Initialise a reference member to C array don't compile on visual studio 2015
When I try to compile the code below on g++ it's work but on vs2015 it's fail with message :
error C2440: 'initializing': cannot convert from 'const bool *' to 'const bool (&)[3]'
#include <iostream>
enum class Direction
{
RIGTH,
LEFT
};
struct Buffer
{
int catRigth = 4;
int catLeft = 8;
bool dogRigth[3] = {true, false, true};
bool dogLeft[3] = {false, true, false};
};
struct Bind
{
const int &cat;
const bool (&dog)[3];
Bind(const Buffer &buf, Direction direction) :
cat(direction == Direction::RIGTH ? buf.catRigth : buf.catLeft),
dog(direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)
{
}
};
int main(int argc, char* argv)
{
const Buffer buff;
Bind bindRigth(buff, Direction::RIGTH);
Bind bindLeft(buff, Direction::LEFT);
int catRigth = bindRigth.cat;
int catLeft = bindLeft.cat;
std::cout << catRigth << " " << catLeft;
}
Is it a standard C++ code or it's gcc specific comportment?
c++ visual-studio-2015
asked Nov 23 '18 at 10:33
GurdilGurdil
186
|
show 4 more comments
When I try to compile the code below on g++ it's work but on vs2015 it's fail with message :
error C2440: 'initializing': cannot convert from 'const bool *' to 'const bool (&)[3]'
#include <iostream>
enum class Direction
{
RIGTH,
LEFT
};
struct Buffer
{
int catRigth = 4;
int catLeft = 8;
bool dogRigth[3] = {true, false, true};
bool dogLeft[3] = {false, true, false};
};
struct Bind
{
const int &cat;
const bool (&dog)[3];
Bind(const Buffer &buf, Direction direction) :
cat(direction == Direction::RIGTH ? buf.catRigth : buf.catLeft),
dog(direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)
{
}
};
int main(int argc, char* argv)
{
const Buffer buff;
Bind bindRigth(buff, Direction::RIGTH);
Bind bindLeft(buff, Direction::LEFT);
int catRigth = bindRigth.cat;
int catLeft = bindLeft.cat;
std::cout << catRigth << " " << catLeft;
}
Is it a standard C++ code or it's gcc specific comportment?
c++ visual-studio-2015
asked Nov 23 '18 at 10:33
GurdilGurdil
186
Or in other words: does the conditional operator trigger array-to-pointer decay?
– Quentin
Nov 23 '18 at 10:38
Seems like only MSVC has this behavior. clang, gcc and icc work as "expected"
– Matthieu Brucher
Nov 23 '18 at 10:39
Initialize it like this: _dog { direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)} {}
– snake_style
Nov 23 '18 at 11:03
Tried your code out on cpp.sh, it complained about obj not being initialized. Did that, worked then. Maybe doing that makes it work on vs2015 too? (Altered code: cpp.sh/3wqyg ) In any case ugly code, why don't you simply use a pointer?
– Aziuth
Nov 23 '18 at 11:39
Sorry I accepted the edit by Felix when I probably don't do, I'm new here. I tested my code on real vs and it don't compiled.
– Gurdil
Nov 23 '18 at 11:57
|
show 4 more comments
When I try to compile the code below on g++ it's work but on vs2015 it's fail with message :
error C2440: 'initializing': cannot convert from 'const bool *' to 'const bool (&)[3]'
#include <iostream>
enum class Direction
{
RIGTH,
LEFT
};
struct Buffer
{
int catRigth = 4;
int catLeft = 8;
bool dogRigth[3] = {true, false, true};
bool dogLeft[3] = {false, true, false};
};
struct Bind
{
const int &cat;
const bool (&dog)[3];
Bind(const Buffer &buf, Direction direction) :
cat(direction == Direction::RIGTH ? buf.catRigth : buf.catLeft),
dog(direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)
{
}
};
int main(int argc, char* argv)
{
const Buffer buff;
Bind bindRigth(buff, Direction::RIGTH);
Bind bindLeft(buff, Direction::LEFT);
int catRigth = bindRigth.cat;
int catLeft = bindLeft.cat;
std::cout << catRigth << " " << catLeft;
}
Is it a standard C++ code or it's gcc specific comportment?
c++ visual-studio-2015
asked Nov 23 '18 at 10:33
GurdilGurdil
186
When I try to compile the code below on g++ it's work but on vs2015 it's fail with message :
error C2440: 'initializing': cannot convert from 'const bool *' to 'const bool (&)[3]'
#include <iostream>
enum class Direction
{
RIGTH,
LEFT
};
struct Buffer
{
int catRigth = 4;
int catLeft = 8;
bool dogRigth[3] = {true, false, true};
bool dogLeft[3] = {false, true, false};
};
struct Bind
{
const int &cat;
const bool (&dog)[3];
Bind(const Buffer &buf, Direction direction) :
cat(direction == Direction::RIGTH ? buf.catRigth : buf.catLeft),
dog(direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)
{
}
};
int main(int argc, char* argv)
{
const Buffer buff;
Bind bindRigth(buff, Direction::RIGTH);
Bind bindLeft(buff, Direction::LEFT);
int catRigth = bindRigth.cat;
int catLeft = bindLeft.cat;
std::cout << catRigth << " " << catLeft;
}
Is it a standard C++ code or it's gcc specific comportment?
c++ visual-studio-2015
c++ visual-studio-2015
asked Nov 23 '18 at 10:33
GurdilGurdil
186
asked Nov 23 '18 at 10:33
GurdilGurdil
186
edited Nov 23 '18 at 12:23
Gurdil
asked Nov 23 '18 at 10:33
GurdilGurdil
186
asked Nov 23 '18 at 10:33
GurdilGurdil
186
asked Nov 23 '18 at 10:33
GurdilGurdil
186
186
Or in other words: does the conditional operator trigger array-to-pointer decay?
– Quentin
Nov 23 '18 at 10:38
Seems like only MSVC has this behavior. clang, gcc and icc work as "expected"
– Matthieu Brucher
Nov 23 '18 at 10:39
Initialize it like this: _dog { direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)} {}
– snake_style
Nov 23 '18 at 11:03
Tried your code out on cpp.sh, it complained about obj not being initialized. Did that, worked then. Maybe doing that makes it work on vs2015 too? (Altered code: cpp.sh/3wqyg ) In any case ugly code, why don't you simply use a pointer?
– Aziuth
Nov 23 '18 at 11:39
Sorry I accepted the edit by Felix when I probably don't do, I'm new here. I tested my code on real vs and it don't compiled.
– Gurdil
Nov 23 '18 at 11:57
|
show 4 more comments
Or in other words: does the conditional operator trigger array-to-pointer decay?
– Quentin
Nov 23 '18 at 10:38
Seems like only MSVC has this behavior. clang, gcc and icc work as "expected"
– Matthieu Brucher
Nov 23 '18 at 10:39
Initialize it like this: _dog { direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)} {}
– snake_style
Nov 23 '18 at 11:03
Tried your code out on cpp.sh, it complained about obj not being initialized. Did that, worked then. Maybe doing that makes it work on vs2015 too? (Altered code: cpp.sh/3wqyg ) In any case ugly code, why don't you simply use a pointer?
– Aziuth
Nov 23 '18 at 11:39
Sorry I accepted the edit by Felix when I probably don't do, I'm new here. I tested my code on real vs and it don't compiled.
– Gurdil
Nov 23 '18 at 11:57
Or in other words: does the conditional operator trigger array-to-pointer decay?
– Quentin
Nov 23 '18 at 10:38
Or in other words: does the conditional operator trigger array-to-pointer decay?
– Quentin
Nov 23 '18 at 10:38
Seems like only MSVC has this behavior. clang, gcc and icc work as "expected"
– Matthieu Brucher
Nov 23 '18 at 10:39
Seems like only MSVC has this behavior. clang, gcc and icc work as "expected"
– Matthieu Brucher
Nov 23 '18 at 10:39
Initialize it like this: _dog { direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)} {}
– snake_style
Nov 23 '18 at 11:03
Initialize it like this: _dog { direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)} {}
– snake_style
Nov 23 '18 at 11:03
Tried your code out on cpp.sh, it complained about obj not being initialized. Did that, worked then. Maybe doing that makes it work on vs2015 too? (Altered code: cpp.sh/3wqyg ) In any case ugly code, why don't you simply use a pointer?
– Aziuth
Nov 23 '18 at 11:39
Tried your code out on cpp.sh, it complained about obj not being initialized. Did that, worked then. Maybe doing that makes it work on vs2015 too? (Altered code: cpp.sh/3wqyg ) In any case ugly code, why don't you simply use a pointer?
– Aziuth
Nov 23 '18 at 11:39
Sorry I accepted the edit by Felix when I probably don't do, I'm new here. I tested my code on real vs and it don't compiled.
– Gurdil
Nov 23 '18 at 11:57
Sorry I accepted the edit by Felix when I probably don't do, I'm new here. I tested my code on real vs and it don't compiled.
– Gurdil
Nov 23 '18 at 11:57
|
show 4 more comments
1 Answer
1
active
oldest
votes
MSVC shouldn't have decayed its type to const bool *:
5.16.4 If the second and third operands are glvalues of the same value category and have the same type, the result is of that type and value category and it is a bit-field if the second or the third operand is a bit-field, or if both are bit-fields.
A workaround for MSVC could be:
#include <utility>
const struct A {
bool a[3] = {false};
} obj;
template <class Lhs, class Rhs>
auto &&Conditional(const bool x, Lhs &&lhs, Rhs &&rhs) {
if (x)
return std::forward<Lhs>(lhs);
return std::forward<Rhs>(rhs);
}
int main(int argc, char* argv) {
const bool (&t)[3] = Conditional(true, obj.a, obj.a);
return 0;
}
PS: Conditional isn't a constexpr function.
Or: const bool (&t)[3] = *(true ? &obj.a : &obj.a);
answered Nov 23 '18 at 12:38
felixfelix
1,510314
Thanks your solution to reference on ternary and dereference the result do the job for me
– Gurdil
Nov 23 '18 at 13:01
add a comment |
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1 Answer
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1 Answer
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oldest
votes
MSVC shouldn't have decayed its type to const bool *:
5.16.4 If the second and third operands are glvalues of the same value category and have the same type, the result is of that type and value category and it is a bit-field if the second or the third operand is a bit-field, or if both are bit-fields.
A workaround for MSVC could be:
#include <utility>
const struct A {
bool a[3] = {false};
} obj;
template <class Lhs, class Rhs>
auto &&Conditional(const bool x, Lhs &&lhs, Rhs &&rhs) {
if (x)
return std::forward<Lhs>(lhs);
return std::forward<Rhs>(rhs);
}
int main(int argc, char* argv) {
const bool (&t)[3] = Conditional(true, obj.a, obj.a);
return 0;
}
PS: Conditional isn't a constexpr function.
Or: const bool (&t)[3] = *(true ? &obj.a : &obj.a);
answered Nov 23 '18 at 12:38
felixfelix
1,510314
Thanks your solution to reference on ternary and dereference the result do the job for me
– Gurdil
Nov 23 '18 at 13:01
add a comment |
MSVC shouldn't have decayed its type to const bool *:
5.16.4 If the second and third operands are glvalues of the same value category and have the same type, the result is of that type and value category and it is a bit-field if the second or the third operand is a bit-field, or if both are bit-fields.
A workaround for MSVC could be:
#include <utility>
const struct A {
bool a[3] = {false};
} obj;
template <class Lhs, class Rhs>
auto &&Conditional(const bool x, Lhs &&lhs, Rhs &&rhs) {
if (x)
return std::forward<Lhs>(lhs);
return std::forward<Rhs>(rhs);
}
int main(int argc, char* argv) {
const bool (&t)[3] = Conditional(true, obj.a, obj.a);
return 0;
}
PS: Conditional isn't a constexpr function.
Or: const bool (&t)[3] = *(true ? &obj.a : &obj.a);
answered Nov 23 '18 at 12:38
felixfelix
1,510314
Thanks your solution to reference on ternary and dereference the result do the job for me
– Gurdil
Nov 23 '18 at 13:01
add a comment |
MSVC shouldn't have decayed its type to const bool *:
5.16.4 If the second and third operands are glvalues of the same value category and have the same type, the result is of that type and value category and it is a bit-field if the second or the third operand is a bit-field, or if both are bit-fields.
A workaround for MSVC could be:
#include <utility>
const struct A {
bool a[3] = {false};
} obj;
template <class Lhs, class Rhs>
auto &&Conditional(const bool x, Lhs &&lhs, Rhs &&rhs) {
if (x)
return std::forward<Lhs>(lhs);
return std::forward<Rhs>(rhs);
}
int main(int argc, char* argv) {
const bool (&t)[3] = Conditional(true, obj.a, obj.a);
return 0;
}
PS: Conditional isn't a constexpr function.
Or: const bool (&t)[3] = *(true ? &obj.a : &obj.a);
answered Nov 23 '18 at 12:38
felixfelix
1,510314
MSVC shouldn't have decayed its type to const bool *:
5.16.4 If the second and third operands are glvalues of the same value category and have the same type, the result is of that type and value category and it is a bit-field if the second or the third operand is a bit-field, or if both are bit-fields.
A workaround for MSVC could be:
#include <utility>
const struct A {
bool a[3] = {false};
} obj;
template <class Lhs, class Rhs>
auto &&Conditional(const bool x, Lhs &&lhs, Rhs &&rhs) {
if (x)
return std::forward<Lhs>(lhs);
return std::forward<Rhs>(rhs);
}
int main(int argc, char* argv) {
const bool (&t)[3] = Conditional(true, obj.a, obj.a);
return 0;
}
PS: Conditional isn't a constexpr function.
Or: const bool (&t)[3] = *(true ? &obj.a : &obj.a);
answered Nov 23 '18 at 12:38
felixfelix
1,510314
edited Nov 23 '18 at 12:56
answered Nov 23 '18 at 12:38
felixfelix
1,510314
answered Nov 23 '18 at 12:38
felixfelix
1,510314
answered Nov 23 '18 at 12:38
felixfelix
1,510314
1,510314
Thanks your solution to reference on ternary and dereference the result do the job for me
– Gurdil
Nov 23 '18 at 13:01
add a comment |
Thanks your solution to reference on ternary and dereference the result do the job for me
– Gurdil
Nov 23 '18 at 13:01
Thanks your solution to reference on ternary and dereference the result do the job for me
– Gurdil
Nov 23 '18 at 13:01
Thanks your solution to reference on ternary and dereference the result do the job for me
– Gurdil
Nov 23 '18 at 13:01
add a comment |
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Or in other words: does the conditional operator trigger array-to-pointer decay?
– Quentin
Nov 23 '18 at 10:38
Seems like only MSVC has this behavior. clang, gcc and icc work as "expected"
– Matthieu Brucher
Nov 23 '18 at 10:39
Initialize it like this: _dog { direction == Direction::RIGTH ? buf.dogRigth : buf.dogLeft)} {}
– snake_style
Nov 23 '18 at 11:03
Tried your code out on cpp.sh, it complained about obj not being initialized. Did that, worked then. Maybe doing that makes it work on vs2015 too? (Altered code: cpp.sh/3wqyg ) In any case ugly code, why don't you simply use a pointer?
– Aziuth
Nov 23 '18 at 11:39
Sorry I accepted the edit by Felix when I probably don't do, I'm new here. I tested my code on real vs and it don't compiled.
– Gurdil
Nov 23 '18 at 11:57