Our website uses cookies to enhance your browsing experience.
Accept
to the top
>
>
>
V788. Review captured variable in...
menu mobile close menu
Additional information
toggle menu Contents

V788. Review captured variable in lambda expression.

May 23 2017

The analyzer detected a suspicious variable capture in a lambda function.

Consider a few examples of this diagnostic.

Example 1:

int x = 0;
auto f = [x] { };
....
x = 42;
f();
...

A variable whose exact value can be calculated at compile time is captured by value in a lambda function. Inside that function, the variable will be referring to the value that it had at the moment when it was captured rather than at the moment when the function call was executed. The variable should probably be captured by reference instead.

int x = 0;
auto f = [&x] { };
....
x = 42;
f();
...

Another possible explanation is that the code where the variable used to be assigned some value was removed during refactoring.

int x = 0;
if (condition) x = 42;
else x = 43;
auto f = [x] { };

If you need to capture a constant, a better solution would be to explicitly declare the variable's type as 'const' or 'constexpr'.

constexpr int x = 0;
auto f = [x] { };

Example 2:

int x;
auto f = [x] { };

An uninitialized variable is captured by value. Using it will lead to undefined behavior. If the variable was meant to be initialized by the function call, then it should be captured by reference.

int x;
auto f = [&x] { x = 42; };

This diagnostic is classified as:

close form

Fill out the form in 2 simple steps below:

Your contact information:

Step 1
Congratulations! This is your promo code!

Desired license type:

Step 2
Team license
Enterprise license
close form
Request our prices
New License
License Renewal
--Select currency--
USD
EUR
close form
Free PVS‑Studio license for Microsoft MVP specialists
close form
To get the licence for your open-source project, please fill out this form
close form
I want to join the test
* By clicking this button you agree to our Privacy Policy statement

close form
check circle
Message submitted.

Your message has been sent. We will email you at


If you do not see the email in your inbox, please check if it is filtered to one of the following folders:

  • Promotion
  • Updates
  • Spam