Re: [Boost-build] Preprocessed output

Subject: Re: [Boost-build] Preprocessed output
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-03-29 16:08:01

AMDG

On 03/29/2011 12:39 PM, Edward Diener wrote:
> On 3/29/2011 2:34 PM, Steven Watanabe wrote:
>> On 03/29/2011 11:10 AM, Edward Diener wrote:
>>> How do I tell Boost Build to generate preprocessed output, either when
>>> using the 'compile' rule or using some other rule ?
>>>
>>> I tried, for gcc, adding an -E to the command line as a cxxflag but the
>>> compile rule still attempted to compile the file and no output was
>>> produced. I need to send preprocessed output to a file without compiling
>>> the preprocessed output.
>>>
>>
>> I don't think there's a way to do this at present.
>
> That is unfortunate. I guess I am forced to do it by hand after manually
> copying the command-line output of the 'compile' rule for a given
> compiler and altering it as necessary.
>
>> It shouldn't be too hard to add, though. There would
>> need to be a new target type and rules in the toolset
>> modules to generate it.
>>
>> I needed this for my template profiler, but I only
>> implemented it for msvc and gcc and not in a particularly
>> reusable way.
>
> Right now I only need it for msvc and gcc on Windows also.
>

I'm probably not going to get to this
immediately, but if you file a trac
ticket, so I don't forget, I'll try
to get it done within a few weeks.

>>
>> a) Does it need to distinguish between C and C++?
>> I think so, since we want exactly the same compiler
>> flags that would be passed to create an object file.
>
> That would be ideal, if the preprocessor really works differently
> depending on whether the compiling mode is for C or C++. I was not aware
> that it does.
>

It should mostly be the same.  Except for:
a) Effects of cxxflags vs. cflags.
b) #ifdef __cplusplus.

>> b) What should the name of the type be? This will
>> also control the name of the main target rule.
>
> preproc
>

Normally the name of the type is
the same as the default extension.
If we use something different, I'd
personally rather spell out the whole word.

Actually, we probably want to use
a single rule for C and C++ and deduce
which is which from the source.  We
should also propagate that information
through, so that a preprocessed file
can be compiled correctly.

>> c) What should the extension be. I know msvc uses .i
>> by default for preprocessor output. Unless they're
>> already used by something else, we could make it
>> .i and .ipp.
>
> I think that is fine.
>

On the other hand, .ipp is used in a few places in
Boost with a different meaning, so it's probably
not a good choice.  Would it be confusing to use
.i for everything?  Do you know of any other
common convention?

In Christ,
Steven Watanabe