Add: introduce CMake for project management

CMake works on all our supported platforms, like MSVC, Mingw, GCC,
Clang, and many more. It allows for a single way of doing things,
so no longer we need shell scripts and vbs scripts to work on all
our supported platforms.

Additionally, CMake allows to generate project files for like MSVC,
KDevelop, etc.

This heavily reduces the lines of code we need to support multiple
platforms from a project perspective.

Addtiionally, this heavily improves our detection of libraries, etc.

1 files changed, 133 insertions, 0 deletions

diff --git a/cmake/FindIconv.cmake b/cmake/FindIconv.cmake
new file mode 100644
index 000000000..5185601ab
--- /dev/null
+++ b/cmake/FindIconv.cmake
@@ -0,0 +1,133 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+FindIconv
+---------
+
+This module finds the ``iconv()`` POSIX.1 functions on the system.
+These functions might be provided in the regular C library or externally
+in the form of an additional library.
+
+The following variables are provided to indicate iconv support:
+
+.. variable:: Iconv_FOUND
+
+  Variable indicating if the iconv support was found.
+
+.. variable:: Iconv_INCLUDE_DIRS
+
+  The directories containing the iconv headers.
+
+.. variable:: Iconv_LIBRARIES
+
+  The iconv libraries to be linked.
+
+.. variable:: Iconv_IS_BUILT_IN
+
+  A variable indicating whether iconv support is stemming from the
+  C library or not. Even if the C library provides `iconv()`, the presence of
+  an external `libiconv` implementation might lead to this being false.
+
+Additionally, the following :prop_tgt:`IMPORTED` target is being provided:
+
+.. variable:: Iconv::Iconv
+
+  Imported target for using iconv.
+
+The following cache variables may also be set:
+
+.. variable:: Iconv_INCLUDE_DIR
+
+  The directory containing the iconv headers.
+
+.. variable:: Iconv_LIBRARY
+
+  The iconv library (if not implicitly given in the C library).
+
+.. note::
+  On POSIX platforms, iconv might be part of the C library and the cache
+  variables ``Iconv_INCLUDE_DIR`` and ``Iconv_LIBRARY`` might be empty.
+
+#]=======================================================================]
+
+include(CMakePushCheckState)
+if(CMAKE_C_COMPILER_LOADED)
+  include(CheckCSourceCompiles)
+elseif(CMAKE_CXX_COMPILER_LOADED)
+  include(CheckCXXSourceCompiles)
+else()
+  # If neither C nor CXX are loaded, implicit iconv makes no sense.
+  set(Iconv_IS_BUILT_IN FALSE)
+endif()
+
+# iconv can only be provided in libc on a POSIX system.
+# If any cache variable is already set, we'll skip this test.
+if(NOT DEFINED Iconv_IS_BUILT_IN)
+  if(UNIX AND NOT DEFINED Iconv_INCLUDE_DIR AND NOT DEFINED Iconv_LIBRARY)
+    cmake_push_check_state(RESET)
+    # We always suppress the message here: Otherwise on supported systems
+    # not having iconv in their C library (e.g. those using libiconv)
+    # would always display a confusing "Looking for iconv - not found" message
+    set(CMAKE_FIND_QUIETLY TRUE)
+    # The following code will not work, but it's sufficient to see if it compiles.
+    # Note: libiconv will define the iconv functions as macros, so CheckSymbolExists
+    # will not yield correct results.
+    set(Iconv_IMPLICIT_TEST_CODE
+      "
+      #include <stddef.h>
+      #include <iconv.h>
+      int main() {
+        char *a, *b;
+        size_t i, j;
+        iconv_t ic;
+        ic = iconv_open(\"to\", \"from\");
+        iconv(ic, &a, &i, &b, &j);
+        iconv_close(ic);
+      }
+      "
+    )
+    if(CMAKE_C_COMPILER_LOADED)
+      check_c_source_compiles("${Iconv_IMPLICIT_TEST_CODE}" Iconv_IS_BUILT_IN)
+    else()
+      check_cxx_source_compiles("${Iconv_IMPLICIT_TEST_CODE}" Iconv_IS_BUILT_IN)
+    endif()
+    cmake_pop_check_state()
+  else()
+    set(Iconv_IS_BUILT_IN FALSE)
+  endif()
+endif()
+
+if(NOT Iconv_IS_BUILT_IN)
+  find_path(Iconv_INCLUDE_DIR
+    NAMES "iconv.h"
+    DOC "iconv include directory")
+  set(Iconv_LIBRARY_NAMES "iconv" "libiconv")
+else()
+  set(Iconv_INCLUDE_DIR "" CACHE FILEPATH "iconv include directory")
+  set(Iconv_LIBRARY_NAMES "c")
+endif()
+
+find_library(Iconv_LIBRARY
+  NAMES ${Iconv_LIBRARY_NAMES}
+  DOC "iconv library (potentially the C library)")
+
+mark_as_advanced(Iconv_INCLUDE_DIR)
+mark_as_advanced(Iconv_LIBRARY)
+
+include(FindPackageHandleStandardArgs)
+if(NOT Iconv_IS_BUILT_IN)
+  find_package_handle_standard_args(Iconv REQUIRED_VARS Iconv_LIBRARY Iconv_INCLUDE_DIR)
+else()
+  find_package_handle_standard_args(Iconv REQUIRED_VARS Iconv_LIBRARY)
+endif()
+
+if(Iconv_FOUND)
+  set(Iconv_INCLUDE_DIRS "${Iconv_INCLUDE_DIR}")
+  set(Iconv_LIBRARIES "${Iconv_LIBRARY}")
+  if(NOT TARGET Iconv::Iconv)
+    add_library(Iconv::Iconv INTERFACE IMPORTED)
+  endif()
+  set_property(TARGET Iconv::Iconv PROPERTY INTERFACE_INCLUDE_DIRECTORIES "${Iconv_INCLUDE_DIRS}")
+  set_property(TARGET Iconv::Iconv PROPERTY INTERFACE_LINK_LIBRARIES "${Iconv_LIBRARIES}")
+endif()