CMake: Add custom FindIconv

Workaround for https://gitlab.kitware.com/cmake/cmake/-/issues/24695

1 files changed, 101 insertions, 0 deletions

diff --git a/CMake/FindIconv.cmake b/CMake/FindIconv.cmake
new file mode 100644
index 0000000000..d0b86fc7cb
--- /dev/null
+++ b/CMake/FindIconv.cmake
@@ -0,0 +1,101 @@
+# Based on CMake's FindIconv.cmake
+# Modified to prefer non-built-in iconv over the built-in one
+# See https://gitlab.kitware.com/cmake/cmake/-/issues/24695 for details
+# This file can be deleted once that issue has been closed and the fix has
+# made it into a satisfactory number of cmake versions.  FreeBSD is the only
+# system known to hit this so far, so "satisfactory" can probably be defined
+# as "enough that most FreeBSD users have a fixed cmake".
+
+find_path(Iconv_INCLUDE_DIR
+  NAMES "iconv.h"
+  DOC "iconv include directory")
+mark_as_advanced(Iconv_INCLUDE_DIR)
+
+find_library(Iconv_LIBRARY
+  NAMES iconv libiconv
+  NAMES_PER_DIR
+  DOC "iconv library (if not in the C library)")
+mark_as_advanced(Iconv_LIBRARY)
+
+# iconv can only be provided in libc on a POSIX system.
+if(UNIX AND (NOT Iconv_INCLUDE_DIR OR NOT Iconv_LIBRARY))
+  include(CMakePushCheckState)
+  include(CheckCXXSourceCompiles)
+  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);
+    }
+    "
+  )
+  check_cxx_source_compiles("${Iconv_IMPLICIT_TEST_CODE}" Iconv_IS_BUILT_IN)
+  cmake_pop_check_state()
+  if(Iconv_IS_BUILT_IN)
+    unset(Iconv_INCLUDE_DIR)
+    unset(Iconv_LIBRARY)
+  endif()
+else()
+  set(Iconv_IS_BUILT_IN FALSE)
+endif()
+
+set(_Iconv_REQUIRED_VARS)
+if(Iconv_IS_BUILT_IN)
+  set(_Iconv_REQUIRED_VARS _Iconv_IS_BUILT_IN_MSG)
+  set(_Iconv_IS_BUILT_IN_MSG "built in to C library")
+else()
+  set(_Iconv_REQUIRED_VARS Iconv_LIBRARY Iconv_INCLUDE_DIR)
+endif()
+
+# NOTE: glibc's iconv.h does not define _LIBICONV_VERSION
+if(Iconv_INCLUDE_DIR AND EXISTS "${Iconv_INCLUDE_DIR}/iconv.h")
+  file(STRINGS ${Iconv_INCLUDE_DIR}/iconv.h Iconv_VERSION_DEFINE REGEX "_LIBICONV_VERSION (.*)")
+
+  if(Iconv_VERSION_DEFINE MATCHES "(0x[A-Fa-f0-9]+)")
+    set(Iconv_VERSION_NUMBER "${CMAKE_MATCH_1}")
+    # encoding -> version number: (major<<8) + minor
+    math(EXPR Iconv_VERSION_MAJOR "${Iconv_VERSION_NUMBER} >> 8" OUTPUT_FORMAT HEXADECIMAL)
+    math(EXPR Iconv_VERSION_MINOR "${Iconv_VERSION_NUMBER} - (${Iconv_VERSION_MAJOR} << 8)" OUTPUT_FORMAT HEXADECIMAL)
+
+    math(EXPR Iconv_VERSION_MAJOR "${Iconv_VERSION_MAJOR}" OUTPUT_FORMAT DECIMAL)
+    math(EXPR Iconv_VERSION_MINOR "${Iconv_VERSION_MINOR}" OUTPUT_FORMAT DECIMAL)
+    set(Iconv_VERSION "${Iconv_VERSION_MAJOR}.${Iconv_VERSION_MINOR}")
+  endif()
+
+  unset(Iconv_VERSION_DEFINE)
+  unset(Iconv_VERSION_NUMBER)
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(Iconv
+  REQUIRED_VARS ${_Iconv_REQUIRED_VARS}
+  VERSION_VAR Iconv_VERSION)
+
+if(Iconv_FOUND)
+  if(Iconv_IS_BUILT_IN)
+    set(Iconv_INCLUDE_DIRS "")
+    set(Iconv_LIBRARIES "")
+  else()
+    set(Iconv_INCLUDE_DIRS "${Iconv_INCLUDE_DIR}")
+    set(Iconv_LIBRARIES "${Iconv_LIBRARY}")
+  endif()
+  if(NOT TARGET Iconv::Iconv)
+    add_library(Iconv::Iconv INTERFACE IMPORTED)
+    set_property(TARGET Iconv::Iconv PROPERTY INTERFACE_INCLUDE_DIRECTORIES "${Iconv_INCLUDE_DIRS}")
+    set_property(TARGET Iconv::Iconv PROPERTY INTERFACE_LINK_LIBRARIES "${Iconv_LIBRARIES}")
+  endif()
+endif()