Use the do {} while (false) idiom for BOOST_TEST_THROWS() and BOOST_TEST_NO_THROW()

[gennaroprota]

Reason: Common hygiene for multi-line macros. Makes things like

if (condition)
    BOOST_TEST_THROWS(...);
else
    ...

work correctly. Also, it doesn't generate an empty statement (which compilers may warn about) when the user adds a semicolon (which they usually do).

[pdimov]

This is technically a breaking change because the semicolon is now required, whereas it wasn't before. But it looks like all our uses have a semicolon.

The backslash at the last line shouldn't be present. We should remove it from BOOST_TEST_THROWS, instead of adding it to BOOST_TEST_NO_THROW.

[gennaroprota]

The backslash at the last line shouldn't be present. We should remove it from BOOST_TEST_THROWS, instead of adding it to BOOST_TEST_NO_THROW.

I thought the convention was to terminate with a // comment:

last_line    \
//

Didn't notice this hadn't been done for BOOST_TEST_NO_THROW().

[pdimov]

libs\core\test\lightweight_test_test.cpp(105) : warning C4127: conditional expression is constant

Yeah :-/

[gennaroprota]

Sigh. Which version of MSVC? I don't get that warning with MSVC 2022 and /Wall.

[pdimov]

Up to msvc-12.0 according to Appveyor.

[gennaroprota]

Hmm. We might try with do {} while (0), which is probably more common and might be special-cased, even in old versions of MSVC.

[Lastique]

Just add _Pragma("warning(disable: 4127)") to the macros. With the corresponding push and pop pragmas as well.

[pdimov]

BOOST_TEST_xxx is a public macro name. Please use BOOST_LWT_DETAIL_xxx for implementation details.

[Lastique]

One other alternative we could try is for (;;) { x; break; }.

[gennaroprota]

That doesn't play well with the semicolon (the one after the macro invocation).

[Lastique]

Minor nit: better spell the second comparison as BOOST_MSVC >= x, where x is the oldest version we know works. This saves from some SP or Update with a version that is higher than 1900 but still issues the warning.

[pdimov]

1900 looks wrong, 1900 is msvc 14.0 unpatched. Should be >= 1900.

[gennaroprota]

Note that I test if the compiler is not MSVC or is MSVC > 2015. I think 2015 still emits the warning for do {} while (false) (while MSVC 2017 doesn't), right? I might change the second test to >= 1910 though, as Lastique suggested.

MSVC 2015 == 1900
MSVC 2017 == 1910

[pdimov]

No, msvc-14.0 doesn't emit the warning. But if it did, >= 1910 would be the correct check.

[gennaroprota]

Oh, sorry. Too many irons in the fire :-). Fixed, now.

[pdimov]

Everything fails, probably because you're missing a semicolon here BOOST_LWT_DETAIL_DO_WHILE_FALSE(static_cast<void>(0)).

[pdimov]

(void)0; is probably a more idiomatic form of a null statement, despite the C cast.

[gennaroprota]

Do you prefer that? (Why?)

[pdimov]

It's idiomatic because that's what assert typically uses.

Nowadays (void) is also emerging as the idiomatic way to silence nodiscard warnings.

[gennaroprota]

I don't have a strong opinion about that. I can change it, if you like. (About assert(), though, I think it's (void) because it's common to C.)

[pdimov]

Yes please, let's go with (void). I've always found static_cast<void> somewhat pretentious, and it does require parentheses around the expression which is also a bit jarring.