Thread: subroutine in C

Originally Posted by Elysia

Sure, if you only provide a definition, then you must use void in the parameter list.

Not so. In a definition, an unnamed void argument, and an empty argument list both mean the same thing.

So this will not compile with a "too many arguments" error:

Code:

int func(){
  return 0;
}

int main(){
  func(1);
}

Originally Posted by King Mir

Not so. In a definition, an unnamed void argument, and an empty argument list both mean the same thing.

So this will not compile with a "too many arguments" error:

Not in VS2005

Originally Posted by vart

Not in VS2005

Are you sure you did not compile as C++? It works for me when compiling as C.

EDIT:
Wait a minute, I assumed that King Mir meant 'this will not (compile with a "too many arguments" error)' (which does not really make sense, I suppose), but maybe King Mir meant 'this will (not compile) with a "too many arguments" error', in which case the reason why this is not so is that the definition is also a declaration.

EDIT #2:
hmm... but the language of C99 seems to indicate otherwise:

Originally Posted by Section 6.7.5.3, Paragraph 14

An identifier list declares only the identifiers of the parameters of the function. An empty list in a function declarator that is part of a definition of that function specifies that the function has no parameters. The empty list in a function declarator that is not part of a definition of that function specifies that no information about the number or types of the parameters is supplied.

The wording "not part of a definition" seems to say that although a definition is a declaration, the fact that it is a definition trumps the fact that it is a declaration for the interpretation of an empty parameter list. If this is so (and also in C90), then gcc and MSVC are both non-conformant in this area.

I compiled it as C

VS2005 gives no errors
gcc port used in CodeBlocks - gives the error specified by King Mir

Originally Posted by vart

gcc port used in CodeBlocks - gives the error specified by King Mir

What is the version of gcc? The MinGW port of gcc 3.4.5 did not emit such an error for both C90 and C99 mode with -Wall and -pedantic tacked on.

Originally Posted by laserlight

What is the version of gcc? The MinGW port of gcc 3.4.5 did not emit such an error for both C90 and C99 mode with -Wall and -pedantic tacked on.

ok I played a little with the CodeBlocks installation to see exactly which gcc is configured, what switches are set, and finally - what command line it uses to compile a file.


Here is it:
1. gcc is 3.4.5 and it does not show the error. (I have running it from command prompt)
2. CodeBlocks on some reason starts g++ to compile the c-file


So - about the second - how do I tell to CodeBlocks that *.c files should be compiled as C and not C++?

Originally Posted by vart

So - about the second - how do I tell to CodeBlocks that *.c files should be compiled as C and not C++?

I think this might work: click on the .c file and select "Properties...". Click on the "Advanced" tab and change "CPP" to "CC" for the "Compiler variable" setting.

EDIT:
No, Code::Blocks does not seem smart enough to use gcc instead of g++ in that case.

Originally Posted by laserlight

The wording "not part of a definition" seems to say that although a definition is a declaration, the fact that it is a definition trumps the fact that it is a declaration for the interpretation of an empty parameter list. If this is so (and also in C90), then gcc and MSVC are both non-conformant in this area.

My take on the whole was:

Code:

void fun(void); // No parameters
void fun(); // No parameter information (infinite parameters)
void fun(void) { } // No parameters
void fun () { } // No parameters

I could be wrong, though.
Although VS would let the last example compile.