CODEWITHSUNDEEP
c++cvisual-studio-2010
feelfree
feelfree

Reputation: 11763

cmath syntax errors when building a C wrapper for a C++ library

Now I am developing a C++ library, which is expect to have C interface. In order to do that I have two solutions:

Solution 1:

lib_c_header.h
lib_c_header_imp.cpp

Solution 2:

lib_c_header.h
  lib_c_header_imp.c

Then the first question I have is : is it valid to have a C interface header and C++ implementation file as a wrapper of the C++ library?

Then move to the second solution, I will create a C interface header and C implementation file. In the C implementation file, C++ classes from the library will be invoked. However, when I do that, I always have cmath syntax errors:

c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\cmath(19): error C2061: syntax error : identifier 'acosf'

These errors lead me to the following codes in the cmath file: 

_STD_BEGIN
using _CSTD acosf; using _CSTD asinf;
using _CSTD atanf; using _CSTD atan2f; using _CSTD ceilf;
using _CSTD cosf; using _CSTD coshf; using _CSTD expf;
using _CSTD fabsf; using _CSTD floorf; using _CSTD fmodf;
using _CSTD frexpf; using _CSTD ldexpf; using _CSTD logf;
using _CSTD log10f; using _CSTD modff; using _CSTD powf;
using _CSTD sinf; using _CSTD sinhf; using _CSTD sqrtf;
using _CSTD tanf; using _CSTD tanhf;

I think the problem comes from the fact that the implementation file lib_c_header_imp.c will be compiled as C file while in the file some C++ classes will be invoked. I was wondering whether there is a solution to this problem. Thanks.

Upvotes: 0

Views: 1285

Answers (2)

Jan Hudec
Jan Hudec

Reputation: 76346

The only way to write a C function that calls C++ is to compile it in C++ in an extern "C" block. Because the body of the function still has to be C++. So you'll have to have lib_c_header_imp.cpp.

You may either have separate header for the C wrapper and the full C++ interface or you may have them together in one header with the C++ part guarded by #ifdef __cplusplus. Depends on how big it is and how it will be most often used etc.

In the header you may only include C headers (i.e. <math.h> rather than <cmath>) or you may include C++ headers under #ifdef __cplusplus, but than you obviously can't use their content in the C wrapper part.

Upvotes: 3

user2656151
user2656151

Reputation:

Generally you can include C in C++, i.e. use a C++ compiler when compiling the source. However, you can not use a C compiler to compile C++ code.

Upvotes: 0

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