Compilation failure on macOS (M1) with Clang

[thomas-brunel]

Hi,

I'm typically working on open-ocpp using my Linux laptop and haven't encountered any issues during compilation. However, I recently tried building the project on my M1 MacBook and ran into some compilation errors using Clang.

Here is the relevant portion of the output:

Starting clang build...
...
[ 52%] Built target config
In file included from /Users/thomasbrunel/Documents/Perso/open-ocpp/src/tools/json/JsonValidator.cpp:19:
/Users/thomasbrunel/Documents/Perso/open-ocpp/src/tools/json/JsonValidator.h:54:17: error: implicit instantiation of undefined template 'std::basic_string<char>'
   54 |     std::string m_last_error;
      |                 ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.5.sdk/usr/include/c++/v1/__fwd/string.h:43:28: note: template is declared here
   43 | class _LIBCPP_TEMPLATE_VIS basic_string;
      |                            ^
1 error generated.
make[3]: *** [src/tools/json/CMakeFiles/json.dir/JsonValidator.cpp.o] Error 1
make[2]: *** [src/tools/json/CMakeFiles/json.dir/all] Error 2
make[2]: *** Waiting for unfinished jobs....
/Users/thomasbrunel/Documents/Perso/open-ocpp/src/websockets/libwebsockets/LibWebsocketServer.cpp:318:26: error: variable length arrays in C++ are a Clang extension [-Werror,-Wvla-cxx-extension]
  318 |                 char uri[lws_hdr_total_length(wsi, WSI_TOKEN_GET_URI) + 1];
      |                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/thomasbrunel/Documents/Perso/open-ocpp/src/websockets/libwebsockets/LibWebsocketServer.cpp:318:47: note: function parameter 'wsi' with unknown value cannot be used in a constant expression
  318 |                 char uri[lws_hdr_total_length(wsi, WSI_TOKEN_GET_URI) + 1];
      |                                               ^
/Users/thomasbrunel/Documents/Perso/open-ocpp/src/websockets/libwebsockets/LibWebsocketServer.cpp:265:51: note: declared here
  265 | int LibWebsocketServer::eventCallback(struct lws* wsi, enum lws_callback_reasons reason, void* user, void* in, size_t len)
      |                                                   ^
/Users/thomasbrunel/Documents/Perso/open-ocpp/src/websockets/libwebsockets/LibWebsocketServer.cpp:448:22: error: variable length arrays in C++ are a Clang extension [-Werror,-Wvla-cxx-extension]
  448 |             char uri[lws_hdr_total_length(wsi, WSI_TOKEN_GET_URI) + 1];
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/thomasbrunel/Documents/Perso/open-ocpp/src/websockets/libwebsockets/LibWebsocketServer.cpp:448:43: note: function parameter 'wsi' with unknown value cannot be used in a constant expression
  448 |             char uri[lws_hdr_total_length(wsi, WSI_TOKEN_GET_URI) + 1];
      |                                           ^
/Users/thomasbrunel/Documents/Perso/open-ocpp/src/websockets/libwebsockets/LibWebsocketServer.cpp:265:51: note: declared here
  265 | int LibWebsocketServer::eventCallback(struct lws* wsi, enum lws_callback_reasons reason, void* user, void* in, size_t len)
      |                                                   ^
2 errors generated.
make[3]: *** [src/websockets/CMakeFiles/ws.dir/libwebsockets/LibWebsocketServer.cpp.o] Error 1
make[2]: *** [src/websockets/CMakeFiles/ws.dir/all] Error 2
make[1]: *** [all] Error 2
make: *** [clang] Error 2

I’ve fixed these issues locally and verified that the build works correctly on both macOS (Clang) and Linux (GCC).

For completeness, I encountered two additional issues after resolving the ones above:

1. The use of sprintf in the doctest library is flagged by Clang; it should be replaced with snprintf.
2. A usage of WEXITSTATUS on the result of a system call directly (i.e., on a temporary value) causes an error.

Since doctest is a third-party library, I’m not planning to submit a PR for it unless you're open to vendor-side changes. As for the three other issues, I plan to open PRs for each of the errors.

Let me know how you'd like to proceed!

Thanks,
Thomas

[c-jimenez]

Hi,

Thanks for the bugs reporting and the associated PRs.
For the doctest issue, I would prefere not to update the source code of 3rd party libraries. Please submit an issue to the doctest maintainers. As a workaroud, we can disable the corresponding warning for the unit test builds until it is fixed on doctest's side.

[thomas-brunel]

Hi @c-jimenez,

With pleasure.

Regarding Doctest, I tested the new v2.4.12 using both Clang and GCC and didn’t encounter any issues, as they’ve removed the section that included sprintf. I’ve pushed the changes to a branch on my fork and can open a PR if you're okay with this solution.

Thanks,
Thomas

[c-jimenez]

Yes thanks, this seems the best solution for this issue.

[thomas-brunel]

Before creating the PR, I wanted to make sure everything was in order and noticed that version v2.4.12 requires a minimum CMake version of 3.5. This is higher than what's listed in your prerequisites and your CMakeLists.txt, which means users of the library may need to upgrade their CMake version, especially if you want your CMakeLists.txt to match doctest's requirement.
On the other hand, version v2.4.11 sets the minimum to 3.0.
I did a quick test with Clang on v2.4.11 and haven’t encountered any issues so far, I still need to test with GCC.
I'll wait for your feedback to know what you’d prefer to do about this before opening the PR.

[c-jimenez]

The prerequisite for open ocpp is CMake 3.13 or greater so if doctest needs at least CMake 3.5 it should not interfere.

[c-jimenez]

Since all the issues raised here have been resolved in your PRs, I close this ticket.
Thanks for your contributions.