* [PATCH v3 1/2] Documentation: coding-style: ask function-like macros to evaluate parameters
2024-03-22 8:49 [PATCH v3 0/2] codingstyle: avoid unused parameters for a function-like macro Barry Song
@ 2024-03-22 8:49 ` Barry Song
2024-03-22 14:33 ` Mark Brown
2024-03-22 8:49 ` [PATCH v3 2/2] scripts: checkpatch: Check unused parameters for function-like macro Barry Song
1 sibling, 1 reply; 4+ messages in thread
From: Barry Song @ 2024-03-22 8:49 UTC (permalink / raw)
To: corbet, workflows, linux-doc, apw, joe, dwaipayanray1, lukas.bulwahn
Cc: linux-kernel, Barry Song, Andrew Morton, Chris Zankel,
Huacai Chen, Herbert Xu, Guenter Roeck, Stephen Rothwell,
Mark Brown, Max Filippov
From: Barry Song <v-songbaohua@oppo.com>
Recent commit 77292bb8ca69c80 ("crypto: scomp - remove memcpy if
sg_nents is 1 and pages are lowmem") leads to warnings on xtensa
and loongarch,
In file included from crypto/scompress.c:12:
include/crypto/scatterwalk.h: In function 'scatterwalk_pagedone':
include/crypto/scatterwalk.h:76:30: warning: variable 'page' set but not used [-Wunused-but-set-variable]
76 | struct page *page;
| ^~~~
crypto/scompress.c: In function 'scomp_acomp_comp_decomp':
>> crypto/scompress.c:174:38: warning: unused variable 'dst_page' [-Wunused-variable]
174 | struct page *dst_page = sg_page(req->dst);
|
The reason is that flush_dcache_page() is implemented as a noop
macro on these platforms as below,
#define flush_dcache_page(page) do { } while (0)
The driver code, for itself, seems be quite innocent and placing
maybe_unused seems pointless,
struct page *dst_page = sg_page(req->dst);
for (i = 0; i < nr_pages; i++)
flush_dcache_page(dst_page + i);
And it should be independent of architectural implementation
differences.
Let's provide guidance on coding style for requesting parameter
evaluation or proposing the migration to a static inline
function.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mark Brown <broonie@kernel.org>
Suggested-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
---
Documentation/process/coding-style.rst | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index 9c7cf7347394..791d333a57fd 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -827,6 +827,22 @@ Macros with multiple statements should be enclosed in a do - while block:
do_this(b, c); \
} while (0)
+Function-like macros with unused parameters should be replaced by static
+inline functions to avoid the issue of unused variables:
+
+.. code-block:: c
+
+ static inline void fun(struct foo *foo)
+ {
+ }
+
+For historical reasons, many files still use the cast to (void) to evaluate
+parameters, but this method is not recommended:
+
+.. code-block:: c
+
+ #define macrofun(foo) do { (void) (foo); } while (0)
+
Things to avoid when using macros:
1) macros that affect control flow:
--
2.34.1
^ permalink raw reply [flat|nested] 4+ messages in thread* [PATCH v3 2/2] scripts: checkpatch: Check unused parameters for function-like macro
2024-03-22 8:49 [PATCH v3 0/2] codingstyle: avoid unused parameters for a function-like macro Barry Song
2024-03-22 8:49 ` [PATCH v3 1/2] Documentation: coding-style: ask function-like macros to evaluate parameters Barry Song
@ 2024-03-22 8:49 ` Barry Song
1 sibling, 0 replies; 4+ messages in thread
From: Barry Song @ 2024-03-22 8:49 UTC (permalink / raw)
To: corbet, workflows, linux-doc, apw, joe, dwaipayanray1, lukas.bulwahn
Cc: linux-kernel, Xining Xu, Andrew Morton, Chris Zankel,
Huacai Chen, Herbert Xu, Guenter Roeck, Stephen Rothwell,
Mark Brown, Barry Song
From: Xining Xu <ma.xxn@outlook.com>
If function-like macros do not utilize a parameter, it might result in a
build warning. In our coding style guidelines, we advocate for utilizing
static inline functions to replace such macros. This patch verifies
compliance with the new rule.
For a macro such as the one below,
#define test(a) do { } while (0)
The test result is as follows.
ERROR: Parameter 'a' is not used in function-like macro, please use static
inline instead
#21: FILE: mm/init-mm.c:20:
+#define test(a) do { } while (0)
total: 1 errors, 0 warnings, 8 lines checked
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Xining Xu <ma.xxn@outlook.com>
Tested-by: Barry Song <v-songbaohua@oppo.com>
---
scripts/checkpatch.pl | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 9c4c4a61bc83..6f778f3403b5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6109,6 +6109,30 @@ sub process {
WARN("TRAILING_SEMICOLON",
"macros should not use a trailing semicolon\n" . "$herectx");
}
+
+ if ($dstat =~ /^\+\s*#\s*define\s+$Ident\s*(\((?:[^\(\)]++|(?-1))*\))\s+(\S+.*)(\/\/.*)?/) {
+ my $params = $1 || "";
+ my $body = $2 || "";
+
+ # get the individual params
+ $params =~ tr/()//d;
+ # remove leading and trailing whitespace
+ $params =~ s/^\s+|\s+$//g;
+
+ $ctx =~ s/\n*$//;
+ my $cnt = statement_rawlines($ctx);
+ my $herectx = get_stat_here($linenr, $cnt, $here);
+
+ if ($params ne "") {
+ my @paramList = split /,\s*/, $params;
+ foreach my $param(@paramList) {
+ if ($body !~ /\b$param\b/) {
+ ERROR("UNUSED_PARAM_IN_MACRO",
+ "Parameter '$param' is not used in function-like macro, please use static inline instead\n" . "$herectx");
+ }
+ }
+ }
+ }
}
# check for redundant bracing round if etc
--
2.34.1
^ permalink raw reply [flat|nested] 4+ messages in thread