logo
Tags down

shadow

C++ temporary variable lifetime?


By : Alanpasi
Date : September 16 2020, 05:00 PM
hop of those help? The temporary std::string inside of f2 is destroyed when the function returns. The char* will be dangling.
EDIT: In response to the comment, std::string x = f2() is also not valid. It's still bad to initialize a std::string from a dangling pointer.
code :


Share : facebook icon twitter icon

Why lifetime of temporary doesn't extend till lifetime of enclosing object?


By : viki
Date : March 29 2020, 07:55 AM
Does that help The standard considers two circumstances under which the lifetime of a temporary is extended:
code :
B* f() {
   B * bp = new B(A());
   return b;
}
void test() {
   B* p = f();
   delete p;
}

C++ temporary variable lifetime


By : chocokiko chocokiko
Date : March 29 2020, 07:55 AM
will be helpful for those in need The code you've shown is illegal – temporaries can only bind to rvalue references or const lvalue references.
VC++ happens to allow it as an extension (and gives a level 4 warning saying so).

C++ variable lifetime -- need workaround to return temporary


By : carlosls
Date : March 29 2020, 07:55 AM
I wish did fix the issue. The most obvious solution is to define a type which contains the std::string, and converts implicitly to a char const*. Something like:
code :
class ToPlainC
{
    std::string myValue
public:
    ToPlainC( boost::format const& fmt )
        : myValue( fmt.str() )
    {
    }
    operator char const*() const
    {
        return myValue.c_str();
    }
};
lib_function( ToPlainC( boost::format( "%1% %2%" ) % "1" % "2" ) );

Rust temporary variable lifetime in method chaining


By : Rubbish001
Date : March 29 2020, 07:55 AM
it fixes the issue An if let construct is just syntactic sugar for a match construct. let Some(B(v @ 0...4)) = a(4).get_b() is not a conditional used in a regular if expression, because it is not an expression that evaluates to bool. Given your example:
code :
if let Some(B(v @ 0...4)) = a(4).get_b() {
    println!("some {}", v);
}
match a(4).get_b() {
    Some(B(v @ 0...4)) => {
        println!("some {}", v);
    }
    _ => {}
}

How can I extend the lifetime of a temporary variable inside of an iterator adaptor in Rust?


By : user2899291
Date : March 29 2020, 07:55 AM
To fix the issue you can do I have a method make_iter() which creates an Iterator with multiple adapters in Rust, which can be simplified as the following MCVE: ,
extend the lifetime of this object
code :
use std::iter;

fn example(outer: impl Iterator<Item = Inner>) {
    outer.flat_map(|i| i.iter().map(|v| v.clone()));
}

struct Inner;

impl Inner {
    fn iter(&self) -> impl Iterator<Item = &()> + '_ {
        iter::empty()
    }
}
fn example(outer: impl Iterator<Item = Inner>) {
    outer.flat_map(|i| i.iter().map(|v| v.clone()).collect::<Vec<_>>());
}
use std::iter;

fn example(outer: impl Iterator<Item = Inner>) {
    outer.flat_map(|i| i.into_iter().map(|v| v));
}

struct Inner;

impl Inner {
    fn into_iter(self) -> impl Iterator<Item = ()> {
        iter::empty()
    }
}
Related Posts Related Posts :
  • Short Parameter Type in C++
  • Build a compile time command look up table using template metaprogramming
  • Explicitly calling a destructor when you only have a shared_ptr to the base class?
  • How do compilers know C++ constexpr computations do not trigger undefined behavior?
  • Adding a Node in a Singly linked lists (supports adding in front, end and middle)
  • What should I use to read integers from a file
  • Is any use of a union clearly well defined, in any revision of C++?
  • Is it possible to create iterators with C++14 that are C++17 compliant?
  • Is it crucial to know by which compiler a specific binary generated in C++?
  • Mixing separately compiled objects
  • Sort unique values from a map<string, vector<string>>
  • How does shared_ptr work in c++ without initialization
  • visual C++ professional
  • What is the best way to pass uint8_t* buffer and size_t bufferlen to API function in C from a C++
  • Writing a function for arranging the elements in an array
  • C++ Linked List Node Refers to Itself
  • Limit variable template to a list of types
  • How can I use the function std::min() to calculate the minimum?
  • How to return a value from a constant array in a single line in C++
  • How to use QtCreator instead of gdb to debug C++ code in an R package based on Rcpp
  • How to elide copy when chaining?
  • Why c++ use throw() keyword to indicate the function won't throw any exceptions
  • specifying arguments to the compare function in C++ sort
  • How to ignore specific bits in a 32-bit integer
  • Prevent gcc from mangling my AVX2 intrinsics copy into REP MOVS
  • Is it possible to make a function return a typename in C++?
  • getline method only working once in nested loop
  • Is it ok to return default argument's value by const reference?
  • function with variable number of arguments that are converted to a string
  • if (static_cast<bool>(x)) vs if (x)
  • Mapping from a size to the corresponding uintN_t type
  • C++ to Assembly
  • How to check answers through an answer set using c++?
  • What does the address of a vector represent?
  • Polymorphic member class for non-virtual base
  • Arduino shows odd behaviour with LED output in loop
  • C++20 std::atomic<float>- std::atomic<double>.specializations
  • reading variable length input in C++ using stream
  • Why does a memory leak occur in this code when a bad_alloc exception is thrown for T2
  • Passing an object as a parameter in C++
  • why we using arrow and dot opertor only for user defined data types why not for primitive data types?
  • identifier "in" is undefined
  • Is there a tool to identify what external identifiers a set of C++ source files refer to?
  • Overloading << for both iostream and fstream
  • Zero cost abstraction for executing same statement on multiple objects
  • Const reference to temporary object does not extend its lifetime
  • Extracting decimal points in C++
  • Unable to get output for multiplication
  • no matching operator delete found; memory will not be freed if initialization throws an exception
  • Connect a UDP socket, but still receive datagrams from other sources
  • How to access elements of vector of pairs using a pointer?
  • Class is not a template error when converting code from non-template to templates
  • Detect that text number is too large to convert to Int in swift
  • Does Vulkan already have multi-threading by default?
  • Why does use of delete cause core dump?
  • Issue with memory leak
  • What's the exact maximum value of `long long int` in C++?
  • Problems with making vector function from the existing code C++
  • C++: how to define class instance in structure. Class has parametrized constructor
  • Copy constructor of vector<vector> c++
  • shadow
    Privacy Policy - Terms - Contact Us © 35dp-dentalpractice.co.uk