[comp.lang.c++] Inline Isn't

kevin@msa3b.UUCP (Kevin P. Kleinfelter) (06/05/91)

When one declares a class in a .h file, and specifies the body of
a member function as inline in the .cpp file, do most compilers fail
to inline it?

i.e. In the following code, is it too much to expect that "f.bar()" gets
inlined? This would require a smart linker.



/**** foo.h ******/
class foo {
private:
int x;
public:
   int bar ();
};

/***** foo.cpp ****/
inline int bar ()
{
   return x;
}

/***** other.cpp *****/
#include "foo.h"
void demo (void)
{
int i;
foo f;

   i = f.bar();
}
-- 
Kevin Kleinfelter @ DBS, Inc (404) 239-2347   ...gatech!nanoVX!msa3b!kevin

Dun&Bradstreet Software, 3445 Peachtree Rd, NE, Atlanta GA 30326-1276

gary@matterhorn.ctc.contel.com (Gary Bisaga x4219) (06/05/91)

In article <1666@msa3b.UUCP>, kevin@msa3b.UUCP (Kevin P. Kleinfelter) writes:
> When one declares a class in a .h file, and specifies the body of
> a member function as inline in the .cpp file, do most compilers fail
> to inline it?
> 
> i.e. In the following code, is it too much to expect that "f.bar()" gets
> inlined? This would require a smart linker.
> [example of putting an inline function in another file]
Yes, but not because it's just the linker.  The ARM (don't have it handy,
so I can't remember the section reference) says that inline functions must
have internal linkage, i.e., be defined in the same source file where they're
used.

comeau@ditka.Chicago.COM (Greg Comeau) (06/06/91)

In article <1666@msa3b.UUCP> kevin@msa3b.UUCP (Kevin P. Kleinfelter) writes:
>When one declares a class in a .h file, and specifies the body of
>a member function as inline in the .cpp file, do most compilers fail
>to inline it?
>/**** foo.h ******/
>class foo { private: int x; public: int bar (); };
>/***** foo.cpp ****/
>inline int bar () { return x; }
>/***** other.cpp *****/
>#include "foo.h"
>void demo (void) { int i; foo f; i = f.bar(); }

First, recognize that inline is only a hint to the compiler (like register
is) and not a mandate.

Second, for something that's inline to have significance it must be
visible to the translation unit that wants it inline'd.

In a case like you've illustrated, one would typically put the definition
for bar right into the class definition, that way the function isn't just
a linker issue and is known to the compiler as an inline.

- Greg
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