[Issue 24509] New: importC cannot handle _stdcall Function Calling Convention with single heading underscore

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24509

          Issue ID: 24509
           Summary: importC cannot handle _stdcall Function Calling
                    Convention with single heading underscore
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: aferust at gmail.com

In Windows programming, the stdcall calling convention is usually specified
using the __stdcall keyword or macro. The import c documentation also lists
__stdcall calling convention with double underscores. However, there are some
occurrences in c library headers using single underscores. For instance,
Microsoft's onnx runtime [1]. This kind of usage is not handled with importc.
Importc yields a syntax error for these situations, such as:

onnxruntime_c_api.h(288,25): Error: expected identifier for declarator
onnxruntime_c_api.h(288,25): Error: `;` or `,` expected

1:
https://github.com/microsoft/onnxruntime/blob/08d208b969fec6e7f6505f4f468eea0d6a9031c2/include/onnxruntime/core/session/onnxruntime_c_api.h#L86

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