Question

我正在尝试在http://www.graphviz.org/Documentation.php中的“将Graphviz用作库”中运行示例。

#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));
}

我正在编译和链接：gcc -Wall pkg-config libgvc --cflags --libs * .c -o EXE -lgvc

然后我看到了这个结果：

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]

有谁能帮我理解发生了什么？为什么编译器在这些函数中抱怨这些参数？

谢谢!!!!

Answer 1

我将您的代码保存为g.c，然后发出此命令行

gcc -Wall `pkg-config libgvc --cflags --libs` g.c -o EXE -lgvc

产生

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]

然后我添加了miss参数

g = agopen("g", Agdirected, 0);

和miss library

gcc -Wall `pkg-config libgvc --cflags --libs` g.c -lgvc -lcgraph

现在代码编译并链接只有2个警告：

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]

我认为它有效，因为我从源代码构建了graphviz，然后pkg-config是最新的...... 该程序仍然需要一些调试，运行它得到：

./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?

该消息是因为默认情况下布局引擎使用exe名称（即a.out，默认为gcc compile-and-link）作为布局字符串......

Graphviz as Library错误：函数'agnode'的参数太多

1 个答案: