mirror of https://github.com/rusefi/rusefi.git
99 lines
2.1 KiB
C++
99 lines
2.1 KiB
C++
/*
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* test_cpp_memory_layout.cpp
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*
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* Jun 15, 2019
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* @author Andrey Belomutskiy, (c) 2012-2020
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*/
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#include "unit_test_framework.h"
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// in C++ struct is pretty much a class just fields are public by default
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struct TestParent {
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int field0 = 540;
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float field1 = 333.33;
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};
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class TestPlainChild: public TestParent {
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public:
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float getSum();
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};
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class TestPlainChildExtraFields: public TestParent {
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public:
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float field3 = 35555;
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float field4 = 45555;
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};
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float TestPlainChild::getSum() {
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return field0 + field1;
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}
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class TestChildWithVirtual: public TestParent {
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public:
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virtual float getSumVirtual() {
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return field0 + field1;
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}
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};
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TEST(misc, cppPlainStructMemoryLayout) {
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TestPlainChild c;
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// validate field initializers just for fun
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ASSERT_EQ(540, c.field0);
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ASSERT_NEAR(333.33, c.field1, EPS4D);
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ASSERT_EQ(sizeof(c), sizeof(TestParent));
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int destimationInt = 1;
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// no virtual table since nothing virtual on TestPlainChild
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memcpy(&destimationInt, &c, 4);
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ASSERT_EQ(540, destimationInt);
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ASSERT_EQ((uintptr_t)&c.field0, (uintptr_t)&c);
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}
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static int valueWePointAt;
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TEST(misc, cppVirtualStructMemoryLayout) {
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TestChildWithVirtual c;
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int pointerSize = sizeof(int*);
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// '4' in case of 32 bit target
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// '8' in case of 64 bit target
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int MAGIC_VTABLE_SIZE = pointerSize;
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// validate field initializers just for fun
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ASSERT_EQ(540, c.field0);
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ASSERT_NEAR(333.33, c.field1, EPS4D);
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ASSERT_EQ(sizeof(c), sizeof(TestParent) + MAGIC_VTABLE_SIZE);
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int destimationInt = 1;
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memcpy(&destimationInt, &c, 4);
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ASSERT_NE(540, destimationInt);
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// static_cast is smart to skip the vtable, we like static_cast
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TestParent *parent = static_cast<TestParent*>(&c);
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ASSERT_EQ((uintptr_t)&c.field0, (uintptr_t)parent);
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ASSERT_EQ(MAGIC_VTABLE_SIZE, (uintptr_t)&c.field0 - (uintptr_t)&c);
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}
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TEST(misc, cppPlainExtraFieldsStructMemoryLayout) {
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TestPlainChildExtraFields c;
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ASSERT_EQ(sizeof(c), sizeof(TestParent) + 8);
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int destimationInt = 1;
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// parent fields go first
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memcpy(&destimationInt, &c, 4);
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ASSERT_EQ(540, destimationInt);
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ASSERT_EQ(0, (uintptr_t)&c.field0 - (uintptr_t)&c);
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}
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