[RESOLVED] inline vs __inline

[John E]

Somebody's sent me some code where one of the header files contains a function looking like this:-

static inline int32_t the_function_name()
{
      // the function body
}

I tried building this with MSVC-8 but it doesn't like inline - however, it's happy if I precede it with a couple of underscores:-

static __inline int32_t the_function_name()
{
      // the function body
}

What's interesting is that in both cases, inline and __inline get printed in blue (i.e. the compiler recognises them as keywords) but it must interpret them to mean something different. I just wondered if anyone knows what the difference is?

[VictorN]

Inline Functions (C++)

[John E]

A great link Victor, thanks. Here's what I learned...

The inline keyword is available only in C++. The __inline and __forceinline keywords are available in both C and C++.

I think that explains it !!

[VictorN]

Exactly!

[wolle]

A great link Victor, thanks. Here's what I learned...

"The inline keyword is available only in C++."

That's not quite true, inline has been part of C since version C99 (which is the C version that C++ 11 builds on).

But inline in C and C++ differ slightly and I suppose the Microsoft specific __inline keyword has been introduced to equalize this difference to some common inlining functionality that Microsoft finds useful in a mixed C/C++ situation.

So inline is defined by the C and C++ standards whereas __inline is vendor specific (in this case Microsoft) and defined by that vendor. Personally I think one should stick to the standards even when it means a little more effort.

[2kaud]

As the link in Victor's post #2 says,

The inline keyword is available only in C++.

If you are using MS VS to compile c programs (as opposed to c++), note that their c compiler doesn't implement all of the c standard (since c99)- and is not likely to as MS sees their VS as c++ with c being very much a poorer relation. If you need a c total compliant compiler then you'll need to look elsewhere.