kunit: remove format func from struct kunit_assert, get it to 0 bytes

Each calll to a KUNIT_EXPECT_*() macro creates a local variable which
contains a struct kunit_assert.

Normally, we'd hope the compiler would be able to optimize this away,
but we've seen cases where it hasn't, see
https://groups.google.com/g/kunit-dev/c/i3fZXgvBrfA/m/GbrMNej2BAAJ.

In changes like commit 21957f90b28f ("kunit: split out part of
kunit_assert into a static const"), we've moved more and more parts out
of struct kunit_assert and its children types (kunit_binary_assert).

This patch removes the final field and gets us to:
  sizeof(struct kunit_assert) == 0
  sizeof(struct kunit_binary_assert) == 24 (on UML x86_64).

This also reduces the amount of macro plumbing going on at the cost of
passing in one more arg to the base KUNIT_ASSERTION macro and
kunit_do_failed_assertion().

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

2 files changed, 17 insertions, 28 deletions

diff --git a/include/kunit/assert.h b/include/kunit/assert.h
index 4b52e12c2ae8..ace3de8d1ee7 100644
--- a/include/kunit/assert.h
+++ b/include/kunit/assert.h
@@ -42,16 +42,15 @@ struct kunit_loc {
 
 /**
  * struct kunit_assert - Data for printing a failed assertion or expectation.
- * @format: a function which formats the data in this kunit_assert to a string.
  *
  * Represents a failed expectation/assertion. Contains all the data necessary to
  * format a string to a user reporting the failure.
  */
-struct kunit_assert {
-	void (*format)(const struct kunit_assert *assert,
-		       const struct va_format *message,
-		       struct string_stream *stream);
-};
+struct kunit_assert {};
+
+typedef void (*assert_format_t)(const struct kunit_assert *assert,
+				const struct va_format *message,
+				struct string_stream *stream);
 
 void kunit_assert_prologue(const struct kunit_loc *loc,
 			   enum kunit_assert_type type,
@@ -72,16 +71,6 @@ void kunit_fail_assert_format(const struct kunit_assert *assert,
 			      struct string_stream *stream);
 
 /**
- * KUNIT_INIT_FAIL_ASSERT_STRUCT - Initializer for &struct kunit_fail_assert.
- *
- * Initializes a &struct kunit_fail_assert. Intended to be used in
- * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
- */
-#define KUNIT_INIT_FAIL_ASSERT_STRUCT {					\
-	.assert = { .format = kunit_fail_assert_format },		\
-}
-
-/**
  * struct kunit_unary_assert - Represents a KUNIT_{EXPECT|ASSERT}_{TRUE|FALSE}
  * @assert: The parent of this type.
  * @condition: A string representation of a conditional expression.
@@ -110,7 +99,6 @@ void kunit_unary_assert_format(const struct kunit_assert *assert,
  * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
  */
 #define KUNIT_INIT_UNARY_ASSERT_STRUCT(cond, expect_true) {		       \
-	.assert = { .format = kunit_unary_assert_format },		       \
 	.condition = cond,						       \
 	.expected_true = expect_true					       \
 }
@@ -145,7 +133,6 @@ void kunit_ptr_not_err_assert_format(const struct kunit_assert *assert,
  * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
  */
 #define KUNIT_INIT_PTR_NOT_ERR_STRUCT(txt, val) {			       \
-	.assert = { .format = kunit_ptr_not_err_assert_format },	       \
 	.text = txt,							       \
 	.value = val							       \
 }
@@ -190,7 +177,6 @@ void kunit_binary_assert_format(const struct kunit_assert *assert,
  * KUNIT_INIT_BINARY_ASSERT_STRUCT() - Initializes a binary assert like
  *	kunit_binary_assert, kunit_binary_ptr_assert, etc.
  *
- * @format_func: a function which formats the assert to a string.
  * @text_: Pointer to a kunit_binary_assert_text.
  * @left_val: The actual evaluated value of the expression in the left slot.
  * @right_val: The actual evaluated value of the expression in the right slot.
@@ -200,11 +186,9 @@ void kunit_binary_assert_format(const struct kunit_assert *assert,
  * fields but with different types for left_val/right_val.
  * This is ultimately used by binary assertion macros like KUNIT_EXPECT_EQ, etc.
  */
-#define KUNIT_INIT_BINARY_ASSERT_STRUCT(format_func,			       \
-					text_,				       \
+#define KUNIT_INIT_BINARY_ASSERT_STRUCT(text_,				       \
 					left_val,			       \
 					right_val) {			       \
-	.assert = { .format = format_func },				       \
 	.text = text_,							       \
 	.left_value = left_val,						       \
 	.right_value = right_val					       \
diff --git a/include/kunit/test.h b/include/kunit/test.h
index 20cc4770cb3f..57a653f6a008 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -473,9 +473,10 @@ void kunit_do_failed_assertion(struct kunit *test,
 			       const struct kunit_loc *loc,
 			       enum kunit_assert_type type,
 			       const struct kunit_assert *assert,
+			       assert_format_t assert_format,
 			       const char *fmt, ...);
 
-#define KUNIT_ASSERTION(test, assert_type, pass, assert_class, INITIALIZER, fmt, ...) do { \
+#define KUNIT_ASSERTION(test, assert_type, pass, assert_class, assert_format, INITIALIZER, fmt, ...) do { \
 	if (unlikely(!(pass))) {					       \
 		static const struct kunit_loc __loc = KUNIT_CURRENT_LOC;       \
 		struct assert_class __assertion = INITIALIZER;		       \
@@ -483,6 +484,7 @@ void kunit_do_failed_assertion(struct kunit *test,
 					  &__loc,			       \
 					  assert_type,			       \
 					  &__assertion.assert,		       \
+					  assert_format,		       \
 					  fmt,				       \
 					  ##__VA_ARGS__);		       \
 	}								       \
@@ -494,7 +496,8 @@ void kunit_do_failed_assertion(struct kunit *test,
 			assert_type,					       \
 			false,						       \
 			kunit_fail_assert,				       \
-			KUNIT_INIT_FAIL_ASSERT_STRUCT,			       \
+			kunit_fail_assert_format,			       \
+			{},						       \
 			fmt,						       \
 			##__VA_ARGS__)
 
@@ -525,6 +528,7 @@ void kunit_do_failed_assertion(struct kunit *test,
 			assert_type,					       \
 			!!(condition) == !!expected_true,		       \
 			kunit_unary_assert,				       \
+			kunit_unary_assert_format,			       \
 			KUNIT_INIT_UNARY_ASSERT_STRUCT(#condition,	       \
 						       expected_true),	       \
 			fmt,						       \
@@ -582,8 +586,8 @@ do {									       \
 			assert_type,					       \
 			__left op __right,				       \
 			assert_class,					       \
-			KUNIT_INIT_BINARY_ASSERT_STRUCT(format_func,	       \
-							&__text,	       \
+			format_func,					       \
+			KUNIT_INIT_BINARY_ASSERT_STRUCT(&__text,	       \
 							__left,		       \
 							__right),	       \
 			fmt,						       \
@@ -640,8 +644,8 @@ do {									       \
 			assert_type,					       \
 			strcmp(__left, __right) op 0,			       \
 			kunit_binary_str_assert,			       \
-			KUNIT_INIT_BINARY_ASSERT_STRUCT(kunit_binary_str_assert_format,\
-							&__text,	       \
+			kunit_binary_str_assert_format,			       \
+			KUNIT_INIT_BINARY_ASSERT_STRUCT(&__text,	       \
 							__left,		       \
 							__right),	       \
 			fmt,						       \
@@ -660,6 +664,7 @@ do {									       \
 			assert_type,					       \
 			!IS_ERR_OR_NULL(__ptr),				       \
 			kunit_ptr_not_err_assert,			       \
+			kunit_ptr_not_err_assert_format,		       \
 			KUNIT_INIT_PTR_NOT_ERR_STRUCT(#ptr,		       \
 						      __ptr),		       \
 			fmt,						       \