Refactor alloca check

Autoconf provides dedicated AC_FUNC_ALLOCA macro. This is for now the
best effort to make it simple yet effective and have it synced with
current PHP usage of alloca().

Author: petk

cmake/cmake/ConfigureChecks.cmake

@@ -43,7 +43,6 @@ endif()
 # Check headers.
 ################################################################################
 
-check_include_files(alloca.h HAVE_ALLOCA_H)
 check_include_files(arpa/inet.h HAVE_ARPA_INET_H)
 check_include_files(sys/types.h HAVE_SYS_TYPES_H)
 
@@ -408,21 +407,17 @@ else()
 endif()
 
 ################################################################################
-# Miscellaneous checks.
+# Run all checks from cmake/checks.
 ################################################################################
 
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckAVX512.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckCopyFileRange.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckFlushIo.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckFnmatch.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckFopencookie.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckGetaddrinfo.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckGethostbynameR.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckGetifaddrs.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckInline.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckIPv6.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckReentrantFunctions.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/checks/CheckWrite.cmake)
+file(GLOB checks ${CMAKE_CURRENT_LIST_DIR}/checks/Check*.cmake)
+foreach(check IN LISTS checks)
+  include(${check})
+endforeach()
+
+################################################################################
+# Miscellaneous checks.
+################################################################################
 
 # Checking file descriptor sets.
 message(CHECK_START "Checking file descriptor sets size")
@@ -443,16 +438,6 @@ else()
   message(CHECK_PASS "using system default")
 endif()
 
-if(HAVE_ALLOCA_H)
-  # Most *.nix systems.
-  check_symbol_exists(alloca alloca.h HAVE_ALLOCA)
-elseif(CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  check_symbol_exists(alloca malloc.h HAVE_ALLOCA)
-else()
-  # BSD-based systems.
-  check_symbol_exists(alloca stdlib.h HAVE_ALLOCA)
-endif()
-
 message(CHECK_START "Checking whether the compiler supports __alignof__")
 cmake_push_check_state(RESET)
   set(CMAKE_REQUIRED_QUIET TRUE)

cmake/cmake/checks/CheckAlloca.cmake

@@ -0,0 +1,39 @@
+#[=============================================================================[
+This check determines whether the system supports alloca() and follows the
+behavior of Autoconf's AC_FUNC_ALLOCA macro, with some adjustments for obsolete
+systems:
+
+* Autoconf also checks whether <alloca.h> works on certain obsolete systems.
+* Autoconf provides variable substitution to integrate a custom alloca.c
+  implementation if alloca() is not available on the system. However, PHP
+  doesn't use this feature.
+
+Result variables:
+
+* HAVE_ALLOCA
+* HAVE_ALLOCA_H
+#]=============================================================================]
+
+include(CheckIncludeFiles)
+include(CheckSymbolExists)
+
+# On Windows, alloca is defined in malloc.h as _alloca. Cache variables are
+# overridden to speed up the check and commands used for documentation purposes.
+if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+  set(PHP_HAS_ALLOCA_H FALSE)
+  set(PHP_HAS_ALLOCA TRUE)
+  check_symbol_exists(alloca malloc.h PHP_HAS_ALLOCA)
+else()
+  check_include_files(alloca.h PHP_HAS_ALLOCA_H)
+
+  if(PHP_HAS_ALLOCA_H)
+    # Most *.nix systems (Linux, macOS, Solaris/illumos, Haiku).
+    check_symbol_exists(alloca alloca.h PHP_HAS_ALLOCA)
+  else()
+    # BSD-based systems, old Linux.
+    check_symbol_exists(alloca stdlib.h PHP_HAS_ALLOCA)
+  endif()
+endif()
+
+set(HAVE_ALLOCA ${PHP_HAS_ALLOCA})
+set(HAVE_ALLOCA_H ${PHP_HAS_ALLOCA_H})

cmake/cmake/platforms/Windows.cmake

@@ -55,8 +55,6 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
   ##############################################################################
 
   set(HAVE_ALIGNOF FALSE)
-  set(HAVE_ALLOCA TRUE)
-  set(HAVE_ALLOCA_H FALSE)
   set(HAVE_ALPHASORT FALSE)
   set(HAVE_ARPA_INET_H FALSE)
   set(HAVE_ARPA_NAMESER_H FALSE)