Re: [PATCH 2/2] test/hash: Fix warning in preprocessor symbol evaluation

From: George Spelvin
Date: Sun May 29 2016 - 14:54:10 EST


Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> Some versions of gcc don't like tests for the value of an undefined
> preprocessor symbol, even in the #else branch of an #ifndef:

Damn, I had hoped that would work universally; I tried to avoid the
uglier #if-inside-#ifdef construction. GCC 6 is quite happy wth it.

But no objections.

If you want:
Acked-by: George Spelvin <linux@xxxxxxxxxxxxxxxxxxx>

But here's an alternative. Geert, what do you think of this?

diff --git a/lib/test_hash.c b/lib/test_hash.c
index c9549c8b..8ea1d2ca 100644
--- a/lib/test_hash.c
+++ b/lib/test_hash.c
@@ -221,17 +221,17 @@ test_hash_init(void)
/* Issue notices about skipped tests. */
#ifndef HAVE_ARCH__HASH_32
pr_info("__hash_32() has no arch implementation to test.");
-#elif HAVE_ARCH__HASH_32 != 1
+#elif HAVE_ARCH__HASH_32 + 0 != 1
pr_info("__hash_32() is arch-specific; not compared to generic.");
#endif
#ifndef HAVE_ARCH_HASH_32
pr_info("hash_32() has no arch implementation to test.");
-#elif HAVE_ARCH_HASH_32 != 1
+#elif HAVE_ARCH_HASH_32 + 0 != 1
pr_info("hash_32() is arch-specific; not compared to generic.");
#endif
#ifndef HAVE_ARCH_HASH_64
pr_info("hash_64() has no arch implementation to test.");
-#elif HAVE_ARCH_HASH_64 != 1
+#elif HAVE_ARCH_HASH_64 + 0 != 1
pr_info("hash_64() is arch-specific; not compared to generic.");
#endif