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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 :

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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
    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 = &()> + '_ {
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 = ()> {
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