From: Nick Desaulniers <ndesaulniers@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nicolas Schier <nicolas@fjasle.eu>,
Peter Zijlstra <peterz@infradead.org>,
linux-modules <linux-modules@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Ard Biesheuvel <ardb@kernel.org>,
Sami Tolvanen <samitolvanen@google.com>,
clang-built-linux <llvm@lists.linux.dev>
Subject: Re: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c
Date: Wed, 11 May 2022 11:47:56 -0700 [thread overview]
Message-ID: <CAKwvOdmK4oH0t8Q6F19sWKX1fT=AgS=kfvn05FT01HffLJwgMQ@mail.gmail.com> (raw)
In-Reply-To: <CAK7LNARGNEDzPPUsPjDXsXUUUPSFK2erQRuyPocR_v5hTYRihg@mail.gmail.com>
On Mon, May 9, 2022 at 11:57 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > > index a78b75f0eeb0..e7e2c70a98f5 100644
> > > --- a/scripts/mod/modpost.c
> > > +++ b/scripts/mod/modpost.c
> > > @@ -31,7 +31,7 @@ static bool external_module;
> > > /* Only warn about unresolved symbols */
> > > static bool warn_unresolved;
> > >
> > > -static int sec_mismatch_count;
> > > +int sec_mismatch_count;
> >
> > ^ this should go in modpost.h if it is to be used in two translation
> > units, rather than forward declaring it in section-check.c. You did
> > this for the functions.
>
>
> Sorry, I do not understand.
>
>
> In modpost.h, I put the declaration:
>
> extern int sec_mismatch_count;
>
> If I moved it to the header without 'extern'
> I would get multiple definitions.
Yeah, you need to _declare_ it w/ extern in the header, then _define_
it in one source file.
That way, if the type ever changes, the sources will agree on type in
all source files. You will get a redefinition error if the definition
changes the type of the variable since the last declaration.
What you're doing is forward declaring, which works, and is a common
pattern for (bloated) C++, but is less type safe than sharing a single
common declaration between multiple source files via a single common
shared header. (Sorry I didn't respond before you sent v5)
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2022-05-11 18:48 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-08 19:06 [PATCH v4 00/14] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 01/14] modpost: remove left-over cross_compile declaration Masahiro Yamada
2022-05-09 17:08 ` Nick Desaulniers
2022-05-12 4:35 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 02/14] modpost: change the license of EXPORT_SYMBOL to bool type Masahiro Yamada
2022-05-12 4:36 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c Masahiro Yamada
2022-05-09 17:19 ` Nick Desaulniers
2022-05-10 6:55 ` Masahiro Yamada
2022-05-11 18:47 ` Nick Desaulniers [this message]
2022-05-11 19:27 ` Masahiro Yamada
2022-05-11 19:51 ` Jeff Johnson
2022-05-11 20:01 ` Nick Desaulniers
2022-05-08 19:06 ` [PATCH v4 04/14] modpost: add sym_find_with_module() helper Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 05/14] modpost: extract symbol versions from *.cmd files Masahiro Yamada
2022-05-09 21:52 ` Sami Tolvanen
2022-05-08 19:06 ` [PATCH v4 06/14] kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS Masahiro Yamada
2022-05-09 17:50 ` Nick Desaulniers
2022-05-10 13:03 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 07/14] kbuild: stop merging *.symversions Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 08/14] genksyms: adjust the output format to modpost Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 09/14] kbuild: do not create *.prelink.o for Clang LTO or IBT Masahiro Yamada
2022-05-09 23:13 ` Sami Tolvanen
2022-05-08 19:06 ` [PATCH v4 10/14] kbuild: check static EXPORT_SYMBOL* by script instead of modpost Masahiro Yamada
2022-05-09 18:05 ` Nick Desaulniers
2022-05-10 13:53 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 11/14] kbuild: make built-in.a rule robust against too long argument error Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 12/14] kbuild: make *.mod " Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 13/14] kbuild: add cmd_and_savecmd macro Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 14/14] kbuild: rebuild multi-object modules when objtool is updated Masahiro Yamada
2022-05-09 4:24 ` [PATCH v4 00/14] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
2022-05-09 22:13 ` Nathan Chancellor
2022-05-10 6:55 ` Masahiro Yamada
2022-05-09 22:19 ` Nathan Chancellor
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