From: Emil Velikov <emil.l.velikov@gmail.com>
Date: Mon, 30 Sep 2024 20:06:14 +0000 (+0100)
Subject: shared: introduce uadd32_overflow() helper
X-Git-Tag: v34~248
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8808f0eeaaafee0e0e9e59671829c7fec55108a8;p=thirdparty%2Fkmod.git

shared: introduce uadd32_overflow() helper

We'll use it in the upcoming size_t variant.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/169
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
---

diff --git a/meson.build b/meson.build
index 1c87fe0e..eb5cfadd 100644
--- a/meson.build
+++ b/meson.build
@@ -49,6 +49,7 @@ endforeach
 _builtins = [
   ['__builtin_clz', '0', true],
   ['__builtin_types_compatible_p', 'int, int', true],
+  ['__builtin_uadd_overflow', '0U, 0U, (void*)0', false],
   ['__builtin_uaddl_overflow', '0UL, 0UL, (void*)0', false],
   ['__builtin_uaddll_overflow', '0ULL, 0ULL, (void*)0', false],
 ]
diff --git a/shared/util.h b/shared/util.h
index 6fa4bf43..87c72796 100644
--- a/shared/util.h
+++ b/shared/util.h
@@ -92,6 +92,16 @@ static inline void freep(void *p)
 }
 #define _cleanup_free_ _cleanup_(freep)
 
+static inline bool uadd32_overflow(uint32_t a, uint32_t b, uint32_t *res)
+{
+#if (HAVE___BUILTIN_UADD_OVERFLOW && __SIZEOF_INT__ == 4)
+	return __builtin_uadd_overflow(a, b, res);
+#else
+	*res = a + b;
+	return UINT32_MAX - a < b;
+#endif
+}
+
 static inline bool uadd64_overflow(uint64_t a, uint64_t b, uint64_t *res)
 {
 #if (HAVE___BUILTIN_UADDL_OVERFLOW && __SIZEOF_LONG__ == 8)
diff --git a/testsuite/test-util.c b/testsuite/test-util.c
index ce246d39..1f968606 100644
--- a/testsuite/test-util.c
+++ b/testsuite/test-util.c
@@ -191,6 +191,23 @@ DEFINE_TEST(test_write_str_safe,
 		},
 	});
 
+static int test_uadd32_overflow(const struct test *t)
+{
+	uint32_t res;
+	bool overflow;
+
+	overflow = uadd32_overflow(UINT32_MAX - 1, 1, &res);
+	assert_return(!overflow, EXIT_FAILURE);
+	assert_return(res == UINT32_MAX, EXIT_FAILURE);
+
+	overflow = uadd32_overflow(UINT32_MAX, 1, &res);
+	assert_return(overflow, EXIT_FAILURE);
+
+	return EXIT_SUCCESS;
+}
+DEFINE_TEST(test_uadd32_overflow,
+	    .description = "check implementation of uadd32_overflow()")
+
 static int test_uadd64_overflow(const struct test *t)
 {
 	uint64_t res;