C define function in header file

But if the inline function is a public member function a. This is so that all of the other modules that use the class can see the code they need to have placed inline by the compiler. Of course, placing the body of any function inside a header file conflicts with GAPP for the C programming language. This is consistent with Rule 4. IF, however, the inline function operates on the abstract data type defined in the header file and must be visible to two or more modules, THEN put the body of the inline function inside the header file.

There is no rule in the Embedded C Coding Standard that strictly prohibits this, so there is no conflict. See my earlier post What Belongs in a C. Tags: programming , standards. This entry was posted on Monday, March 21st, at am and is filed under Coding Standards. You can follow any responses to this entry through the RSS 2.

You can skip to the end and leave a response. Pinging is currently not allowed. Very nice answer. Specially when most of the students and me, I must admit, had the bad habit of filling the code with macros, when inlining is a much more elegant and safe resource.

If you -do- come up with such a rare scenario, you are writing some extremely performance-critical algorithm. In some cases, this can be a lot of files, so we have some effective methods to reduce external dependencies like forward declarations to classes that let us use pointers to objects of a class without including what could be a big tree of include files. Statements that generate data and code as they are parsed, should not be in a.

As far as my point of view is concerned, a header file should only have the minimum practical interface to a corresponding. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Learn more. What should and what shouldn't be in a header file? Asked 9 years, 3 months ago. Active 3 years, 6 months ago. Viewed k times. Improve this question. Walter Moshe Magnes Moshe Magnes 1, 1 1 gold badge 8 8 silver badges 6 6 bronze badges. Short and painless: definitions and declartions that are needed in more than one module. Marking this question as "too broad" and closing is an absolute shamefull overkill of moderation.

This question exactly asks what i am looking for - the Question is well formed and does ask a very clear question: what are the best practices? If this is "too broad" for softwareengineering.. TL; DR. I know you tagged the question to C, but some of the advices are also applicable. I think this is a good question Add a comment. Active Oldest Votes. What to put in headers: The minimal set of include directives that are needed to make the header compilable when the header is included in some source file.

Preprocessor symbol definitions of things that need to be shared and that can only accomplished via the preprocessor. Even in C, preprocessor symbols are best kept to a minimum.

Forward declarations of structures that are needed to make the structure definitions, function prototypes, and global variable declarations in the body of the header compilable. Definitions of data structures and enumerations that are shared amongst multiple source files. Declarations for functions and variables whose definitions will be visible to the linker. In the inline case, there may be multiple definitions, but there's a single function in the program.

In practical terms, the linker will remove all but one definition ignoring actual inlining, which is orthogonal and there will be a guarantee that if there's an out of line definition it will be unique single address. In the case of static there will be N functions, each with its own address, each with each own copies of any local static variables, those are different functions.

Show 2 more comments. EDIT: Next example demonstrates why functions and variables shouldn't be defined into unnamed namespace in headers : ops. What looks like a function in a header is actually many functions in different translation units, it will generate extra code larger binary, worse performance of the instruction cache , and if the function contains local static variables, each translation unit will refer to it's own version. The compiler will do that and be happy.

But whoever needs to debug that in the future will not be so happy. Puppy Puppy k 34 34 gold badges silver badges bronze badges. TonyK: While I agree to the suggestion of not using abbrevatons and using the full notations,I strongly disagree with the OP obviously isn't an expert. Well, I decided to delete my comment, but too late So let me restate it here: Using an abbreviation like TU assumes a level of experience in your reader that renders your explanation superfluous.

Unless, apparently, your reader is FredOverflow. Jer Jer 88 7 7 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Ask Question. Asked 3 years, 10 months ago. Active 8 months ago. Viewed 8k times. The setup If I have a program like this A header file that declares my main library function, primary and defines a short simple helper function, helper.

Please post the error message of the compiler. Add a comment. Active Oldest Votes. Jonathan Leffler k gold badges silver badges bronze badges.

Mickael B. Note that there are no prototypes in the header. There are function declarations, but the function declarations simply say that the functions take an indeterminate argument list but not a variable argument list like printf — such functions require an explicit prototype and do not specify the prototype.