Inserting function calls in the gimple - c++

Question

I'm having problems figuring out how to do the next thing.
I have the following code:
test.cpp
#include <stdio.h>
void
function(void) {printf("Hellow ");}
int main(void) {
printf("World\n");
return 0;
}
And I want to transform it into the next one:
#include <stdio.h>
void
function(void) {printf("Hellow ");}
int main(void) {
function();
printf("World\n");
return 0;
}
with a gcc plugin.
The code that doesn't work in my plugin is this one:
...
tree function_fn;
tree function_fn_type;
function_fn_type=build_function_type_list(void_type_node, void_type_node, NULL_TREE);
function_fn = build_fn_decl ("function", function_fn_type);
gimple call = gimple_build_call (funcion_fn, 0);
gsi_insert_before (&gsi, call, GSI_NEW_STMT);
...
Then when I compile test.cpp with the plugin i have the next error message:
/tmp/cc2VRszt.o: In function main':
test.cpp:(.text+0x60): Undefined reference tofunction'
Anyone can help me?

Answer 1

You're building a function declaration, and inserting a call to a function based on the declaration, but unless you've defined that function in another translation unit you link to, it will be unresolved. If you want a plugin to insert a definition in the same translation unit like in your example, this guide for front-end developers would be a good start:
http://www.tldp.org/HOWTO/GCC-Frontend-HOWTO-7.html