On 5/11/2022 12:27 PM, Masahiro Yamada wrote:

On Thu, May 12, 2022 at 3:48 AM Nick Desaulniers
[off-list ref] wrote:

quoted

On Mon, May 9, 2022 at 11:57 PM Masahiro Yamada [off-list ref] wrote:

quoted

quoted

quoted

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)

Sorry, I still do not understand your suggestion.


Could you provide me with a code diff
showing how to do this better?

I think you are doing exactly what he's asking for:
declare it with extern in the header (modpost.h change)
define it in one source file (modpost.c change)