Compile error: token is not a valid binary operator in a preprocessor subexpression

[YanzhaoW]

Hi,

I'm using the clang with libc++ to build my project using stdexec. I have compiled and installed stdexec, but when I consume the library in my project, I get lots of errors during the compilation (using the example main.cpp):

/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:20:23: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:137:33: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:293:69: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:381:68: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:392:47: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:425:53: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:439:57: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:447:75: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:453:64: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:459:64: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__config.hpp:491:85: error: token is not a valid binary operator in a preprocessor subexpression
In file included from /home/yanwang/test/cpp/stdexec/main.cpp:1:
In file included from /home/yanwang/software/stdexec/include/exec/static_thread_pool.hpp:20:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/execution.hpp:18:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__execution_fwd.hpp:19:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__meta.hpp:24:
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__concepts.hpp:18:26: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__concepts.hpp:28:60: error: token is not a valid binary operator in a preprocessor subexpression
In file included from /home/yanwang/test/cpp/stdexec/main.cpp:1:
In file included from /home/yanwang/software/stdexec/include/exec/static_thread_pool.hpp:20:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/execution.hpp:18:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__execution_fwd.hpp:19:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__meta.hpp:26:
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__utility.hpp:177:57: error: token is not a valid binary operator in a preprocessor subexpression
In file included from /home/yanwang/test/cpp/stdexec/main.cpp:1:
In file included from /home/yanwang/software/stdexec/include/exec/static_thread_pool.hpp:20:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/execution.hpp:21:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__as_awaitable.hpp:24:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__receivers.hpp:22:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__env.hpp:21:
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__cpo.hpp:85:68: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__cpo.hpp:93:51: error: token is not a valid binary operator in a preprocessor subexpression
In file included from /home/yanwang/test/cpp/stdexec/main.cpp:1:
In file included from /home/yanwang/software/stdexec/include/exec/static_thread_pool.hpp:20:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/execution.hpp:21:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__as_awaitable.hpp:24:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__receivers.hpp:22:
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__env.hpp:581:46: error: token is not a valid binary operator in a preprocessor subexpression
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__env.hpp:626:46: error: token is not a valid binary operator in a preprocessor subexpression
In file included from /home/yanwang/test/cpp/stdexec/main.cpp:1:
In file included from /home/yanwang/software/stdexec/include/exec/static_thread_pool.hpp:20:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/execution.hpp:30:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__ensure_started.hpp:26:
In file included from /home/yanwang/software/stdexec/include/exec/../stdexec/__detail/__shared.hpp:31:
/home/yanwang/software/stdexec/include/exec/../stdexec/__detail/../stop_token.hpp:28:61: error: token is not a valid binary operator in a preprocessor subexpression

I looked a little bit deeper and found that the error is caused the "digital separator" in the macros, which somehow my clang compiler doesn't support:

#if defined(__cpp_explicit_this_parameter) && (__cpp_explicit_this_parameter >= 2021'10L)
#  define STDEXEC_EXPLICIT_THIS() 1
#else
#  define STDEXEC_EXPLICIT_THIS() 0
#endif

Here if I change 2021'10L to 202110L, the error would be fixed.

I download the clang compiler directly from their apt repos: https://apt.llvm.org

My CMake options are:

cmake -DCMAKE_CXX_COMPILER=$(which clang-20) -DCMAKE_C_COMPILER=$(which clang-20) -DCMAKE_CXX_FLAGS="-stdlib=libc++" ..

[Insomniac-Ossifrage]

Hello,
I’ve encountered the same issue. It appears to be related to clang-scan-deps, I've found a couple of issue reports on the LLVM repository:

• [clang-scan-deps] Error if integer literal contains a single quote in #if directive llvm/llvm-project#88896
• [clang-scan-deps] IntegerLiteralSeparator breaks preprocessing conditionals with digit separators llvm/llvm-project#145189

There seems to be a pull-request with a fix underway. So far I'm getting around this issue by disabling module scanning in CMake with set(CMAKE_CXX_SCAN_FOR_MODULES OFF)