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range-v3: strange Behavior

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1

1

I am trying to play with range-v3 and I encountered a problems : it does not extract values from a vector as I would have wanted.

See the code below:

1. When running, it outputs (0, 0), instead of what I would have thought, i.e (1, 0)




2. If I uncomment the line auto pairs = ..., then the result is changed, and the output becomes (33144464,0), although the variable pairs is unused (and the assert will fail)

#include <iostream>
#include <vector>
#include <range/v3/all.hpp>

auto foo()

 auto values = std::vector<int> 1, 0 ;
 // auto pairs = std::vector< std::pair<int, int> > 1, 0 , 0, 1 , 0, 0 ;

 return ranges::view::for_each(values, [=](int nb)
 );



int main()

 ranges::for_each(foo(), [](auto v) 
 std::cout << v << "n";
 );

This code was compiled with g++ (g++ (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0) and clang++ (clang version 8.0.0 (tags/RELEASE_800/final)) with the following commands:

g++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic
clang++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic

I am using a fresh clone for ranges-v3, and I can reproduce this on ubuntu and OSX (with AppleClang).

c++ range-v3

share|improve this question

edited Mar 22 at 22:18

Pascal T.

asked Mar 22 at 22:13

Pascal T.Pascal T.

2,01332529

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  I suspect it’s because values has ceased to exist by the time you try to access it through the view.
  
  – molbdnilo
  Mar 22 at 22:25
  

  
  
  
  

add a comment | 

1

1

I am trying to play with range-v3 and I encountered a problems : it does not extract values from a vector as I would have wanted.

See the code below:

1. When running, it outputs (0, 0), instead of what I would have thought, i.e (1, 0)




2. If I uncomment the line auto pairs = ..., then the result is changed, and the output becomes (33144464,0), although the variable pairs is unused (and the assert will fail)

#include <iostream>
#include <vector>
#include <range/v3/all.hpp>

auto foo()

 auto values = std::vector<int> 1, 0 ;
 // auto pairs = std::vector< std::pair<int, int> > 1, 0 , 0, 1 , 0, 0 ;

 return ranges::view::for_each(values, [=](int nb)
 );



int main()

 ranges::for_each(foo(), [](auto v) 
 std::cout << v << "n";
 );

This code was compiled with g++ (g++ (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0) and clang++ (clang version 8.0.0 (tags/RELEASE_800/final)) with the following commands:

g++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic
clang++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic

I am using a fresh clone for ranges-v3, and I can reproduce this on ubuntu and OSX (with AppleClang).

c++ range-v3

share|improve this question

edited Mar 22 at 22:18

Pascal T.

asked Mar 22 at 22:13

Pascal T.Pascal T.

2,01332529

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  I suspect it’s because values has ceased to exist by the time you try to access it through the view.
  
  – molbdnilo
  Mar 22 at 22:25
  

  
  
  
  

add a comment | 

I am trying to play with range-v3 and I encountered a problems : it does not extract values from a vector as I would have wanted.

See the code below:

1. When running, it outputs (0, 0), instead of what I would have thought, i.e (1, 0)




2. If I uncomment the line auto pairs = ..., then the result is changed, and the output becomes (33144464,0), although the variable pairs is unused (and the assert will fail)

#include <iostream>
#include <vector>
#include <range/v3/all.hpp>

auto foo()

 auto values = std::vector<int> 1, 0 ;
 // auto pairs = std::vector< std::pair<int, int> > 1, 0 , 0, 1 , 0, 0 ;

 return ranges::view::for_each(values, [=](int nb)
 );



int main()

 ranges::for_each(foo(), [](auto v) 
 std::cout << v << "n";
 );

This code was compiled with g++ (g++ (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0) and clang++ (clang version 8.0.0 (tags/RELEASE_800/final)) with the following commands:

g++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic
clang++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic

I am using a fresh clone for ranges-v3, and I can reproduce this on ubuntu and OSX (with AppleClang).

c++ range-v3

share|improve this question

edited Mar 22 at 22:18

Pascal T.

asked Mar 22 at 22:13

Pascal T.Pascal T.

2,01332529

#include <iostream>
#include <vector>
#include <range/v3/all.hpp>

auto foo()

 auto values = std::vector<int> 1, 0 ;
 // auto pairs = std::vector< std::pair<int, int> > 1, 0 , 0, 1 , 0, 0 ;

 return ranges::view::for_each(values, [=](int nb)
 );



int main()

 ranges::for_each(foo(), [](auto v) 
 std::cout << v << "n";
 );

g++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic
clang++ foo.cpp -std=c++14 -Irange-v3/include -Wall -Wpedantic

share|improve this question

edited Mar 22 at 22:18

Pascal T.

asked Mar 22 at 22:13

Pascal T.Pascal T.

2,01332529

share|improve this question

edited Mar 22 at 22:18

Pascal T.

asked Mar 22 at 22:13

Pascal T.Pascal T.

2,01332529

asked Mar 22 at 22:13

Pascal T.Pascal T.

2,01332529

asked Mar 22 at 22:13

Pascal T.Pascal T.

2,01332529

1 Answer
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There is a experimental feature coming in clang called -Wlifetime that can be used on godbolt. It gives the following warnings pointing to the return from foo.

[x86-64 clang (experimental -Wlifetime) #1] warning: returning a dangling Pointer [-Wlifetime]
[x86-64 clang (experimental -Wlifetime) #1] note: pointee 'values' left the scope here

share|improve this answer

answered Mar 24 at 15:36

sv90sv90

30339

add a comment | 

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0

There is a experimental feature coming in clang called -Wlifetime that can be used on godbolt. It gives the following warnings pointing to the return from foo.

[x86-64 clang (experimental -Wlifetime) #1] warning: returning a dangling Pointer [-Wlifetime]
[x86-64 clang (experimental -Wlifetime) #1] note: pointee 'values' left the scope here

share|improve this answer

answered Mar 24 at 15:36

sv90sv90

30339

add a comment | 

0

There is a experimental feature coming in clang called -Wlifetime that can be used on godbolt. It gives the following warnings pointing to the return from foo.

[x86-64 clang (experimental -Wlifetime) #1] warning: returning a dangling Pointer [-Wlifetime]
[x86-64 clang (experimental -Wlifetime) #1] note: pointee 'values' left the scope here

share|improve this answer

answered Mar 24 at 15:36

sv90sv90

30339

add a comment | 

There is a experimental feature coming in clang called -Wlifetime that can be used on godbolt. It gives the following warnings pointing to the return from foo.

[x86-64 clang (experimental -Wlifetime) #1] warning: returning a dangling Pointer [-Wlifetime]
[x86-64 clang (experimental -Wlifetime) #1] note: pointee 'values' left the scope here

share|improve this answer

answered Mar 24 at 15:36

sv90sv90

30339

[x86-64 clang (experimental -Wlifetime) #1] warning: returning a dangling Pointer [-Wlifetime]
[x86-64 clang (experimental -Wlifetime) #1] note: pointee 'values' left the scope here

share|improve this answer

answered Mar 24 at 15:36

sv90sv90

30339

answered Mar 24 at 15:36

sv90sv90

30339

answered Mar 24 at 15:36

sv90sv90

30339