Thanks.

[stardiviner]           <Hack this world!>      GPG key ID: 47C32433
IRC(freeenode): stardiviner                     Twitter:  @numbchild
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Blog: http://stardiviner.github.io/

On Sat, Jun 11, 2016 at 12:44 AM, Thierry Banel <tbanelwebmin@free.fr>
wrote:

> Change the first line to
>
>   #+BEGIN_SRC C *:libs -lm*
>
> This instructs the C++ compiler to link with the "m" library (mathematical
> functions).
>
> You need a pretty new version of ob-C.el, as the :libs parameter was
> introduced recently.
>
>
>
> Le 10/06/2016 14:01, numbchild@gmail.com a écrit :
>
> I have a code example like this:
>
> #+BEGIN_SRC C
> #include <stdio.h>
> #include <math.h>
>
> /* define complex struct */
> struct complex_struct {
>   double x, y;
> };
>
> /* some helper functions on complex struct */
> double real_part(struct complex_struct z) {
>   return z.x;
> }
> double img_part(struct complex_struct z) {
>   return z.y;
> }
> double magnitude(struct complex_struct z) {
>   return sqrt(z.x * z.x + z.y * z.y);
> }
> double angle(struct complex_struct z) {
>   return atan2(z.y, z.x);
> }
>
> /* helper functions to construct complex variable */
> struct complex_struct make_from_real_img(double x, double y) {
>   struct complex_struct z;
>   z.x = x;
>   z.y = y;
>   return z;
> }
>
> struct complex_struct make_from_mag_ang(double r, double A) {
>   struct complex_struct z;
>   z.x = r * cos(A);
>   z.y = r * sin(A);
>   return z;
> }
>
> /* implement complex arithemtic */
> struct complex_struct add_complex(struct complex_struct z1, struct
> complex_struct z2) {
>   return make_from_real_img(real_part(z1) + real_part(z2), img_part(z1) +
> img_part(z2));
> }
>
> int main(int argc, char *argv[]) {
>   struct complex_struct z1, z2 = {1.1, 2.4};
>
>   struct complex_struct z;
>   z = add_complex(z1, z2);
>
>   printf("%f", z);
>   return 0;
> }
> #+END_SRC
>
> But evaluate it got error:
>
> ```
> /tmp/cckFlXlJ.o: In function `magnitude':
> C-src-18467gDZ.c:(.text+0xa8): undefined reference to `sqrt'
> /tmp/cckFlXlJ.o: In function `angle':
> C-src-18467gDZ.c:(.text+0xfe): undefined reference to `atan2'
> /tmp/cckFlXlJ.o: In function `make_from_mag_ang':
> C-src-18467gDZ.c:(.text+0x174): undefined reference to `cos'
> C-src-18467gDZ.c:(.text+0x190): undefined reference to `sin'
> collect2: error: ld returned 1 exit status
> zsh:1: no such file or directory: /tmp/babel-18467-Yn/C-bin-18467tNf
> ```
>
> So I think `ob-C.el` doesn't support to load included header files.
>
> [stardiviner]           <Hack this world!>      GPG key ID: 47C32433
> IRC(freeenode): stardiviner                     Twitter:  @numbchild
> Key fingerprint = 9BAA 92BC CDDD B9EF 3B36  CB99 B8C4 B8E5 47C3 2433
> Blog: http://stardiviner.github.io/
>
>
>