#include in C++ works, but not in C

Question

A single-line test.c:

#include <dwrite.h>

From the visual studio command prompt,

compiled as C++ works: cl /c /Tp test.c

compiled as C does not: cl /c test.c

First, I get a bunch of errors as this one:

C:\Program Files (x86)\Windows Kits\10\\include\10.0.19041.0\\um\dwrite.h(671): error C2059: syntax error: ':'

The line 671 is as follows:

interface DWRITE_DECLARE_INTERFACE("739d886a-cef5-47dc-8769-1a8b41bebbb0") IDWriteFontFile : public IUnknown

preprocessed to C++

struct __declspec(uuid("739d886a-cef5-47dc-8769-1a8b41bebbb0")) __declspec(novtable) IDWriteFontFile : public IUnknown

preprocessed to C

struct   IDWriteFontFile : public IUnknown

and the part " : public IUnknown" gets in the way. How am I supposed to fix this?

Then I get an error on line 1037: error C2061: syntax error: identifier 'IDWriteGeometrySink'

interface ID2D1SimplifiedGeometrySink;
typedef ID2D1SimplifiedGeometrySink IDWriteGeometrySink;

preprocessed to C

struct ID2D1SimplifiedGeometrySink;
typedef ID2D1SimplifiedGeometrySink IDWriteGeometrySink;

Finally, a bunch of errors involving static_cast which C does not have.

All in all, is dwrite.h not suitable for C? Using Visual Studio Community 2022. Does it work in any previous versions?

"Wrappers for Direct2D are written in C++." from the page you linked. — stark, Apr 15 '22 at 10:45

score 0 · Answer 1 · answered Apr 15 '22 at 10:24

0

C doesn't have inheritance, so this header is most likely C++ only.

The project you linked uses D2D from .cpp files and wraps C++ interface into C.

answered Apr 15 '22 at 10:24

arrowd

How? If you look into window.c, the first thing it does is #include "window.h", which then #includes "dwritewrapper.h", which #includes . I don't understand how that is a wrapper. CPP files call directX functions, but C files pass parameters to those CPP functions (say, DWRITE_FONT_WEIGHT_NORMAL in window.c). And DWRITE_FONT_WEIGHT_NORMAL is defined in dwrite.h as enum. – aleksazr Apr 15 '22 at 13:55
@aleksazr like it's been said already, you can't use dwrite.h from SDK with C code, it's not meant for that, as it's using C++ constructs. Specific workarounds that some projects use are unrelated to directwrite itself, you should consult project source. – bunglehead Apr 16 '22 at 05:12

1 Answers1