[cfe-dev] clang-format, recognizing alternative binary operator tokens

[Philip Reames]

On 05/03/2014 02:52 PM, Bobby Moretti wrote:
> Hello,
>
> clang-format does a really nice job breaking lines with boolean binary
> operators, e.g., && and ||.
>
> The C++ standard provides alternative keywords for these operators
> (and, or). I think clang-format should be able to treat these
> alternative keywords the same as the corresponding binary operators.
> However, with these alternative keywords, clang-format makes
> completely different whitespace choices. For example, using
> clang-format 3.5 from svn r207601, with the default LLVM style options
>
> void foo(void) {
>    if (call_some_function() >
>        0 and(some_other_function_result() ==
>              0 or yet_another_result or(something_else == 1))) {
>    }
>
>    if (call_some_function() > 0 &&
>        (some_other_function_result() == 0 || yet_another_result ||
>         (something_else == 1))) {
>    }
> }
>
> I did some investigation to see what might be causing this behavior.
> It boils down to the LangOptions returned by getFormattingOptions() in
> Format.cpp line 1848. If I add
>
> LangOpts.CXXOperatorNames = 1;
>
> to that function, then clang-format outputs the much more pleasing
>
> void foo(void) {
>    if (call_some_function() > 0 and
>        (some_other_function_result() == 0 or yet_another_result or
>         (something_else == 1))) {
>    }
>
>    if (call_some_function() > 0 &&
>        (some_other_function_result() == 0 || yet_another_result ||
>         (something_else == 1))) {
>    }
> }
>
> Of course, this should probably not always be enabled.
>
> One option would be to only enable this option if LS_Cpp03 or LS_Cpp11
> were chosen. But C users #including <iso646.h> might want this option,
> and not all C++ users would want it (since for example, MSVC++ does
> not recognize these unless using standards compliant mode).
>
> So another option would be to add a format style option to selectively
> enable this behavior.
>
> Would such a change to clang-format be welcome? If so, what would be
> the preferred implementation?
>
> Thanks,
This seems like a useful enhancement.  Why don't you either a) file a 
bug, or b) propose a patch?

I would suggest that we should default to recognizing the keyword 
whenever it's legal for the language being compiled.  We shouldn't need 
to opt-in to standard defined language features.  I don't really see any 
downside to having it enabled.  If we support a MSVC++ compatibility 
mode (do we?), it should be controlled by that flag.

Philip