Date: Sat, 20 Feb 2016 12:51:03 +0000 From: David Chisnall <theraven@FreeBSD.org> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: freebsd-toolchain@freebsd.org Subject: Re: confusing messages from clang Message-ID: <F3FF5389-DDEC-4D26-B004-FE3596021BE8@FreeBSD.org> In-Reply-To: <20160220005749.GA84382@troutmask.apl.washington.edu> References: <20160220005749.GA84382@troutmask.apl.washington.edu>
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C compilers are always doing best effort attempts to report when you =
feed them code that is not valid C.
For example, in this case:
On 20 Feb 2016, at 00:57, Steve Kargl <sgk@troutmask.apl.washington.edu> =
wrote:
> if (i > 0)
> goto corrupt;
This is valid, as long as you have a label called corrupt to look for. =
You do not, however, because:
> return;
>=20
> whoops:
> printf("whoops\n");
> return
>=20
> corrupt:
> printf("corrupt\n=E2=80=9D);
The statement:
> return corrupt: printf("corrupt\n");
is just confusing. It appears to be trying to return the value in =
corrupt (which is not an identifier that corresponds to any valid =
variable) and then has some trailing characters after the end of the =
statement. Fortunately, the compiler tells you exactly what is wrong:
First it says:
> foo.c:21:1: error: use of undeclared identifier 'corrupt'; did you =
mean 'crypt'?
> corrupt:
> ^~~~~~~
Here, it is telling you that the value passed to your return statement =
is an undeclared identifier. Then it tells you that you have more =
tokens after the end of your return statement:
> foo.c:21:8: error: expected ';' after return statement
> corrupt:
> ^
> ;
I am slightly surprised that there=E2=80=99s no warning that a return =
statement with a value is invalid in a function that returns void, but =
perhaps that=E2=80=99s because after finding two things wrong with one =
statement it gives up.
The correct fix, of course, is to insert the missing semicolon after the =
return at the end of line 19. If you had tried compiling the same thing =
with gcc 5, then you would have noticed that you get very similar error =
messages (though gcc doesn=E2=80=99t attempt to provide a fixit hint and =
does warn that you have a return statement returning a value from a =
function that returns void).
David
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