Re: [PATCH] security_sk_free void return fixup

[Dick Streefland]

Linus Torvalds <torvalds@xxxxxxxx> wrote:
| I'm going to remove this warning from sparse. Apparently it is valid C99, 
| and somebody (I think Richard Henderson) made the excellent point that it 
| allows for type-independent code where you do something like
| 
| 	mytype myfunc1(xxx);
| 
| 	mytype myfunc2(xxx)
| 	{
| 		...
| 		return myfunc1(...);
| 	}
| 
| and it just works regardless of what type it is. 

It may work in gcc, but it is invalid according to ISO C99. First
sentence from section 6.8.6.4:

  A return statement with an expression shall not appear in a
  function whose return type is void.

Now, a function call is obviously an expression.

| sparse will obviously warn about expressions with non-void types being 
| returned from a void function, but the case where the expression exists 
| and has the right type should be ok.
| 
| I'm not sure it's wonderful C in general, but I certainly can't claim it 
| is actively offensive, and since gcc accepts it and we have these things 
| in the kernel, why complain? 

Gcc warns about this with the -pedantic option:

  $ gcc-3.3 -pedantic -c return.c
  return.c: In function `myfunc2':
  return.c:5: warning: `return' with a value, in function returning void

-- 
Dick Streefland                      ////                      Altium BV
dick.streefland@xxxxxxxxx           (@ @)          http://www.altium.com
--------------------------------oOO--(_)--OOo---------------------------

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