Eclipse C编译器抛出错误

Question

我试图在Mac 10.12.6上的Eclipse Oxygen.1中编译helloworld.c

#include <stdio.h>
#include <stdlib.h>
int main(){
    printf("Hello World!");
    return 0;
}

它会引发这样的错误：

20:41:02 **** Incremental Build of configuration Debug for project HelloWorld ****
make all 
Building target: HelloWorld
Invoking: Cross GCC Linker
gcc  -o "HelloWorld"  ./helloworld.o   
Undefined symbols for architecture x86_64:
  "_main", referenced from:
     implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [HelloWorld] Error 1

20:41:03 Build Finished (took 938ms)

我很确定问题不是代码本身，而是什么？