CODEWITHSUNDEEP
cembedded
embedded_guy
embedded_guy

Reputation: 1967

What is the purpose of using #ifdef _LANGUAGE_C in VisualDSP++?

I am modifying some code for a Blackfin processor using VisualDSP++ v. 5.0. I have noticed that all of the header files in this project utilize the following convention:

#ifdef _LANGUAGE_C

/* All of the code associated with this header file. */

#endif

After searching through the documentation for this compiler I found the following:

_LANGUAGE_C - Always defined as 1.

So my question is two-fold.

  1. What is the purpose of using #ifdef _LANGUAGE_C?
  2. Wouldn't this just keep your code from running on a different compiler that may not have a macro defined for _LANGUAGE_C?

Upvotes: 1

Views: 468

Answers (3)

Clifford
Clifford

Reputation: 93524

You have to look at how it is used in context, however I believe that in this case it is used in headers that are used in both C code and assembler where the assembler code utilises the C pre-processor. It allows C headers to be included in assembler code, and have the preprocessor remove the C code specific elements.

For example it is useful in assembler code to have the same #define ... constant macro values as the C code to avoid duplication and inconsistency, but a struct definition or function prototype for example would be meaningless.

I would expect perhaps:#if defined(_LANGUAGE_C) || defined(_LANGUAGE_C_PLUS_PLUS), but if the documentation says that it is always defined, perhaps it is defined for both C and C++ compilation in your case.

Upvotes: 3

Kinjal Patel
Kinjal Patel

Reputation: 405

It is called a compilation constant, such compilation constant must be added to your build environment, you should check your build environment. It is to tell the compiler that the code it going to compile are to compiled with C specific checks and will generate outfut file(hex or bin) depending on that.

Upvotes: 1

Ryan
Ryan

Reputation: 2815

To answer your compound question, the answer is yes, for the most part. This is part of some pre processor directives that allow you to build for different environments using the same code. If you look through the windows driver kit for example, you see this convention utilized all over the place to ensure that the most efficient code is build depending on the target environment and compiler. I hope this is helpful. The could have potentially added code in there after the #ifdef with another for _LANGUAGE_CPP and put C++ specific code in there etc etc.

Upvotes: 1

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