[cfe-dev] Preprocessing and whitespace collapsing

Matt Fowles matt.fowles at gmail.com
Mon Jan 13 21:58:42 PST 2014


YouCompleteMe (the vim plugin) is built with a parser and completion engine
server and a client process that sits inside vim.  Not sure how far your
implementation is, but you may wish to consider sharing work it.



On Tue, Jan 14, 2014 at 12:46 AM, Anders Bakken <agbakken at gmail.com> wrote:

> Hi
> We're using to make an indexer daemon which can be queried from emacs
> (or other editors if so desired). In doing this we, for various
> reasons, preprocess the file first using internal APIs and then invoke
> clang_parseTranslationUnit on the preprocessed content. The code for
> this is here:
> https://github.com/Andersbakken/rtags/blob/multi-process/src/RTagsClang.cpp
> Starting at line 450.
> The problem we're facing is that clang seems to collapse things like this:
> struct A
> {
>     void               foo();
> };
> into this:
> struct A
> {
>     void foo();
> };
> int main()
> {
>     A a;
>     a.foo();
> }
> I realize the standard (at least according to GCC) permits this and
> that it of course would speed up parsing of the resulting code ever so
> slightly. My question is, is it possible to:
> A) Turn this behavior off with an option?
> or
> B) Someone query which lines had what amounts of space removed.
> I assume something can be done since if I let
> clang_parseTranslationUnit index it without preprocessing myself
> everything works as expected.
> From (http://gcc.gnu.org/onlinedocs/gcc-3.3/cpp/Preprocessor-Output.html)
> The ISO standard specifies that it is implementation defined whether a
> preprocessor preserves whitespace between tokens, or replaces it with
> e.g. a single space. In GNU CPP, whitespace between tokens is
> collapsed to become a single space, with the exception that the first
> token on a non-directive line is preceded with sufficient spaces that
> it appears in the same column in the preprocessed output that it
> appeared in the original source file. This is so the output is easy to
> read. See Differences from previous versions. CPP does not insert any
> whitespace where there was none in the original source, except where
> necessary to prevent an accidental token paste.
> Thanks and kudos for an awesome project.
> regards
> Anders
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
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