library(nihil.core STATIC)
+target_sources(nihil.core
+	PUBLIC FILE_SET modules TYPE CXX_MODULES FILES
+	nihil.core.ccm
+	errc.ccm
+
+	PRIVATE
+	errc.cc
+)
diff --git a/nihil.core/errc.cc b/nihil.core/errc.cc
new file mode 100644
index 0000000..35c9d8f
--- /dev/null
+++ b/nihil.core/errc.cc
@@ -0,0 +1,51 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <string>
+#include <system_error>
+
+module nihil.core;
+
+namespace nihil {
+
+struct nihil_error_category final : std::error_category {
+	[[nodiscard]] auto name() const noexcept -> char const * override;
+	[[nodiscard]] auto message(int err) const -> std::string override;
+};
+
+[[nodiscard]] auto nihil_category() noexcept -> std::error_category &
+{
+	static auto category = nihil_error_category();
+	return category;
+}
+
+auto make_error_condition(errc ec) -> std::error_condition
+{
+	return {static_cast<int>(ec), nihil_category()};
+}
+
+auto nihil_error_category::name() const noexcept -> char const *
+{
+	return "nihil";
+}
+
+auto nihil_error_category::message(int err) const -> std::string
+{
+	switch (static_cast<errc>(err)) {
+	case errc::no_error:
+		return "No error";
+	case errc::incomplete_command:
+		return "Incomplete command";
+	case errc::empty_string:
+		return "Empty string is not permitted";
+	case errc::invalid_unit:
+		return "Invalid unit specifier";
+	default:
+		return "Undefined error";
+	}
+}
+
+} // namespace nihil
diff --git a/nihil.core/errc.ccm b/nihil.core/errc.ccm
new file mode 100644
index 0000000..c597faf
--- /dev/null
+++ b/nihil.core/errc.ccm
@@ -0,0 +1,44 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <string>
+#include <system_error>
+
+export module nihil.core:errc;
+
+namespace nihil {
+
+export enum struct errc {
+	no_error = 0,
+
+	/*
+	 * nihil.command
+	 */
+
+	incomplete_command,
+
+	/*
+	 * nihil.util
+	 */
+
+	// Empty string is not allowed.
+	empty_string,
+
+	// Invalid unit, e.g. in parse_size()
+	invalid_unit,
+};
+
+export [[nodiscard]] auto nihil_category() noexcept -> std::error_category &;
+export [[nodiscard]] auto make_error_condition(errc ec) -> std::error_condition;
+
+} // namespace nihil
+
+namespace std {
+
+export template<>
+struct is_error_condition_enum<nihil::errc> : true_type {};
+
+} // namespace std
diff --git a/nihil.core/nihil.core.ccm b/nihil.core/nihil.core.ccm
new file mode 100644
index 0000000..a7a4100
--- /dev/null
+++ b/nihil.core/nihil.core.ccm
@@ -0,0 +1,9 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+export module nihil.core;
+
+export import :errc;