multiple-definition-error

Multiple definition and header-only libraries

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问题 I have a C program with several c and h files. I decided to make one part of the program 'header-only' so I moved the code from c to h. Now I'm getting multiples definition problems and I have no idea why. e.g.: main.c includes utils.h vector.c includes utils.h I moved everything in utils.c to utils.h (and of course removed utils.c from the project). utils.h starts with #ifndef UTILS_H_ #define UTILS_H_ // and end with: #endif To be sure my guard was unique I tried changing it (e.g.:

c & c++ default global variable linkage, multiple declaration & definition problem

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问题 For example: code1.c / .cpp int a; // ... and so on code2.c / .cpp int a; int main(void) { return 0; } go to compile: $gcc code1.c code2.c # this is fine $ $g++ code1.cpp code2.cpp # this is dead /tmp/ccLY66HQ.o:(.bss+0x0): multiple definition of `a' /tmp/ccnIOmPC.o:(.bss+0x0): first defined here collect2: ld returned 1 exit status Is there any global variable linkage difference between C & C++? 回答1: It's not strictly legal. int a; is a tentative definition in C. You are allowed multiple

How to prevent multiple definitions in C?

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问题 I'm a C newbie and I was just trying to write a console application with Code::Blocks. Here's the (simplified) code: main.c: #include <stdio.h> #include <stdlib.h> #include "test.c" // include not necessary for error in Code::Blocks int main() { //t = test(); // calling of method also not necessary return 0; } test.c: void test() {} When I try to build this program, it gives the following errors: *path*\test.c|1|multiple definition of `_ test'| obj\Debug\main.o:*path*\test.c|1|first defined

Repeated Multiple Definition Errors from including same header in multiple cpps

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So, no matter what I seem to do, I cannot seem to avoid having Dev C++ spew out numerous Multiple Definition errors as a result of me including the same header file in multiple source code files in the same project. I'd strongly prefer to avoid having to dump all my source code into one file and only include the header once, as that's going to make my file very long and difficult to manage. Essentially, this is what's going on: #ifndef _myheader_h #define _myheader_h typedef struct MYSTRUCT{ int blah; int blah2; } MYSTRUCT; MYSTRUCT Job_Grunt; MYSTRUCT *Grunt = &Job_Grunt; MYSTRUCT Job_Uruk;

Repeated Multiple Definition Errors from including same header in multiple cpps

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问题 So, no matter what I seem to do, I cannot seem to avoid having Dev C++ spew out numerous Multiple Definition errors as a result of me including the same header file in multiple source code files in the same project. I\'d strongly prefer to avoid having to dump all my source code into one file and only include the header once, as that\'s going to make my file very long and difficult to manage. Essentially, this is what\'s going on: #ifndef _myheader_h #define _myheader_h typedef struct