cmake HAVE_PTRDIFF_T examples

HDFGroup/hdf5 config/cmake/ZLIBNG/CMakeLists.txt :575 

check_c_source_compiles(
    "#include <stddef.h>
     int main() {
         ptrdiff_t *a;
         (void)a;
         return 0;
    }"
    HAVE_PTRDIFF_T
)

InsightSoftwareConsortium/ITK Modules/ThirdParty/HDF5/src/itkhdf5/config/cmake/ZLIBNG/CMakeLists.txt :490 

check_c_source_compiles(
    "#include <stddef.h>
     int main() {
         ptrdiff_t *a;
         (void)a;
         return 0;
    }"
    HAVE_PTRDIFF_T
)

InsightSoftwareConsortium/ITK Modules/ThirdParty/ZLIB/src/itkzlib-ng/CMakeLists.txt :583 

check_c_source_compiles(
    "#include <stddef.h>
     int main() {
         ptrdiff_t *a;
         (void)a;
         return 0;
    }"
    HAVE_PTRDIFF_T
)

Kitware/VTK ThirdParty/netcdf/vtknetcdf/CMakeLists.txt :268 

check_type_size("ptrdiff_t" HAVE_PTRDIFF_T)