[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

From: Nick Dokos
Subject: Re: [O] org-babel C math.h issue
Date: Thu, 10 Mar 2016 16:19:54 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux)

Oz Ben-Ami <address@hidden> writes:

> 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));
> 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.

I can't reproduce it either (with fairly recent emacs and bleeding-edge
org-mode, but the code in question has not changed since 8.2.7 or so).

The command that is executed looks like this:

  gcc -o /tmp/babel-212464kj/C-bin-21246R6L -lm 

and that should work fine for gcc: you don't need to have the -lm after the
source file.

You can test that that's the case: put your program into a file, say foo.c, and

  gcc -o foo.out -lm foo.c

Does that give you undefined references?


reply via email to

[Prev in Thread] Current Thread [Next in Thread]