diff --git a/.clang-tidy b/.clang-tidy
index 4dbed2fe1..d38778f93 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -12,7 +12,9 @@ Checks: |
   cert-*
   concurrency-*
   cppcoreguidelines-*
+  -cppcoreguidelines-avoid-do-while
   -cppcoreguidelines-avoid-magic-numbers
+  -cppcoreguidelines-avoid-non-const-global-variables
   -cppcoreguidelines-macro-usage
   -cppcoreguidelines-misleading-capture-default-by-value
   -cppcoreguidelines-pro-bounds-constant-array-index
diff --git a/cmake/iwyu.imp b/cmake/iwyu.imp
index 208d91d30..1a19f2751 100644
--- a/cmake/iwyu.imp
+++ b/cmake/iwyu.imp
@@ -28,5 +28,8 @@
   { include: [ "@<__utility/.*>",        private, "<utility>",     public ] },
   { include: [ "@<__config>",            private, "<version>",     public ] },
 
+  # POSIX headers.
+  { include: [ "@<sys/signal.h>",        private, "<csignal>",     public ] },
+
   # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
 ]
diff --git a/source/tit/core/CMakeLists.txt b/source/tit/core/CMakeLists.txt
index c5acb0eff..3d421c723 100644
--- a/source/tit/core/CMakeLists.txt
+++ b/source/tit/core/CMakeLists.txt
@@ -16,7 +16,10 @@ set(
   "meta.hpp"
   "misc.hpp"
   "multivector.hpp"
+  "posix.cpp"
+  "posix.hpp"
   "simd.hpp"
+  "string_utils.hpp"
   "types.hpp"
   "vec_avx.hpp"
   "vec_neon.hpp"
@@ -26,11 +29,11 @@ set(
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
 
 # Create the library.
-add_library(tit_core INTERFACE ${CXX_SOURCES})
+add_library(tit_core STATIC ${CXX_SOURCES})
 add_library(tit::core ALIAS tit_core)
 
 # Link with the dependent libraries.
-target_link_libraries(tit_core INTERFACE tit::base)
+target_link_libraries(tit_core PUBLIC tit::base)
 
 # Enable static analysis.
 check_includes(tit::core)
diff --git a/source/tit/core/config.hpp b/source/tit/core/config.hpp
index d11d60b47..9c40d35ab 100644
--- a/source/tit/core/config.hpp
+++ b/source/tit/core/config.hpp
@@ -28,6 +28,12 @@
 #define TIT_LIBCPP 0
 #endif
 
+#ifdef _WIN32
+#define TIT_HAVE_SIGACTION 0
+#else
+#define TIT_HAVE_SIGACTION 1
+#endif
+
 /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
 
 #ifndef TIT_ENABLE_TBB
diff --git a/source/tit/core/posix.cpp b/source/tit/core/posix.cpp
new file mode 100644
index 000000000..fcb00fe75
--- /dev/null
+++ b/source/tit/core/posix.cpp
@@ -0,0 +1,94 @@
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *\
+ * Part of the Tit Solver project, under the MIT License
+ * See /LICENSE.md for license information.
+ * SPDX-License-Identifier: MIT
+\* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+#include <algorithm>
+#include <csignal>
+#include <functional>
+#include <tuple>
+#include <vector>
+
+#include "tit/core/assert.hpp"
+#include "tit/core/config.hpp"
+#include "tit/core/posix.hpp"
+
+namespace tit::posix {
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+std::vector<const SignalHandler*> SignalHandler::handlers_{};
+
+#if !TIT_IWYU
+SignalHandler::SignalHandler()
+    : SignalHandler({SIGINT, SIGTERM, SIGABRT, SIGSEGV, SIGILL, SIGFPE}) {}
+#endif
+
+SignalHandler::SignalHandler(std::initializer_list<int> signal_numbers) {
+  // Register the current handler object.
+  handlers_.push_back(this);
+  // Register the new signal actions (or handlers).
+#if TIT_HAVE_SIGACTION
+  prev_actions_.reserve(signal_numbers.size());
+  for (const auto signal_number : signal_numbers) {
+    // Prepare the new action.
+    sigaction_t signal_action{};
+    signal_action.sa_flags = 0;
+    signal_action.sa_handler = &handle_signal_;
+    sigemptyset(&signal_action.sa_mask);
+    // Register the new action and store the previous one.
+    sigaction_t prev_signal_action{};
+    const auto status =
+        sigaction(signal_number, &signal_action, &prev_signal_action);
+    TIT_ENSURE(status == 0, "Unable to set the signal action!");
+    prev_actions_.emplace_back(signal_number, prev_signal_action);
+  }
+#else
+  prev_handlers_.reserve(signal_numbers.size());
+  for (const auto signal_number : signal_numbers) {
+    // Register the new handler and store the previous one.
+    const auto prev_signal_handler = signal(signal_number, &handle_signal_);
+    TIT_ENSURE(prev_signal_handler != SIG_ERR,
+               "Unable to set the signal handler!");
+    prev_handlers_.emplace_back(signal_number, prev_signal_handler);
+  }
+#endif
+}
+
+SignalHandler::~SignalHandler() noexcept {
+  // Restore the old signal handlers or actions.
+#if TIT_HAVE_SIGACTION
+  for (auto& [signal_number, prev_signal_action] : prev_actions_) {
+    const auto status = sigaction(signal_number, &prev_signal_action, nullptr);
+    TIT_ENSURE(status == 0, "Unable to reset the signal action!");
+  }
+#else
+  for (const auto& [signal_number, prev_signal_handler] : prev_handlers_) {
+    const auto signal_handler = signal(signal_number, prev_signal_handler);
+    TIT_ENSURE(signal_handler != SIG_ERR,
+               "Unable to reset the signal handler!");
+  }
+#endif
+  // Unregister the current signal handler.
+  TIT_ASSERT(handlers_.back() == this, "Signal handler was not registered!");
+  handlers_.pop_back();
+}
+
+void SignalHandler::handle_signal_(int signal_number) noexcept {
+  // Traverse the registered handler and find the one that handles the signal
+  // that we've intercepted.
+  for (const auto* handler : handlers_ | std::views::reverse) {
+    TIT_ASSERT(handler != nullptr, "Invalid handler was registered.");
+    const auto iter = std::ranges::find(handler->signals(), signal_number);
+    if (iter != handler->signals().end()) {
+      handler->on_signal(signal_number);
+      return;
+    }
+  }
+  TIT_ASSERT(false, "Interpected a signal that has no handler!");
+}
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+} // namespace tit::posix
diff --git a/source/tit/core/posix.hpp b/source/tit/core/posix.hpp
new file mode 100644
index 000000000..abe0d02a2
--- /dev/null
+++ b/source/tit/core/posix.hpp
@@ -0,0 +1,80 @@
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *\
+ * Part of the Tit Solver project, under the MIT License
+ * See /LICENSE.md for license information.
+ * SPDX-License-Identifier: MIT
+\* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+#pragma once
+
+#include <csignal> // IWYU pragma: keep
+#include <initializer_list>
+#include <ranges>
+#include <tuple>
+#include <vector>
+
+#include "tit/core/config.hpp"
+
+namespace tit::posix {
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+/******************************************************************************\
+ ** POSIX signal handler.
+\******************************************************************************/
+class SignalHandler {
+public:
+
+  /** Initialize signal handling for the common signals. */
+  SignalHandler()
+#if TIT_IWYU
+      = default
+#endif
+      ;
+  /** Initialize signal handling for the specified signals. */
+  SignalHandler(std::initializer_list<int> signal_numbers);
+
+  /** Signal handler is not move-constructible. */
+  SignalHandler(SignalHandler&&) = delete;
+  /** Signal handler is not movable. */
+  auto operator=(SignalHandler&&) -> SignalHandler& = delete;
+
+  /** Signal handler is not copy-constructible. */
+  SignalHandler(const SignalHandler&) = delete;
+  /** Signal handler is not copyable. */
+  auto operator=(const SignalHandler&) -> SignalHandler& = delete;
+
+  /** Reset signal handling. */
+  virtual ~SignalHandler() noexcept;
+
+  /** A range of handled signals. */
+  auto signals() const noexcept {
+#if TIT_HAVE_SIGACTION
+    return prev_actions_ | std::views::keys;
+#else
+    return prev_handlers_ | std::views::keys;
+#endif
+  }
+
+protected:
+
+  /** Signal interception callback. */
+  virtual void on_signal(int signal_number) const = 0;
+
+private:
+
+#if TIT_HAVE_SIGACTION
+  using sigaction_t = struct sigaction;
+  std::vector<std::tuple<int, sigaction_t>> prev_actions_;
+#else
+  using sighandler_t = void (*)(int);
+  std::vector<std::tuple<int, sighandler_t>> prev_handlers_;
+#endif
+
+  static std::vector<const SignalHandler*> handlers_;
+  static void handle_signal_(int signal_number) noexcept;
+
+}; // class SignalHandler
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+} // namespace tit::posix
diff --git a/source/tit/core/string_utils.hpp b/source/tit/core/string_utils.hpp
new file mode 100644
index 000000000..61a4e3657
--- /dev/null
+++ b/source/tit/core/string_utils.hpp
@@ -0,0 +1,49 @@
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *\
+ * Part of the Tit Solver project, under the MIT License
+ * See /LICENSE.md for license information.
+ * SPDX-License-Identifier: MIT
+\* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+#include <concepts>
+#include <ranges>
+#include <string>
+#include <string_view>
+
+#include "tit/core/misc.hpp"
+
+namespace tit::string_utils {
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+/** A string type: `const char*`, `std::string`, `std::string_view`, etc. */
+template<class String>
+concept string = std::constructible_from<std::string_view, String>;
+
+/** A range of strings. */
+template<class Strings>
+concept string_range =
+    std::ranges::range<Strings> && string<std::ranges::range_value_t<Strings>>;
+
+/** An input range of strings. */
+template<class Strings>
+concept input_string_range =
+    string_range<Strings> && std::ranges::input_range<Strings>;
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+/** Join the string with delimiter. */
+template<input_string_range Strings>
+constexpr auto join(std::string_view with, Strings&& strings) -> std::string {
+  TIT_ASSUME_UNIVERSAL(Strings, strings);
+  if (std::ranges::empty(strings)) return "";
+  std::string result(*strings.begin());
+  for (const auto& string : strings | std::views::drop(1)) {
+    result += with;
+    result += string;
+  }
+  return result;
+}
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+} // namespace tit::string_utils
diff --git a/tests/core/CMakeLists.txt b/tests/core/CMakeLists.txt
index 663119d7f..2874200d7 100644
--- a/tests/core/CMakeLists.txt
+++ b/tests/core/CMakeLists.txt
@@ -9,6 +9,8 @@ set(
   CXX_SOURCES
   "math_tests.cpp"
   "mdvector_tests.cpp"
+  "posix_tests.cpp"
+  "string_utils_tests.cpp"
   "vec_tests.cpp")
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
@@ -20,7 +22,7 @@ add_executable(tit::core_tests ALIAS tit_core_tests)
 # Link with the dependent libraries.
 target_link_libraries(tit_core_tests PRIVATE tit::core)
 
-# # Enable static analysis.
-# check_includes(tit::core_tests)
+# Enable static analysis.
+check_includes(tit::core_tests)
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
diff --git a/tests/core/mdvector_tests.cpp b/tests/core/mdvector_tests.cpp
index 6bbf8046c..b1504dd7e 100644
--- a/tests/core/mdvector_tests.cpp
+++ b/tests/core/mdvector_tests.cpp
@@ -41,7 +41,7 @@ TEST_CASE("tit::core::Mdspan") {
   CHECK(mdspan[1][0] == 4);
   CHECK(mdspan[2][1] == 8);
   // Check data access using iterators.
-  const auto iter = std::ranges::find(mdspan, 7);
+  const auto* iter = std::ranges::find(mdspan, 7);
   CHECK(iter - mdspan.begin() == 6);
 }
 
diff --git a/tests/core/posix_tests.cpp b/tests/core/posix_tests.cpp
new file mode 100644
index 000000000..a8d837e81
--- /dev/null
+++ b/tests/core/posix_tests.cpp
@@ -0,0 +1,80 @@
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *\
+ * Part of the Tit Solver project, under the MIT License
+ * See /LICENSE.md for license information.
+ * SPDX-License-Identifier: MIT
+\* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+#include <csignal>
+#include <initializer_list>
+
+#include <doctest/doctest.h>
+
+#include "tit/core/posix.hpp"
+
+namespace {
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+class MyHandler final : public tit::posix::SignalHandler {
+public:
+
+  MyHandler(int& handled_signal_number,
+            std::initializer_list<int> signal_numbers)
+      : tit::posix::SignalHandler(signal_numbers),
+        handled_signal_number_{&handled_signal_number} {}
+
+protected:
+
+  void on_signal(int signal_number) const final {
+    *handled_signal_number_ = signal_number;
+  }
+
+private:
+
+  int* handled_signal_number_;
+
+}; // class MyHandler
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+// NOLINTBEGIN(cert-err33-c)
+
+TEST_CASE("tit::core::posix::SignalHandler") {
+  int handled_1 = 0, handled_2 = 0;
+  const auto reset = [&] { handled_1 = handled_2 = 0; };
+  { // Create the first handler for two signals.
+    const MyHandler handler_1(handled_1, {SIGUSR1, SIGUSR2});
+    {
+      // Create the second handler for the two signals.
+      const MyHandler handler_2(handled_2, {SIGUSR2, SIGCHLD});
+      {
+        // Raise the signal that shall be intercepted by the first handler.
+        reset();
+        raise(SIGUSR1);
+        CHECK(handled_1 == SIGUSR1);
+        CHECK(handled_2 == 0);
+        // Raise the signal that it shall be intercepted by the second handler.
+        reset();
+        raise(SIGUSR2);
+        CHECK(handled_1 == 0);
+        CHECK(handled_2 == SIGUSR2);
+      }
+    }
+    // Raise the signal that shall be intercepted by the first handler.
+    reset();
+    raise(SIGUSR2);
+    CHECK(handled_1 == SIGUSR2);
+    CHECK(handled_2 == 0);
+    // Raise the signal that shall not be intercepted by any handlers.
+    reset();
+    raise(SIGCHLD);
+    CHECK(handled_1 == 0);
+    CHECK(handled_2 == 0);
+  }
+}
+
+// NOLINTEND(cert-err33-c)
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+} // namespace
diff --git a/tests/core/string_utils_tests.cpp b/tests/core/string_utils_tests.cpp
new file mode 100644
index 000000000..6cf70ad1d
--- /dev/null
+++ b/tests/core/string_utils_tests.cpp
@@ -0,0 +1,32 @@
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *\
+ * Part of the Tit Solver project, under the MIT License
+ * See /LICENSE.md for license information.
+ * SPDX-License-Identifier: MIT
+\* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+#include <string>
+#include <vector>
+
+#include <doctest/doctest.h>
+
+#include "tit/core/string_utils.hpp"
+
+namespace {
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+TEST_CASE("tit::core::string_utils::join") {
+  // Join a non-empty string list.
+  const std::vector<std::string> strings{
+      "budgie", "cockatiel", "cockatoo", "macao", "ringneck",
+  };
+  CHECK(tit::string_utils::join(", ", strings) ==
+        "budgie, cockatiel, cockatoo, macao, ringneck");
+  // Join an empty string list.
+  const std::vector<std::string> empty_strings{};
+  CHECK(tit::string_utils::join("...", empty_strings) == "");
+}
+
+/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+} // namespace