Fix PIC and IPO settings for 32-bit machines

Author: petk

cmake/cmake/Bootstrap.cmake

@@ -16,3 +16,6 @@ endif()
 
 # Check whether to enable interprocedural optimization.
 include(PHP/InterproceduralOptimization)
+
+# Set CMAKE_POSITION_INDEPENDENT_CODE.
+include(PHP/PositionIndependentCode)

cmake/cmake/CMakeDefaults.cmake

@@ -26,9 +26,6 @@ if(
   set(CMAKE_COLOR_DIAGNOSTICS ON)
 endif()
 
-# Disable PIC for all targets. PIC is enabled for shared extensions manually.
-set(CMAKE_POSITION_INDEPENDENT_CODE OFF)
-
 # Set empty prefix for targets instead of default "lib".
 set(CMAKE_SHARED_LIBRARY_PREFIX_C "")
 set(CMAKE_SHARED_MODULE_PREFIX_C "")

cmake/cmake/modules/PHP/InterproceduralOptimization.cmake

@@ -42,6 +42,14 @@ elseif(CMAKE_C_COMPILER_ID STREQUAL "AppleClang")
     STATUS
     "Interprocedural optimization (IPO) disabled (AppleClang)"
   )
+elseif(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_SIZEOF_VOID_P EQUAL 4)
+  # On 32-bit Linux machine, this produced undefined references linker errors.
+  set(CMAKE_INTERPROCEDURAL_OPTIMIZATION OFF)
+
+  message(
+    STATUS
+    "Interprocedural optimization (IPO) disabled (Clang on 32-bit)"
+  )
 else()
   include(CheckIPOSupported)
   check_ipo_supported(RESULT result)

cmake/cmake/modules/PHP/PositionIndependentCode.cmake

@@ -0,0 +1,13 @@
+#[=============================================================================[
+Check whether to enable the POSITION_INDEPENDENT_CODE or not.
+
+https://cmake.org/cmake/help/latest/variable/CMAKE_POSITION_INDEPENDENT_CODE.html
+]=============================================================================]#
+
+if(CMAKE_COMPILER_ID STREQUAL "Clang" AND CMAKE_SIZEOF_VOID_P EQUAL 4)
+  # On 32-bit Linux and FreeBSD at least when using Clang, the pic is required.
+  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+else()
+  # Disable PIC for all targets. PIC is enabled for shared extensions manually.
+  set(CMAKE_POSITION_INDEPENDENT_CODE OFF)
+endif()