Graphviz as Library error: too many arguments to function ‘agnode’ - c

Question

I'm trying to run a example from the "Using Graphviz as a library" in http://www.graphviz.org/Documentation.php.
#include <gvc.h>
int main(int argc, char **argv)
{
Agraph_t *g;
Agnode_t *n, *m;
Agedge_t *e;
Agsym_t *a;
GVC_t *gvc;
/* set up a graphviz context */
gvc = gvContext();
/* parse command line args - minimally argv[0] sets layout engine */
gvParseArgs(gvc, argc, argv);
/* Create a simple digraph */
g = agopen("g", Agdirected);
n = agnode(g, "n", 1);
m = agnode(g, "m", 1);
e = agedge(g, n, m, 0, 1);
/* Set an attribute - in this case one that affects the visible rendering */
agsafeset(n, "color", "red", "");
/* Compute a layout using layout engine from command line args */
gvLayoutJobs(gvc, g);
/* Write the graph according to -T and -o options */
gvRenderJobs(gvc, g);
/* Free layout data */
gvFreeLayout(gvc, g);
/* Free graph structures */
agclose(g);
/* close output file, free context, and return number of errors */
return (gvFreeContext(gvc));
}
I'm compiling and linking with : gcc -Wall pkg-config libgvc --cflags --libs *.c -o EXE -lgvc
and then I see this result:
graph.c: In function ‘main’:
graph.c:14:18: error: ‘Agdirected’ undeclared (first use in this function)
graph.c:14:18: note: each undeclared identifier is reported only once for each function it appears in
graph.c:15:2: error: too many arguments to function ‘agnode’
In file included from /usr/include/graphviz/types.h:717:0,
from /usr/include/graphviz/gvc.h:20,
from graph.c:1:
/usr/include/graphviz/graph.h:185:22: note: declared here
graph.c:16:2: error: too many arguments to function ‘agnode’
In file included from /usr/include/graphviz/types.h:717:0,
from /usr/include/graphviz/gvc.h:20,
from graph.c:1:
/usr/include/graphviz/graph.h:185:22: note: declared here
graph.c:17:2: error: too many arguments to function ‘agedge’
In file included from /usr/include/graphviz/types.h:717:0,
from /usr/include/graphviz/gvc.h:20,
from graph.c:1:
/usr/include/graphviz/graph.h:192:22: note: declared here
graph.c:7:11: warning: unused variable ‘a’ [-Wunused-variable]
graph.c:6:12: warning: variable ‘e’ set but not used [-Wunused-but-set-variable]
Could anyone help me understand what is going on? Why the compiler is complaining about those arguments in those functions?
Thank you!!!!

Answer 1

I saved your code as g.c, then issued this command line
gcc -Wall `pkg-config libgvc --cflags --libs` g.c -o EXE -lgvc
that yields
g.c: In function ‘main’:
g.c:14:5: error: too few arguments to function ‘agopen’
/usr/local/include/graphviz/cgraph.h:266:18: note: declared here
g.c:7:14: warning: unused variable ‘a’ [-Wunused-variable]
g.c:6:15: warning: variable ‘e’ set but not used [-Wunused-but-set-variable]
then I added the miss parameter
g = agopen("g", Agdirected, 0);
and the miss library
gcc -Wall `pkg-config libgvc --cflags --libs` g.c -lgvc -lcgraph
now the code compile and link with just 2 warnings:
g.c: In function ‘main’:
g.c:7:14: warning: unused variable ‘a’ [-Wunused-variable]
g.c:6:15: warning: variable ‘e’ set but not used [-Wunused-but-set-variable]
I think it works because I've built graphviz from source, then pkg-config is up-to-date...
The program still need some debug, running it i get:
./a.out
There is no layout engine support for "a.out"
Use one of: circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi
Error: Layout was not done. Missing layout plugins?
The message is because by default the layout engine use the exe name (i.e. a.out, default of gcc compile-and-link) as layout string...