[C++20][Modules] Includes in module partitions

[SasisaDev]

module;

#include <cstdlib>

export module Types:Allocator;

export
template <typename ElementType>
class TAllocator {
public:
    static ElementType* Allocate(unsigned int sz) {
        return malloc(sz);
    }
};

export module Types;

export import :Allocator;

error: use of undeclared identifier 'malloc'; did you mean '_alloca'?
    return malloc(sz);
           ^~~~~~
           _alloca

If i move this implementation to main module, and not it's partition, code compiles.
If i use this code with other simmiliar modules, and they cross at some point, error becomes bigger.

In file included from D:\VisualStudio\VC\Tools\MSVC\14.34.31933\include\cstdlib:12:
In file included from C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\math.h:11:
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:16:1: error: unknown type name '_UCRT_DISABLE_CLANG_WARNINGS'
_UCRT_DISABLE_CLANG_WARNINGS
^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:18:20: error: expected ';' after top level declarator
_CRT_BEGIN_C_HEADER
                   ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:175:26: error: unknown type name '_In_'
void __cdecl _fperrraise(_In_ int _Except);
                         ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:177:1: error: unknown type name '_Check_return_'
_Check_return_ _ACRTIMP short __cdecl _dclass(_In_ double _X);
^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:177:24: error: expected ';' after top level declarator
_Check_return_ _ACRTIMP short __cdecl _dclass(_In_ double _X);
                       ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:177:47: error: unknown type name '_In_'
_Check_return_ _ACRTIMP short __cdecl _dclass(_In_ double _X);
                                              ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:178:1: error: unknown type name '_Check_return_'
_Check_return_ _ACRTIMP short __cdecl _ldclass(_In_ long double _X);
^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:178:24: error: expected ';' after top level declarator
_Check_return_ _ACRTIMP short __cdecl _ldclass(_In_ long double _X);
                       ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:178:48: error: unknown type name '_In_'
_Check_return_ _ACRTIMP short __cdecl _ldclass(_In_ long double _X);
                                               ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:179:1: error: unknown type name '_Check_return_'
_Check_return_ _ACRTIMP short __cdecl _fdclass(_In_ float _X);
^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:179:24: error: expected ';' after top level declarator
_Check_return_ _ACRTIMP short __cdecl _fdclass(_In_ float _X);
                       ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:179:48: error: unknown type name '_In_'
_Check_return_ _ACRTIMP short __cdecl _fdclass(_In_ float _X);
                                               ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:181:1: error: unknown type name '_Check_return_'
_Check_return_ _ACRTIMP int __cdecl _dsign(_In_ double _X);
^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:181:24: error: expected ';' after top level declarator
_Check_return_ _ACRTIMP int __cdecl _dsign(_In_ double _X);
                       ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:181:44: error: unknown type name '_In_'
_Check_return_ _ACRTIMP int __cdecl _dsign(_In_ double _X);
                                           ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:182:1: error: unknown type name '_Check_return_'
_Check_return_ _ACRTIMP int __cdecl _ldsign(_In_ long double _X);
^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:182:24: error: expected ';' after top level declarator
_Check_return_ _ACRTIMP int __cdecl _ldsign(_In_ long double _X);
                       ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:182:45: error: unknown type name '_In_'
_Check_return_ _ACRTIMP int __cdecl _ldsign(_In_ long double _X);
                                            ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_math.h:183:1: error: unknown type name '_Check_return_'
_Check_return_ _ACRTIMP int __cdecl _fdsign(_In_ float _X);
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

[llvmbot]

@llvm/issue-subscribers-clang-modules

[iains]

export module Types;

export impot :Allocator;

........^ ......
there seems to be a typo there?

[SasisaDev]

........^ ...... there seems to be a typo there?

It's my typo, cuz i rewrote this part manually here. In the code there's no typo, clang would've say me that i mistaken keyword.

[ChuanqiXu9]

Weird, I can't reproduce this locally.

I tried the following two commands:

clang++ -std=c++20 Part.cppm --precompile -o Types-Allocator.pcm
clang++ -std=c++20 main.cppm -fprebuilt-module-path=. -fsyntax-only

And I am wondering if it is the problem of windows, then I tried:

clang++ -std=c++20 -Xclang -triple -Xclang x86_64-windows-msvc Part.cppm --precompile -o Types-Allocator.pcm
clang++ -std=c++20 -Xclang -triple -Xclang x86_64-windows-msvc main.cppm -fprebuilt-module-path=. -fsyntax-only

but things look fine still.

[aaronmondal]

I suspect this to be the same underlying issue as #58540.

[JarrodBegnoche]

I'm having a similar issue when trying to include a header from opencv.

module;

#include <opencv2/core/types.hpp>

export module mod;

export cv::Scalar distance(cv::Scalar origin, cv::Scalar direction, double distance) {
    return origin + (direction * distance);
}

#include <format>
#include <iostream>

#include <opencv2/core/types.hpp>

import mod;

int main() {
    cv::Scalar origin(1.0, 2.0, 3.0, 1.0);
    cv::Scalar direction(2.0, 4.0, 5.0, 0.0);
    cv::Scalar sum = origin + direction;
    std::cout << std::format("Sum ({}, {}, {})", sum[0], sum[1], sum[2]) << std::endl;

    cv::Scalar end_point = distance(origin, direction, 2.0);
    std::cout << std::format("End Point ({}, {}, {})", end_point[0], end_point[1], end_point[2]) << std::endl;

    return 0;
}

$CXX -std=c++20 mod.cppm --precompile -I/usr/include/opencv4 -o mod.pcm
$CXX -std=c++20 main.cpp -I/usr/include/opencv4 -fprebuilt-module-path=. -fsyntax-only

The compilation will fail on the scalar addition:

main.cpp:11:29: error: invalid operands to binary expression ('cv::Scalar' (aka 'Scalar_<double>') and 'cv::Scalar')
    cv::Scalar sum = origin + direction;
                     ~~~~~~ ^ ~~~~~~~~~
/usr/include/opencv4/opencv2/core/types.hpp:1052:14: note: candidate template ignored: could not match 'Complex' against 'Scalar_'
Complex<_Tp> operator + (const Complex<_Tp>& a, const Complex<_Tp>& b)
             ^
/usr/include/opencv4/opencv2/core/types.hpp:1102:14: note: candidate template ignored: could not match 'Complex' against 'Scalar_'
Complex<_Tp> operator + (const Complex<_Tp>& a, _Tp b)
             ^
/usr/include/opencv4/opencv2/core/types.hpp:1112:14: note: candidate template ignored: could not match 'Complex' against 'Scalar_'
Complex<_Tp> operator + (_Tp b, const Complex<_Tp>& a)
             ^
/usr/include/opencv4/opencv2/core/types.hpp:1337:13: note: candidate template ignored: could not match 'Point_' against 'Scalar_'
Point_<_Tp> operator + (const Point_<_Tp>& a, const Point_<_Tp>& b)
            ^
/usr/include/opencv4/opencv2/core/types.hpp:1584:14: note: candidate template ignored: could not match 'Point3_' against 'Scalar_'
Point3_<_Tp> operator + (const Point3_<_Tp>& a, const Point3_<_Tp>& b)
             ^
/usr/include/opencv4/opencv2/core/types.hpp:1759:12: note: candidate template ignored: could not match 'Size_' against 'Scalar_'
Size_<_Tp> operator + (const Size_<_Tp>& a, const Size_<_Tp>& b)
           ^
/usr/include/opencv4/opencv2/core/types.hpp:1964:12: note: candidate template ignored: could not match 'Rect_' against 'Scalar_'
Rect_<_Tp> operator + (const Rect_<_Tp>& a, const Point_<_Tp>& b)
           ^
/usr/include/opencv4/opencv2/core/types.hpp:1976:12: note: candidate template ignored: could not match 'Rect_' against 'Scalar_'
Rect_<_Tp> operator + (const Rect_<_Tp>& a, const Size_<_Tp>& b)
           ^
1 error generated.

This is reduced as much as I could. I originally ran into the issue when having multiple module partitions both include opencv and one imports the other. In the above example, if you move the opencv include to after import mod it will work but that isn't an option in module partitions.

$CXX --version
clang version 16.0.3
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/clang/latest/bin

[ChuanqiXu9]

Is the operator static? I suspect this fall into #61807

[koplas]

@SasisaDev I am unable to reproduce this on Windows MSVC clang 17 0d3eee3, it compiles for me without errors. Can you provide the preprocessor output and the command line flags you used?