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memory.cc
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Created
Sun, Aug 25, 21:07
Size
2 KB
Mime Type
text/x-c
Expires
Tue, Aug 27, 21:07 (1 d, 23 h)
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blob
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Raw Data
Handle
20176189
Attached To
R7571 SP4E-TB-TL-FR
memory.cc
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#include <memory>
#include <vector>
#include <iostream>
void
question1_stack
()
{
int
values
[
10
];
for
(
int
&
v
:
values
)
v
=
0
;
for
(
int
i
=
0
;
i
<
10
;
++
i
)
std
::
cout
<<
values
[
i
]
<<
" "
;
std
::
cout
<<
std
::
endl
;
}
void
question1_heap
()
{
int
*
values
=
new
int
[
10
];
// We can't use range-for with heap allocated arrays
// the best solution would use a std::vector
for
(
int
i
=
0
;
i
<
10
;
++
i
)
values
[
0
]
=
0
;
for
(
int
i
=
0
;
i
<
10
;
++
i
)
std
::
cout
<<
values
[
i
]
<<
" "
;
std
::
cout
<<
std
::
endl
;
// The memory should be deallocated, otherwise we
// have a dangling pointer
delete
[]
values
;
}
std
::
vector
<
int
>*
stack_allocation
(
int
n
)
{
std
::
vector
<
int
>
values
(
n
);
return
&
values
;
// good compilers show a warning here
}
std
::
vector
<
int
>*
heap_allocation
(
int
n
)
{
std
::
vector
<
int
>*
values
=
new
std
::
vector
<
int
>
(
n
);
return
values
;
}
void
question2
()
{
std
::
vector
<
int
>
*
stack_values
=
stack_allocation
(
10
);
std
::
vector
<
int
>
*
heap_values
=
heap_allocation
(
10
);
// stack_values->size() should fail because memory was freed
// at the end of the function stack_allocation
std
::
cout
<<
stack_values
->
size
()
<<
", "
<<
heap_values
->
size
()
<<
std
::
endl
;
// We still need to delete
delete
heap_values
;
}
void
question1_bis
()
{
std
::
array
<
int
,
10
>
stack_values
;
for
(
int
&
v
:
stack_values
)
v
=
0
;
std
::
vector
<
int
>
heap_values
(
10
);
for
(
int
&
v
:
heap_values
)
v
=
0
;
// no need to delete, everything is managed
}
std
::
unique_ptr
<
std
::
vector
<
int
>>
unique_heap_allocation
(
int
n
)
{
return
std
::
make_unique
<
std
::
vector
<
int
>>
(
n
);
}
void
question2_bis
()
{
std
::
unique_ptr
<
std
::
vector
<
int
>>
heap_vector
=
unique_heap_allocation
(
10
);
std
::
cout
<<
heap_vector
->
size
()
<<
std
::
endl
;
// no need to delete: the unique pointer will deallocate everything at
// the end of the function
}
void
question3
()
{
auto
unique
=
std
::
make_unique
<
std
::
vector
<
int
>>
(
10
);
std
::
unique_ptr
<
std
::
vector
<
int
>>
other
=
nullptr
;
// the move operation will make "unique" invalid
// so that there is ONLY ONE pointer to the resource
// hence "unique_ptr"
other
=
std
::
move
(
unique
);
// memory will be deallocated nicely by the pointer "other"
}
void
question3_bis
()
{
auto
shared
=
std
::
make_shared
<
std
::
vector
<
int
>>
(
10
);
std
::
shared_ptr
<
std
::
vector
<
int
>>
other
=
nullptr
;
// This works because they are shared pointer
other
=
shared
;
// memory will be deallocated nicely
}
int
main
()
{
question1_stack
();
question1_heap
();
//question2(); <-- this causes an error
question1_bis
();
question2_bis
();
question3
();
question3_bis
();
return
0
;
}
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