multiple-definition-error

问题 So my program is working fine. Compiling, linking, running, the works. Then, I decide to add a simple function to one of my files, like this: #ifndef UTILITY_HPP #define UTILITY_HPP /* #includes here. There's no circular include, I've checked. */ namespace yarl { namespace utility { (several function declarations and definitions) bool isVowel(const char c) { if(c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') return true; else return false; } } } #endif That function definition is

问题 I have these files consumer.cpp consumer.hpp defines.hpp main.cpp makefile producer.cpp producer.hpp here's the file defines.hpp #ifndef DEFINES_HPP #define DEFINES_HPP #include <cassert> #include <pthread.h> #include <queue> #include <stdlib.h> #include <string> #include <unistd.h> pthread_mutex_t set_queue_mutex = PTHREAD_MUTEX_INITIALIZER; pthread_cond_t condition_var = PTHREAD_COND_INITIALIZER; std::queue<int> q; #endif // DEFINES_HPP This defines.hpp file is included in the producer.hpp

问题 i would like to know if there is an alternative for __attribute__((selectany)) in linux ? i would like to define something like that: char * a[] = { "qwe", "zxc" }; in a header file and include it in many .c files which would be linked together. so the linker will see more than one definition of "a" and therefor will not link. i've read of this attribute (selectany), which will use only the first seen definition of "a", unfortunately it is only for ms windows. so the question is: is there an

问题 I know the only way to pass a string literal as template argument is to declare it before: file a.h #ifndef A_H #define A_H #include <string> char EL[] = "el"; template<char* name> struct myclass { std::string get_name() { return name; } }; typedef myclass<EL> myclass_el; #endif file a.cpp #include "a.cpp" main.cpp #include "a.h" ... g++ -c a.cpp g++ -c main.cpp g++ -o main main.o a.o and I got: a.o:(.data+0x0): multiple definition of `EL' main.o:(.data+0x0): first defined here collect2: ld

问题 I'm using multiple C++ files in one project for the first time. Both have need to include a protected (#ifndef) header file. However, when I do that, I get a multiple definition error. What I have is two one .cpp file that calls the header directly, and one indirectly (Another include includes it) and then two other header files that include it. So what do I need to do to get rid of the error? ERROR: obj\Debug\main.o||In function Z14sortLibQtyTest4BookS_':| [PATH]\miscFuncs.h|16|multiple

问题 I'm using multiple C++ files in one project for the first time. Both have need to include a protected (#ifndef) header file. However, when I do that, I get a multiple definition error. What I have is two one .cpp file that calls the header directly, and one indirectly (Another include includes it) and then two other header files that include it. So what do I need to do to get rid of the error? ERROR: obj\Debug\main.o||In function Z14sortLibQtyTest4BookS_':| [PATH]\miscFuncs.h|16|multiple

问题 I'm using multiple C++ files in one project for the first time. Both have need to include a protected (#ifndef) header file. However, when I do that, I get a multiple definition error. What I have is two one .cpp file that calls the header directly, and one indirectly (Another include includes it) and then two other header files that include it. So what do I need to do to get rid of the error? ERROR: obj\Debug\main.o||In function Z14sortLibQtyTest4BookS_':| [PATH]\miscFuncs.h|16|multiple

问题 Beside moving the hello() function into another source (.cpp) file or renaming the function. Is there any other methods to avoid the linking error? staticLibA.h #ifndef _STATIC_LIBA_HEADER #define _STATIC_LIBA_HEADER int hello(void); int hello_staticLibA_only(void); #endif staticLibA.cpp #include "staticLibA.h" int hello(void) { printf("\nI'm in staticLibA\n"); return 0; } int hello_staticLibA_only(void) { printf("\nstaticLibA: hello_staticLibA_only\n"); return 0; } output: g++ -c -Wall -fPIC

问题 I'm new to programming and currently I'm learning C programming. I'm writing codes on the code blocks and in it using GCC compiler. When I create a new project, (as you know it creates main.c file with it) and due to that I'm not able to compile another file in that project. File 1: #include<stdio.h> int main() { int a,b,c,d; printf("Enter three numbers\n"); scanf("%d%d%d",&a,&b,&c); d=a; if(b>d) d=b; if(c>d) d=c; printf("\n The maximum of three numbers is %d",d); } File 2: main.c #include

问题 I have been trying to use extern in order to use variable that is previously defined. I have not used extern before and now I need to use it in order to define variable just once and use them across multiple files I have written minimized version of code for this question. I have four files lib.h #ifndef LIB_H #define LIB_H #include <iostream> namespace lib { extern bool initialized; bool initialized = false; static void isInit(char* parent) { std::cout << "Library for [" << parent << "]