Re: [O] org-babel C math.h issue

[Thierry Banel]

Seems good. I tested it. As a refinement, the associated documentation should be updated (but that is a separate patch). http://orgmode.org/worg/org-contrib/babel/languages/ob-doc-C.html Thierry Le 11/03/2016 20:14, Oz Ben-Ami a écrit : Thanks for the response. On my machine, I get the undefined references even with GCC 5 (gcc version 5.2.1 20151010 (Ubuntu 5.2.1-22ubuntu2)), if I put -lm before the source file name. As far as a patch, I can try but this would be my first time really playing with org-mode code. As far as I can see, I would need to add the following lines in ob-C.el: L133: (libs (cdr (assoc :libs params)))          (libs (mapconcat 'identity                (if (listp libs) libs (list libs)) " ")) L142: (format "%s -o %s %s %s %s" ;; (added %s) L147: libs Am I missing anything? Oz On Fri, Mar 11, 2016 at 1:52 PM, Thierry Banel <tbanelweb...@free.fr> wrote: To summarize this thread: It seems there was an issue long ago. Version 5 of GCC magically fixed it. But it is still here for older compilers. ------------------------- To debug, execute the following piece of lisp code:     (defadvice org-babel-eval (before xxx (cmd body))       ""       (message "org-babel-eval : %s" cmd))     (ad-activate 'org-babel-eval) The actual compilation command will be displayed in the *Messages* buffer. With your example, we get    gcc -o /tmp/babel-8412zIw/C-bin-8412IZR -lm /tmp/babel-8412zIw/C-src-84127OL.c -------------------------- You are right, Oz, this can be fixed in line 147. But :flags is intended for flags like -g or -O, which need to appear before the source file. Probably we are missing an additional flag, which could be named :libs Then your example would be:   #+BEGIN_SRC C :includes '(<math.h> <stdio.h>) :libs -lm   int i=9;   printf("%d\n",(int)sqrt(i));   #+END_SRC -------------------------- Oz, do you think you would be able to provide a patch? The way to contribute is documented here: http://orgmode.org/worg/org-contribute.html#orgheadline1 Thanks for reporting. Thierry Le 06/03/2016 23:44, Oz Ben-Ami a écrit : > Hi, > > I'm a new org user, and I'm sorry if I'm missing something obvious. > When executing a C code snippet with org-babel, that contains a math > function, I get the famous "undefined reference" errors. I tried > adding ":flags -lm", but that doesn't help. Looking at the code, it > seems the -lm flag is inserted in the wrong place, before the source > file. An easy change would be in line 147 of ob-C.el version > 8.3.4-634, moving "flags" to after the source file. This seems to > work, but I don't know if it would break anything else. > > A minimal working example, attached, includes the following snippet: > > #+BEGIN_SRC C :includes '(<math.h> <stdio.h>) :flags -lm > int i=9; > printf("%d\n",(int)sqrt(i)); > #+END_SRC > > Note the issue disappears if constants are directly used rather than > variables, presumably because the function call is optimized away > entirely. > > Any thoughts are appreciated. > > Oz