GCC Code Coverage Report

Directory:	./
File:	TestVirtualDataPtr.cpp
Date:	2026-03-21 20:51:59

	Exec	Total	Coverage
Lines:	38	38	100.0%
Functions:	17	17	100.0%
Branches:	48	180	26.7%

  
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      // See [What is “virtual data,” and how-can / why-would I use it in C++?]
    
      // (https://isocpp.org/wiki/faq/value-vs-ref-semantics#virt-data)
    
      #include "StretchableArray.hpp"
    
      #include "Verbose.hpp"
    
      #include "compat/gsl14.hpp"
    
      #include "compat/memory14.hpp"
    
      class StackPtr {
    
      public:
    
          // The base class has a normal constructor that provides its own object.
    
          explicit StackPtr(gsl::index size = 1);
    
      public:
    
          void Push(double x);
    
          double Pop();
    
      protected:
    
          // The base class has a constructor that accepts an object from a derived class.
    
          StackPtr(std::unique_ptr<Array> data);
    
      private:
    
          // To simulate virtual data in C++, the base class has a pointer to the
    
          // member object and the base class’s destructor deletes the object.
    
          // Some additional memory allocation overhead is imposed.
    
          std::unique_ptr<Array> data_;
    
          gsl::index index_{0};
    
      };
    
      ////////////////////////////////////////////////////////////////////////////////
    
      // Virtual data makes the implementation of the derived class easier:
    
      // most of the implementation is inherited.
    
      class StretchableStackPtr : public StackPtr {
    
      public:
    
          // The derived class has a constructor that provides a new object to the base class.
    
          explicit StretchableStackPtr(gsl::index size = 1);
    
      };
    
      ////////////////////////////////////////////////////////////////////////////////
    
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      3
      StackPtr::StackPtr(gsl::index size) : StackPtr(std::make_unique<Array>(size)) {}
    
      8
      StackPtr::StackPtr(std::unique_ptr<Array> data) : data_{std::move(data)} {}
    
      11
      void StackPtr::Push(double x) {
    
      11
          (*data_)[index_++] = x; // may throw
    
      10
      }
    
      8
      double StackPtr::Pop() {
    
      8
          return (*data_)[--index_]; // may throw
    
      }
    
      ////////////////////////////////////////////////////////////////////////////////
    
      1
      StretchableStackPtr::StretchableStackPtr(gsl::index size) :
    
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      1
                  StackPtr{std::make_unique<StretchableArray>(size)} {}
    
      ////////////////////////////////////////////////////////////////////////////////
    
      #include <gtest/gtest.h>
    
      8
      TEST(VirtualDataPtr, Stack_Push_Pop) {
    
      2
          const auto size = gsl::index{3};
    
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      6
          auto stack = Verbose<StackPtr>{"stack", size};
    
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      8
          for (auto x = gsl::index{0}; x < size; x++) {
    
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      6
              stack.Push(gsl::narrow_cast<double>(x));
    
          }
    
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      8
          for (auto x = size - 1; x >= 0; x--) {
    
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      6
              EXPECT_EQ(gsl::narrow_cast<double>(x), stack.Pop());
    
          }
    
      4
      }
    
      8
      TEST(VirtualDataPtr, Stack_Push_Full) {
    
      2
          const auto size = gsl::index{3};
    
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          auto stack = Verbose<StackPtr>{"stack", size};
    
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      8
          for (auto x = gsl::index{0}; x < size; x++) {
    
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      6
              stack.Push(gsl::narrow_cast<double>(x));
    
          }
    
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      2
          EXPECT_THROW(stack.Push(gsl::narrow_cast<double>(size)), std::out_of_range);
    
      4
      }
    
      8
      TEST(VirtualDataPtr, Stack_Pop_Empty) {
    
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      6
          auto stack = Verbose<StackPtr>{"stack", 1};
    
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      2
          EXPECT_THROW(stack.Pop(), std::out_of_range);
    
      4
      }
    
      8
      TEST(VirtualDataPtr, Stack_Stretch) {
    
      2
          auto size = gsl::index{3};
    
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          auto stack = Verbose<StretchableStackPtr>{"stack", size};
    
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      8
          for (auto x = gsl::index{0}; x < size; x++) {
    
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      6
              stack.Push(gsl::narrow_cast<double>(x));
    
          }
    
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      2
          EXPECT_NO_THROW(stack.Push(gsl::narrow_cast<double>(size)));
    
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          EXPECT_EQ(gsl::narrow_cast<double>(size), stack.Pop());
    
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          for (auto x = size - 1; x >= 0; x--) {
    
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              EXPECT_EQ(gsl::narrow_cast<double>(x), stack.Pop());
    
          }
    
      4
      }

Line	Branch	Exec	Source
1			// See [What is “virtual data,” and how-can / why-would I use it in C++?]
2			// (https://isocpp.org/wiki/faq/value-vs-ref-semantics#virt-data)
3
4			#include "StretchableArray.hpp"
5			#include "Verbose.hpp"
6			#include "compat/gsl14.hpp"
7			#include "compat/memory14.hpp"
8
9			class StackPtr {
10			public:
11			// The base class has a normal constructor that provides its own object.
12			explicit StackPtr(gsl::index size = 1);
13
14			public:
15			void Push(double x);
16			double Pop();
17
18			protected:
19			// The base class has a constructor that accepts an object from a derived class.
20			StackPtr(std::unique_ptr<Array> data);
21
22			private:
23			// To simulate virtual data in C++, the base class has a pointer to the
24			// member object and the base class’s destructor deletes the object.
25			// Some additional memory allocation overhead is imposed.
26			std::unique_ptr<Array> data_;
27			gsl::index index_{0};
28			};
29
30			////////////////////////////////////////////////////////////////////////////////
31
32			// Virtual data makes the implementation of the derived class easier:
33			// most of the implementation is inherited.
34			class StretchableStackPtr : public StackPtr {
35			public:
36			// The derived class has a constructor that provides a new object to the base class.
37			explicit StretchableStackPtr(gsl::index size = 1);
38			};
39
40			////////////////////////////////////////////////////////////////////////////////
41
42	1/2 ✓ Branch 3 taken 3 times. ✗ Branch 4 not taken.	3	StackPtr::StackPtr(gsl::index size) : StackPtr(std::make_unique<Array>(size)) {}
43
44		8	StackPtr::StackPtr(std::unique_ptr<Array> data) : data_{std::move(data)} {}
45
46		11	void StackPtr::Push(double x) {
47		11	(*data_)[index_++] = x; // may throw
48		10	}
49
50		8	double StackPtr::Pop() {
51		8	return (*data_)[--index_]; // may throw
52			}
53
54			////////////////////////////////////////////////////////////////////////////////
55
56		1	StretchableStackPtr::StretchableStackPtr(gsl::index size) :
57	1/2 ✓ Branch 5 taken 1 times. ✗ Branch 6 not taken.	1	StackPtr{std::make_unique<StretchableArray>(size)} {}
58
59			////////////////////////////////////////////////////////////////////////////////
60
61			#include <gtest/gtest.h>
62
63		8	TEST(VirtualDataPtr, Stack_Push_Pop) {
64		2	const auto size = gsl::index{3};
65	2/4 ✓ Branch 4 taken 1 times. ✗ Branch 5 not taken. ✓ Branch 7 taken 1 times. ✗ Branch 8 not taken.	6	auto stack = Verbose<StackPtr>{"stack", size};
66	2/2 ✓ Branch 1 taken 3 times. ✓ Branch 2 taken 1 times.	8	for (auto x = gsl::index{0}; x < size; x++) {
67	1/2 ✓ Branch 2 taken 3 times. ✗ Branch 3 not taken.	6	stack.Push(gsl::narrow_cast<double>(x));
68			}
69	2/2 ✓ Branch 1 taken 3 times. ✓ Branch 2 taken 1 times.	8	for (auto x = size - 1; x >= 0; x--) {
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71			}
72		4	}
73
74		8	TEST(VirtualDataPtr, Stack_Push_Full) {
75		2	const auto size = gsl::index{3};
76	2/4 ✓ Branch 4 taken 1 times. ✗ Branch 5 not taken. ✓ Branch 7 taken 1 times. ✗ Branch 8 not taken.	6	auto stack = Verbose<StackPtr>{"stack", size};
77	2/2 ✓ Branch 1 taken 3 times. ✓ Branch 2 taken 1 times.	8	for (auto x = gsl::index{0}; x < size; x++) {
78	1/2 ✓ Branch 2 taken 3 times. ✗ Branch 3 not taken.	6	stack.Push(gsl::narrow_cast<double>(x));
79			}
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81		4	}
82
83		8	TEST(VirtualDataPtr, Stack_Pop_Empty) {
84	2/4 ✓ Branch 4 taken 1 times. ✗ Branch 5 not taken. ✓ Branch 9 taken 1 times. ✗ Branch 10 not taken.	6	auto stack = Verbose<StackPtr>{"stack", 1};
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86		4	}
87
88		8	TEST(VirtualDataPtr, Stack_Stretch) {
89		2	auto size = gsl::index{3};
90	2/4 ✓ Branch 4 taken 1 times. ✗ Branch 5 not taken. ✓ Branch 7 taken 1 times. ✗ Branch 8 not taken.	6	auto stack = Verbose<StretchableStackPtr>{"stack", size};
91	2/2 ✓ Branch 1 taken 3 times. ✓ Branch 2 taken 1 times.	8	for (auto x = gsl::index{0}; x < size; x++) {
92	1/2 ✓ Branch 2 taken 3 times. ✗ Branch 3 not taken.	6	stack.Push(gsl::narrow_cast<double>(x));
93			}
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98			}
99		4	}
100