Autoconf, CMake: Get the size of a void * and a time_t

With this change we know:
whether this is a 32-bit or 64-bit build ;
whether the time_t size is 32-bit or 64-bit.

At least with CMake, the SIZEOF values could be 0, if somebody's
doing a fat build on macOS and that includes both 32-bit and 64-bit
instruction sets.

Author: fxlb

CMakeLists.txt

@@ -124,6 +124,12 @@ set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/Modules)
 #
 project(tcpdump C)
 
+#
+# Export the size of void * as SIZEOF_VOID_P so that it can be
+# tested with #if.
+#
+set(SIZEOF_VOID_P "${CMAKE_SIZEOF_VOID_P}")
+
 #
 # For checking if a compiler flag works and adding it if it does.
 #
@@ -328,6 +334,14 @@ include(CheckStructHasMember)
 include(CheckVariableExists)
 include(CheckTypeSize)
 
+#
+# Get the size of a time_t, to know whether it's 32-bit or 64-bit.
+#
+cmake_push_check_state()
+set(CMAKE_EXTRA_INCLUDE_FILES time.h)
+check_type_size("time_t" SIZEOF_TIME_T)
+cmake_pop_check_state()
+
 #
 # Header files.
 #

cmakeconfig.h.in

@@ -237,6 +237,12 @@
 /* Define to the version of this package. */
 #cmakedefine PACKAGE_VERSION "@PACKAGE_VERSION@"
 
+/* The size of `time_t', as computed by sizeof. */
+#cmakedefine SIZEOF_TIME_T @SIZEOF_TIME_T@
+
+/* The size of `void *', as computed by sizeof. */
+#cmakedefine SIZEOF_VOID_P @SIZEOF_VOID_P@
+
 /* Define to 1 if you have the ANSI C header files. */
 #cmakedefine STDC_HEADERS 1
 

configure.ac

@@ -32,6 +32,15 @@ AC_LBL_C_INIT(V_CCOPT, V_INCLS)
 AC_C_INLINE
 
 AC_CHECK_HEADERS(fcntl.h rpc/rpc.h rpc/rpcent.h net/if.h)
+#
+# Get the size of a void *, to know whether this is a 32-bit or 64-bit build.
+#
+AC_CHECK_SIZEOF([void *])
+
+#
+# Get the size of a time_t, to know whether it's 32-bit or 64-bit.
+#
+AC_CHECK_SIZEOF([time_t],,[#include <time.h>])
 
 case "$host_os" in