error about compiling multi files on vscode - c

Question

I'm a beginner and I tried to run a simple project but received
o:main.c:(.text+0xde): undefined reference to `max'collect2.exe: error: ld returned 1 exit status.
I have searched on the Internet for hours but still failed. I really need your help. Thanks
my project :
my first try
I searched on the Internet and realized visual studio code compile one file one time. So I modify my tasks.json as follows
{
"tasks": [
{
"type": "cppbuild",
"label": "C/C++: gcc.exe 生成活动文件",
"command": "C:\\TDM-GCC-64\\bin\\gcc.exe",
"args": [
"-fdiagnostics-color=always",
"-g",
"${file}",
//I modify the following sentences as
"${fileDirname}\\function.c",
"${fileDirname}\\main.c",
"${fileDirname}\\main.h",
"-o",
"${fileDirname}\\${fileBasenameNoExtension}.exe"
],
"options": {
"cwd": "${fileDirname}"
},
"problemMatcher": [
"$gcc"
],
"group": {
"kind": "build",
"isDefault": true
},
"detail": "调试器生成的任务。"
}
],
"version": "2.0.0"
}
But I still received
C:/TDM-GCC-64/bin/../lib/gcc/x86_64-w64-mingw32/10.3.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\DELL\AppData\Local\Temp\ccZp5xjY.o:main.c:(.text+0xde): undefined reference to `max'
collect2.exe: error: ld returned 1 exit status
by the way, my project :
enter image description here
and my settings
enter image description here
2.my second try
I use the MakeFile but still the same error(another project but also a simple one)
MakeFile
sum : main.o sum.o
gcc main.o sum.o -o sum
main.o : main.o sum.h
gcc -c main.c
sum.o : sum.c sum.h
gcc -c sum.c
main.c
#include <stdio.h>
#include "sum.h"
int main()
{
printf("%d\n", sum(8,3));
// printf("1");
return 0;
}
sum.c
#include "sum.h"
int sum(int a, int b)
{
return a + b;
}
sum.h
int sum(int a, int b);
error
enter image description here
so I doubt if I should adjust some settings of vscode

Answer 1

Undefined reference errors happen when the compiler can't find the function that you are referencing. This is usually due to missing/incorrect arguments in one's Makefile.
I see you have a header file in the arguments of tasks.json, which is unnecessary.
EDIT: You did not put '-o' as an argument for main.o and sum.o You also put main.o as a required file for main.o, which wont work.
FIX:
sum: main.o sum.o
gcc -o sum main.o sum.o
main.o: main.c
gcc -o main.o -c main.c
sum.o: sum.c
gcc -o sum.o -c sum.c