| Message ID | 1473246420-1035-1-git-send-email-baoyou.xie@linaro.org |
|---|---|
| State | Accepted |
| Commit | 72e8d5fdf58b7d398b31612e63cc376f43c9da1b |
| Headers | show |
On Wednesday, September 7, 2016 11:37:07 AM CEST Yuval Mintz wrote: > > We get 4 warnings when building kernel with W=1: > > drivers/net/ethernet/qlogic/qed/qed_selftest.c:6:5: warning: no previous > > prototype for 'qed_selftest_memory' [-Wmissing-prototypes] > > drivers/net/ethernet/qlogic/qed/qed_selftest.c:19:5: warning: no previous > > prototype for 'qed_selftest_interrupt' [-Wmissing-prototypes] > > drivers/net/ethernet/qlogic/qed/qed_selftest.c:32:5: warning: no previous > > prototype for 'qed_selftest_register' [-Wmissing-prototypes] > > drivers/net/ethernet/qlogic/qed/qed_selftest.c:55:5: warning: no previous > > prototype for 'qed_selftest_clock' [-Wmissing-prototypes] > > > > In fact, these functions are declared in qed_selftest.h, so this patch add missing > > header dependencies. > > > > Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org> > > While I obviously have no strong objection for including qed_selftest.h > from qed_selftest.c, I'm not sure I understand which C standard dictates > this requirement. > Why should a function definition [not call] be preceded by a prototype? This rule addresses two problems: - some functions should be marked static as they are never used outside of the file that declares them. Marking them static give the compiler better opportunities for optimization and lets you see when a function becomes unused, and if there is no external declaration that is often an indication that there are no other users. - When a function is defined in one file and used in another, you want both files to include the same header that has the declaration to ensure that the types are identical. There are cases where the prototype is changed after the fact in an incompatible way, causing silent data corruption on some configurations but maybe not on others. Arnd
On Wednesday, September 7, 2016 12:31:03 PM CEST Yuval Mintz wrote: > > > While I obviously have no strong objection for including > > > qed_selftest.h from qed_selftest.c, I'm not sure I understand which C > > > standard dictates this requirement. > > > Why should a function definition [not call] be preceded by a prototype? > > > > - When a function is defined in one file and used in another, you want > > both files to include the same header that has the declaration to > > ensure that the types are identical. There are cases where the > > prototype is changed after the fact in an incompatible way, causing > > silent data corruption on some configurations but maybe not on others. > > O.k., motivation is clear. > But this really isn't enforced by the ansi-c standard, right? No, ansi-c doesn't enforce this, and even the regular kernel build flags don't enable the warning in question, we only get it when either building with "make C=1" using sparse, or "make W=1" to enable extra warnings from gcc. The warning is however really useful, and I hope that we go through all drivers in the kernel and eliminate these warnings in order to turn them on by default for all drivers. > Acked-by: Yuval Mintz <Yuval.Mintz@qlogic.com> Thanks, Arnd
From: Baoyou Xie <baoyou.xie@linaro.org> Date: Wed, 7 Sep 2016 19:07:00 +0800 > We get 4 warnings when building kernel with W=1: > drivers/net/ethernet/qlogic/qed/qed_selftest.c:6:5: warning: no previous prototype for 'qed_selftest_memory' [-Wmissing-prototypes] > drivers/net/ethernet/qlogic/qed/qed_selftest.c:19:5: warning: no previous prototype for 'qed_selftest_interrupt' [-Wmissing-prototypes] > drivers/net/ethernet/qlogic/qed/qed_selftest.c:32:5: warning: no previous prototype for 'qed_selftest_register' [-Wmissing-prototypes] > drivers/net/ethernet/qlogic/qed/qed_selftest.c:55:5: warning: no previous prototype for 'qed_selftest_clock' [-Wmissing-prototypes] > > In fact, these functions are declared in qed_selftest.h, so this patch > add missing header dependencies. > > Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org> Applied.
diff --git a/drivers/net/ethernet/qlogic/qed/qed_selftest.c b/drivers/net/ethernet/qlogic/qed/qed_selftest.c index a342bfe..9b7678f 100644 --- a/drivers/net/ethernet/qlogic/qed/qed_selftest.c +++ b/drivers/net/ethernet/qlogic/qed/qed_selftest.c @@ -2,6 +2,7 @@ #include "qed_dev_api.h" #include "qed_mcp.h" #include "qed_sp.h" +#include "qed_selftest.h" int qed_selftest_memory(struct qed_dev *cdev) {
We get 4 warnings when building kernel with W=1: drivers/net/ethernet/qlogic/qed/qed_selftest.c:6:5: warning: no previous prototype for 'qed_selftest_memory' [-Wmissing-prototypes] drivers/net/ethernet/qlogic/qed/qed_selftest.c:19:5: warning: no previous prototype for 'qed_selftest_interrupt' [-Wmissing-prototypes] drivers/net/ethernet/qlogic/qed/qed_selftest.c:32:5: warning: no previous prototype for 'qed_selftest_register' [-Wmissing-prototypes] drivers/net/ethernet/qlogic/qed/qed_selftest.c:55:5: warning: no previous prototype for 'qed_selftest_clock' [-Wmissing-prototypes] In fact, these functions are declared in qed_selftest.h, so this patch add missing header dependencies. Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org> --- drivers/net/ethernet/qlogic/qed/qed_selftest.c | 1 + 1 file changed, 1 insertion(+) -- 2.7.4