* GCC Bug (tried to create an account)
@ 2017-01-18 12:21 Scala Hater
0 siblings, 0 replies; only message in thread
From: Scala Hater @ 2017-01-18 12:21 UTC (permalink / raw)
To: overseers
Hello, I send an email to you because I tried to create an account in order to
file a bug.
Given the following code:
> #include <iostream>
>
> int a = 12;
>
> int main()
> {
>
> auto lambda = [&](int i) -> void {
>
> std::cout << a << " " << i << std::endl;
> a = i;
> std::cout << a << std::endl;
>
> };
> void (*f)(int) = lambda; // This should explode in your face
> f(5);
> std::cout << a << std::endl;
> return 0;
>
> }
In the line:
> void (*f)(int) = lambda;
We are assigning a lambda to a function pointer. According to the
documentation here: http://en.cppreference.com/w/cpp/language/lambda It is
stated that:
>This user-defined conversion function is only defined if the capture list of
the lambda-expression is empty
This should give an error whenever the lambda is declared with a capture list.
On other compilers like Clang, MSVC, etc... when lambdas are declared with a
capture list and this exact same situation, compilation fails. In GCC it only
fails when a variable is actually captured (by using it inside the lambda).
See the following links for comparison:
gcc: http://cpp.sh/9tphj
clang: https://godbolt.org/g/N88pbH
Please note that in the example the variable a is global, so even without a
capture, this variable can be used inside the function. On the other hand when
a is a local variable, compilation correctly fails.
Thanks.
Marc & Adrià from Catalonia.
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