Re: CEDET calls cpp -E -dM -x c++ /dev/null

[Lennart Borgman]

On Fri, Jul 3, 2009 at 2:46 AM, Miles Bader<address@hidden> wrote:
> Lennart Borgman <address@hidden> writes:
>> Thanks, there are more env vars for this, see
>> http://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html
>>
>> From the page http://www.mingw.org/wiki/IncludePathHOWTO it looks like
>> the way to get the include path used by gcc is something like
>>
>>    touch temp.c
>>    gcc -v -c temp.c -o NUL (or /dev/null)
>
> Better to use something like this:  gcc -v -E -x c /dev/null
> which doesn't require an input file or run unnecessary passes of the compiler.
> (substitute NUL on windows)

Yes, that is better. Thanks. I tried to use it like this

(defun semantic-gcc-query (gcc-cmd &rest gcc-option)
  "Query gcc.  Return a list of configurations.
GCC-CMD is an optional command to execute instead of \"gcc\""
  ;; $ gcc -v
  ;;
  (let ((buff (get-buffer-create " *gcc-query*")))
    (save-excursion
      (set-buffer buff)
      (erase-buffer)
      (condition-case nil
          (apply 'call-process gcc-cmd nil buff nil gcc-option)
        (error ;; Some bogus directory for the first time perhaps?
         (let ((default-directory (expand-file-name "~/")))
           (condition-case nil
               (apply 'call-process gcc-cmd nil buff nil gcc-option)
             (error ;; gcc doesn't exist???
              nil)))))
      (prog1
          (buffer-string)
        (kill-buffer buff)
        ))))

(defun semantic-gcc-get-include-paths (lang)
  (let* ((gcc-cmd (cond
                   ((string= lang "c") "gcc")
                   (t (error "Unknown lang: %s" lang))))
         (gcc-output (semantic-gcc-query gcc-cmd "-v" "-E" "-x" lang)))
    ))

However calling (semantic-gcc-get-include-paths "c") does not catch
the output I want to gcc-output. I get

Result: "gcc.exe: warning: `-x c' after last input file has no
effect\nReading specs from
c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs\nConfigured with:
../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld
--with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw
--enable-threads --disable-nls
--enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry
--disable-shared --enable-sjlj-exceptions --enable-libgcj
--disable-java-awt --without-x --enable-java-gc=boehm
--disable-libgcj-debug --enable-interpreter
--enable-hash-synchronization --enable-libstdcxx-debug\nThread model:
win32\ngcc version 3.4.5 (mingw-vista special r3)\n"



>> I believe this works on all os:es with gcc. It seems to include CPATH
>> and C_INCLUDE_PATH etc. However do not quite understand the output and
>> how to parse it. Could someone explain?
>
> This part of the output seems to have pretty well-defined markers, and
> lists the include directories one per line:
>
>   #include "..." search starts here:
>   #include <...> search starts here:
>    /usr/local/include
>    /usr/lib/gcc/x86_64-linux-gnu/4.3.3/include
>    /usr/lib/gcc/x86_64-linux-gnu/4.3.3/include-fixed
>    /usr/include
>   End of search list.
>
> Looks easy enough to parse (since there's a space prepended to each
> directory line, you don't even have to worry about a directory called
> "End of search list.", though an embedded newline might cause a
> mess... :).

Yes, but what about the two different categories of include paths. How
 should they be handled? Just use both?


> Thanks,
>
> -Miles
>
> --
> Learning, n. The kind of ignorance distinguishing the studious.
>
>
>
>