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Date:   Sat, 20 Mar 2021 11:54:24 +0100
From:   Fabio Aiuto <fabioaiuto83@gmail.com>
To:     gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        apw@canonical.com, joe@perches.com
Subject: CHECKPATCH: missing a warning soon after include files decl -c
Message-ID: <20210320105424.GA3698@agape.jhs>
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User-Agent: Mutt/1.10.1 (2018-07-13)
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Hi,

here's an issue in checkpatch.pl

$ perl script/checkpatch.pl -f drivers/staging/rtl8723bs/core/rtw_ap.c

I get three warning related to an extern declaration

WARNING: externs should be avoided in .c files
#14: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:14:
+extern unsigned char WMM_OUI[];
--
WARNING: externs should be avoided in .c files
#15: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:15:
+extern unsigned char WPS_OUI[];
--
WARNING: externs should be avoided in .c files
#16: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:16:
+extern unsigned char P2P_OUI[];
----------------------

but the file checked has 4 extern declaration:
-----------------------------
#define _RTW_AP_C_

#include <drv_types.h>
#include <rtw_debug.h>
#include <asm/unaligned.h>

extern unsigned char RTW_WPA_OUI[];
extern unsigned char WMM_OUI[];
extern unsigned char WPS_OUI[];
extern unsigned char P2P_OUI[];

void init_mlme_ap_info(struct adapter *padapter)
-------------------------------

If I add a ';' this way:
----------------------------
#define _RTW_AP_C_

#include <drv_types.h>
#include <rtw_debug.h>
#include <asm/unaligned.h>
;
extern unsigned char RTW_WPA_OUI[];
extern unsigned char WMM_OUI[];
extern unsigned char WPS_OUI[];
extern unsigned char P2P_OUI[];

void init_mlme_ap_info(struct adapter *padapter)
--------------------------------

the missing warning appears:
----------------------------------
WARNING: externs should be avoided in .c files
#13: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:13:
+extern unsigned char RTW_WPA_OUI[];
--
WARNING: externs should be avoided in .c files
#14: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:14:
+extern unsigned char WMM_OUI[];
--
WARNING: externs should be avoided in .c files
#15: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:15:
+extern unsigned char WPS_OUI[];
--
WARNING: externs should be avoided in .c files
#16: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:16:
+extern unsigned char P2P_OUI[];
-------------------------------------------
Applying this ugly patch to debug:

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index df8b23dc1eb0..ecbbb731361c 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6810,6 +6810,11 @@ sub process {
 		{
 			WARN("AVOID_EXTERNS",
 			     "externs should be avoided in .c files\n" .  $herecurr);
+		} elsif ($realfile =~ /\.c$/ && defined $stat &&
+		    $stat =~ /extern\s+/)
+		{
+			WARN("AVOID_EXTERNS",
+			     "print stat value\n" .  $stat);
 		}
 
 # check for function declarations that have arguments without identifier names

--------------
I get:

WARNING: print stat value
+#include <XXXXXXXXXXX>
 #include <XXXXXXXXXXX>
 #include <XXXXXXXXXXXXXXX>
 
 extern unsigned char RTW_WPA_OUI[];
WARNING: externs should be avoided in .c files
#14: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:14:
+extern unsigned char WMM_OUI[];

WARNING: externs should be avoided in .c files
#15: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:15:
+extern unsigned char WPS_OUI[];

WARNING: externs should be avoided in .c files
#16: FILE: drivers/staging/rtl8723bs/core/rtw_ap.c:16:
+extern unsigned char P2P_OUI[];

I don't know if it's best to fix the regex of the particular "extern in .c files issue"
or maybe how the statement is computed. Should a statement represent a single line?

Suggestions are welcome,

fabio