linux-kernel - [PATCH] selftests: harness: Rework is_signed_type() to avoid collision with overflow.h

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Message-ID: <20250624231930.583689-1-seanjc@google.com>
Date: Tue, 24 Jun 2025 16:19:30 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Kees Cook <kees@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Vincent Mailhol <mailhol.vincent@...adoo.fr>, Arnaldo Carvalho de Melo <acme@...hat.com>, 
	Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH] selftests: harness: Rework is_signed_type() to avoid
 collision with overflow.h

Rename is_signed_type() to is_signed_var() to avoid colliding with a macro
of the same name defined by linux/overflow.h.  Note, overflow.h's version
takes a type as the input, whereas the harness's version takes a variable!

This fixes warnings (and presumably potential test failures) in tests
that utilize the selftests harness and happen to (indirectly) include
overflow.h.

  In file included from tools/include/linux/bits.h:34,
                   from tools/include/linux/bitops.h:14,
                   from tools/include/linux/hashtable.h:13,
                   from include/kvm_util.h:11,
                   from x86/userspace_msr_exit_test.c:11:
  tools/include/linux/overflow.h:31:9: error: "is_signed_type" redefined [-Werror]
     31 | #define is_signed_type(type)       (((type)(-1)) < (type)1)
        |         ^~~~~~~~~~~~~~
  In file included from include/kvm_test_harness.h:11,
                   from x86/userspace_msr_exit_test.c:9:
  ../kselftest_harness.h:754:9: note: this is the location of the previous definition
    754 | #define is_signed_type(var)       (!!(((__typeof__(var))(-1)) < (__typeof__(var))1))
        |         ^~~~~~~~~~~~~~

Opportunistically use is_signed_type() to implement is_signed_var() so
that the relationship and differences are obvious.

Fixes: fc92099902fb ("tools headers: Synchronize linux/bits.h with the kernel sources")
Cc: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---

This is probably compile-tested only, I don't think any of the KVM selftests
utilize the harness's EXPECT macros.

 tools/testing/selftests/kselftest_harness.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
index 2925e47db995..f3e7a46345db 100644
--- a/tools/testing/selftests/kselftest_harness.h
+++ b/tools/testing/selftests/kselftest_harness.h
@@ -56,6 +56,7 @@
 #include <asm/types.h>
 #include <ctype.h>
 #include <errno.h>
+#include <linux/overflow.h>
 #include <linux/unistd.h>
 #include <poll.h>
 #include <stdbool.h>
@@ -751,7 +752,7 @@
 	for (; _metadata->trigger; _metadata->trigger = \
 			__bail(_assert, _metadata))
 
-#define is_signed_type(var)       (!!(((__typeof__(var))(-1)) < (__typeof__(var))1))
+#define is_signed_var(var)	is_signed_type(__typeof__(var))
 
 #define __EXPECT(_expected, _expected_str, _seen, _seen_str, _t, _assert) do { \
 	/* Avoid multiple evaluation of the cases */ \
@@ -759,7 +760,7 @@
 	__typeof__(_seen) __seen = (_seen); \
 	if (!(__exp _t __seen)) { \
 		/* Report with actual signedness to avoid weird output. */ \
-		switch (is_signed_type(__exp) * 2 + is_signed_type(__seen)) { \
+		switch (is_signed_var(__exp) * 2 + is_signed_var(__seen)) { \
 		case 0: { \
 			uintmax_t __exp_print = (uintmax_t)__exp; \
 			uintmax_t __seen_print = (uintmax_t)__seen; \

base-commit: 78f4e737a53e1163ded2687a922fce138aee73f5
-- 
2.50.0.714.g196bf9f422-goog