Inline keyword not recognized in c module compiled inside a cpp project (VS2005)

Question

I am developing an embedded C application in a C90-compliant compiler which, on the other hand, for testing and debugging purposes, is deployed in Matlab/Simulink interfacing the application with a CPP file. This bundle is compiled instead with Matlab MEX, which is configured to use Visual Studio 2005 to build.

This means we have one CPP file, and a couple of .C/.H files that are built altogether. This workflow has been successful for me, using the #ifdef __cplusplus extern "C" {...} trick on each C call.

However, I have come with a problem when the need of inline functions arose due to time constraints in the embedded application.

Next, SSCCE built in VS2005:

main.cpp

#include "c_method.h"

void main()
{
    for(int b = 0; b < 9; b++)
    int a = c_method(b);
}

c_method.c

#include "c_method.h"

inline int inline_fun(int x)
{
    return x+1;
}

int c_method(int b)
{
    return inline_fun(b);
}

c_method.h

#ifndef __C_METHOD_H__
#define __C_METHOD_H__

int c_method(int b);

#endif

Which provides the following errors:

c_method.c(7) : error C2054: expected '(' to follow 'inline'
c_method.c(8) : error C2085: 'inline_fun' : not in formal parameter list
c_method.c(8) : error C2143: syntax error : missing ';' before '{' 

I noticed I missed extern "C" {...} but did not work either.

As read here in SO, changing c_method.c to c_method.cpp will do the trick, however I'd rather have an alternative solution, if exists any, as I'm not very confident about the embedded C compiler accepting the cpp extension without coming whining to me...

Thank you.

Added

@πάντα ῥεῖ got with the answer. Creating an empty declaration of inline will do the trick.

However, as @Lundin suggests, I'll meditate the possibility of using another C compiler for the PC platform build.

Answer 1

Visual studio doesn't support the inline keyword in C, because it does not implement C99 (which introduced that keyword).

However, it does support the Microsoft-specific keyword __inline in both C and C++. To make your code portable, you can do this:

#include "c_method.h"

#ifdef _MSC_VER
  #define inline __inline
#endif

inline int inline_fun(int x)
{
    return x+1;
}

int c_method(int b)
{
    return inline_fun(b);
}

Of course, in practice, you'd put the inline definition into a shared header file.

Answer 2

There is no inline keyword in C90, so that would be why it doesn't work. It seems rather unlikely that a C compiler will compile C++. Visual Studio only does it because it is a C++ compiler, not a C compiler.

You have to check the embedded compiler for compiler extensions to the language. There is usually a compiler option you can enable.

Answer 3

I don't think in Visual Studio, inline function can be defined in a .c or .cpp file. You may try to move the definition of the inline function into the header file.