Re: [Boost-users] [Boost][Test] Compile error with BOOST_REQUIRE_THROW

Subject: Re: [Boost-users] [Boost][Test] Compile error with BOOST_REQUIRE_THROW
From: Richard (legalize+jeeves_at_[hidden])
Date: 2011-08-28 13:06:00

[Please do not mail me a copy of your followup]

boost-users_at_[hidden] spake the secret code
<4E583EC5.7080700_at_[hidden]> thusly:

>I've just found that we have a compiler error when using the 
>BOOST_REQUIRE_THROW macro in a if/else statement with implicit block. 
>Let's have an example:
>
>BOOST_AUTO_TEST_CASE(foo)
>{
>     if(true)
>         BOOST_REQUIRE_THROW(throw std::exception(), std::exception);
>     else
>         BOOST_REQUIRE_THROW(throw std::exception(), std::exception);
>}
>
>Will fail with:
>
>file.cpp: In member function ‘void foo::test_method()’:
>file.cpp:184:2: error: ‘else’ without a previous ‘if’

BOOST_REQUIRE_THROW expands into a try { ... } catch { ... } block.
Such a block is a valid single statement, but if you put a ; at the
end of the catch block, that semicolon terminates the if statement.

If you want to write code this way, then don't put a semicolon after
the BOOST_REQUIRE_THROW macro.

>To make it work, we need to put explicit block:

That's one way to make it work, and its one reason why always using
{}s for control structures is recommended when those control
structures contain macros.

>Wouldn't it be possible to add this block in the macro so library users 
>don't have to care about?

The macro could be enclosed in a do { .... } while (0) construct in
order to make it syntactically appear more like a single statement
that is terminated with a semicolon.  File a bug report on the boost
bug tracker.
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