Compilation failure with constexpr if

[bernhardmgruber]

Hi! I did not find a better way to report this issue, so I report it here:

Using icpc (ICC) 2021.1.2 20201208 via oneAPI on Ubuntu 20.10 fails to compile the following program:

#include <fstream>

constexpr auto FALSE = false;

template <typename T>
void f() {
    if constexpr (FALSE)
        std::ofstream{"file"} << "asdf";
}

int main() {
    f<int>();
}

<source>(8): error: expected an expression
          std::ofstream{"file"} << "asdf";
                                ^
          detected during instantiation of "void f<T>() [with T=int]" at line 13

Godbolt: https://godbolt.org/z/7vb1ah6av

The problem does not appear if `f` is not a template, if `FALSE` is `true`, or the ctor of the temporary `ostream` is called using parentheses. I think this is a frontend issue parsing the body of the constexpr if.

I have a more complex case of this happending in my library, so I would be happy if the compiler team could address this. Thank you!

[AbhishekD_Intel]

Hi,

Thanks for the complete details and the reproducer.

We are also getting the same error with the ICC Compiler(2021.1.2 20201208), and those errors are very much reproducible. We will look into this issue.

Meanwhile, you can use the ICX Compiler to compile your use-case.

Warm Regards,

Abhishek

[Viet_H_Intel]

I've reported this bug to our Front End team.

Thanks,

[VidyalathaB_Intel]

Hi,

The version against which you reported your issue is no longer targeted for fixes. Please check out the new versions of Intel oneAPI Toolkits for the latest features.

Regards,

Vidya.

.

[VidyalathaB_Intel]

Hi,

We are closing this thread for now. If you need any additional information, please post a new question as this thread will no longer be monitored by Intel.

Thanks & Regards,

Vidya.