Mixed compilation of C and CC

Problem principle

I always thought gcc The compiled file is C Type object file , It has nothing to do with the suffix of the source file . When doing a small experiment this time, I found that the form of the target file is determined by the suffix .

start.h

void start();

start.c

#include <stdio.h>
void start(){
    
    printf("start\n");
}

test.cc

#include <stdio.h>
#include <string.h>
#include "start.h"
int main(){
    
    printf("main\n");
    start();
}

*  personal_use gcc -c start.c test.cc 
*  personal_use ld start.o test.o -lc
ld: warning: cannot find entry symbol _start; defaulting to 00000000004002c0
test.o: In function `main': test.cc:(.text+0x11): undefined reference to `start()'
*  personal_use nm start.o
                 U _GLOBAL_OFFSET_TABLE_
                 U puts
0000000000000000 T start
*  personal_use nm test.o
                 U _GLOBAL_OFFSET_TABLE_
0000000000000000 T main
                 U puts
                 U _Z5startv

It can be seen that although they are all used gcc Compilation of , however test.cc The target file for is obviously cpp Formal ( its start Functional symbol It's decorated ), and start.c It is c Form of object file .
So when linking ,test.cc I can't find it _Z5startv This symbol , because test.o There is symbol Name is start .
To sum up , The essence of the problem is actually c and cpp The handling of symbols is different ,cpp Will be embellished with symbols , and c Can't , As a result, the same function in the source code will be different when it becomes a symbol , Cause ambiguity .

resolvent

1. The simplest thing is to change them into Chengdu c Files or both cpp file , Of course, you can also use both g++ Compile Links ( All become cpp Type object file or c Type object file )

2. You can put test.cc Modify your file

   #include <stdio.h>
   #include <string.h>
   #ifdef __cplusplus
   extern "C"
   {
         
   #endif
   #include "start.h"
   #ifdef __cplusplus
   }
   #endif
   int main(){
         
       printf("main\n");
       start();
   }
   

   In this way test.cc As stated in start The function uses c Type symbol, No ambiguity .