[PATCH] [v3] printf: fix errname.c list

[Arnd Bergmann]

From: Arnd Bergmann <arnd@xxxxxxxx>

On most architectures, gcc -Wextra warns about the list of error
numbers containing both EDEADLK and EDEADLOCK:

lib/errname.c:15:67: warning: initialized field overwritten [-Woverride-init]
   15 | #define E(err) [err + BUILD_BUG_ON_ZERO(err <= 0 || err > 300)] = "-" #err
      |                                                                   ^~~
lib/errname.c:172:2: note: in expansion of macro 'E'
  172 |  E(EDEADLK), /* EDEADLOCK */
      |  ^

On parisc, a similar error happens with -ECANCELLED, which is an
alias for ECANCELED.

Make the EDEADLK printing conditional on the number being distinct
from EDEADLOCK, and remove the -ECANCELLED bit completely as it
can never be hit.

To ensure these are correct, add static_assert lines that verify
all the remaining aliases are in fact identical to the canonical
name.

Fixes: 57f5677e535b ("printf: add support for printing symbolic error names")
Cc: Petr Mladek <pmladek@xxxxxxxx>
Suggested-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Acked-by: Uwe Kleine-König <uwe@xxxxxxxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Link: https://lore.kernel.org/all/20210514213456.745039-1-arnd@xxxxxxxxxx/
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
It looks I promised to resend this one in May but never did.
The patch is still useful, please apply.
---
 lib/errname.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/lib/errname.c b/lib/errname.c
index 05cbf731545f..67739b174a8c 100644
--- a/lib/errname.c
+++ b/lib/errname.c
@@ -21,6 +21,7 @@ static const char *names_0[] = {
 	E(EADDRNOTAVAIL),
 	E(EADV),
 	E(EAFNOSUPPORT),
+	E(EAGAIN), /* EWOULDBLOCK */
 	E(EALREADY),
 	E(EBADE),
 	E(EBADF),
@@ -31,15 +32,17 @@ static const char *names_0[] = {
 	E(EBADSLT),
 	E(EBFONT),
 	E(EBUSY),
-#ifdef ECANCELLED
-	E(ECANCELLED),
-#endif
+	E(ECANCELED), /* ECANCELLED */
 	E(ECHILD),
 	E(ECHRNG),
 	E(ECOMM),
 	E(ECONNABORTED),
+	E(ECONNREFUSED), /* EREFUSED */
 	E(ECONNRESET),
+	E(EDEADLK), /* EDEADLOCK */
+#if EDEADLK != EDEADLOCK /* mips, sparc, powerpc */
 	E(EDEADLOCK),
+#endif
 	E(EDESTADDRREQ),
 	E(EDOM),
 	E(EDOTDOT),
@@ -166,14 +169,17 @@ static const char *names_0[] = {
 	E(EUSERS),
 	E(EXDEV),
 	E(EXFULL),
-
-	E(ECANCELED), /* ECANCELLED */
-	E(EAGAIN), /* EWOULDBLOCK */
-	E(ECONNREFUSED), /* EREFUSED */
-	E(EDEADLK), /* EDEADLOCK */
 };
 #undef E
 
+#ifdef EREFUSED /* parisc */
+static_assert(EREFUSED == ECONNREFUSED);
+#endif
+#ifdef ECANCELLED /* parisc */
+static_assert(ECANCELLED == ECANCELED);
+#endif
+static_assert(EAGAIN == EWOULDBLOCK); /* everywhere */
+
 #define E(err) [err - 512 + BUILD_BUG_ON_ZERO(err < 512 || err > 550)] = "-" #err
 static const char *names_512[] = {
 	E(ERESTARTSYS),
-- 
2.29.2