test_serialize_4b_bytestring / test_serialize_8b_bytestring tests fail on 32-bit systems (size_t overflow) #263

Describe the bug

On i686-linux targets libcbor tests fail as:

[ RUN      ] test_serialize_4b_bytestring
[  ERROR   ] --- 0 != 0x100000004
[   LINE   ] --- libcbor/test/cbor_serialize_test.c:...: error: Failure!
[  FAILED  ] test_serialize_4b_bytestring
...
[  FAILED  ] test_serialize_8b_bytestring

I think it happens in this code: https://github.com/PJK/libcbor/blob/master/test/cbor_serialize_test.c#L161-L183

Annotated:

static void test_serialize_4b_bytestring(void **_CBOR_UNUSED(_state)) {
  cbor_item_t *item = cbor_new_definite_bytestring();

  // Fake having a huge chunk of data
  unsigned char *data = malloc(1);
  cbor_bytestring_set_handle(item, data, UINT32_MAX);

  assert_int_equal(cbor_serialize(item, buffer, 512), 0); // fails to serialze due to size_t overflow
  assert_int_equal(cbor_serialized_size(item), (uint64_t)UINT32_MAX + 5);
    // fails: cbor_serialized_size() returns size_t, can't return more than UINT32_MAX
    // `(uint64_t)UINT32_MAX + 5` always exceeds UINT32_MAX.
  cbor_decref(&item);
}

Aside: assert_int_equal() is a bit suspicious as it uses 32-bit int comparison. Is is intentional?

To Reproduce

On i686-linux run cmake .. && make test.

Expected behavior

tests should pass

Environment

• libcbor version: 0.10.0, 0.10.1, git
• and build configuration flags (or source package version if using a package manager): libcbor> cmake flags: -DCMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY=OFF -DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_LOCALEDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/share/locale -DCMAKE_INSTALL_LIBEXECDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/libexec -DCMAKE_INSTALL_LIBDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/lib -DCMAKE_INSTALL_DOCDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/share/doc/libcbor -DCMAKE_INSTALL_INFODIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/share/info -DCMAKE_INSTALL_MANDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/share/man -DCMAKE_INSTALL_OLDINCLUDEDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/include -DCMAKE_INSTALL_INCLUDEDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/include -DCMAKE_INSTALL_SBINDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/sbin -DCMAKE_INSTALL_BINDIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/bin -DCMAKE_INSTALL_NAME_DIR=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0/lib -DCMAKE_POLICY_DEFAULT_CMP0025=NEW -DCMAKE_OSX_SYSROOT= -DCMAKE_FIND_FRAMEWORK=LAST -DCMAKE_STRIP=/nix/store/9hi79llhgx643mrfc5sz85fz5kzamz7k-gcc-wrapper-13.0.0/bin/strip -DCMAKE_RANLIB=/nix/store/9hi79llhgx643mrfc5sz85fz5kzamz7k-gcc-wrapper-13.0.0/bin/ranlib -DCMAKE_AR=/nix/store/9hi79llhgx643mrfc5sz85fz5kzamz7k-gcc-wrapper-13.0.0/bin/ar -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DCMAKE_INSTALL_PREFIX=/nix/store/76k0gib6bagdgy8lc1j6m7rr9xn2qcik-libcbor-0.10.0 -DCMAKE_INSTALL_LIBDIR=lib -DBUILD_SHARED_LIBS=on -DWITH_TESTS=ON