Re: Problem compiling C++ in Org-mode

[Michael Hannon <jm_hannon@yahoo.com>]

Olaf Meeuwissen wrote:

>  Michael Hannon <jm_hannon@yahoo.com> writes:

>> Greetings.  I'm having a problem compiling a C++ source-code block in
>> Org-mode.  The same C++ code compiles and runs in the shell.
>>
>> The issue seems to relate to local include files.  [...snip...]
>> What am I missing?
>
>> /tmp/babel-245846_d/C-src-24584NIQ.cpp:7:26: fatal error: OtherStuff.cpp: No
>> such file or directory
>> compilation terminated.
>> /bin/bash: /tmp/babel-245846_d/C-bin-24584aSW: Permission denied

> Compilation is taking place in a temporary directory, miles away from
> where your org file lives.

>> ########## Org-mode compile uses same option as shell compile:
>>
>> org-babel-C++-compiler is a variable defined in `ob-C.el'.
>> Its value is "g++ -std=c++0x"

> The current directory is not specified in the include path.  You would
> need to add a -I option to set the (absolute path to the) directory the
> org file is in.  If you have all your org files in ~/org, you could try
> "g++ -std=c++0x -I~/org".

Thanks, Olaf.  That does fix the problem, and in some sense that's the obvious
solution.  On the other hand, it does seem strange to me that the end user
should have to specify the include directory.  I.e., Emacs clearly knows the
current directory ("M-x pwd", for instance), and the C++ compiler "knows" to
look in the current directory for include files enclosed in quote marks.  I
assumed that the compilation process in Org-mode would include steps similar
to:

    + remember current directory
    + write contents of source block to obscure location in /tmp
    + compile source block in obscure location,
          but remembering the starting directory for such things
          as include files

Obviously I was wrong, but it still seems a reasonable approach.

-- Mike