multiple-definition-error

I'm writing some code where I need to have a class variable that's a static int array. I understand that I can do this with something like this in the header file, A.h: #ifndef A_H_ #define A_H_ class A { public: static const int a[]; }; const int A::a[] = {1,2}; #endif This works just fine if I'm then including this header in only one other file, something like the following, main.cpp: #include "A.h" #include <iostream> using namespace std; int main() { A myA; cout << "0: " << myA.a[0] << endl; cout << "1: " << myA.a[1] << endl; } But suppose I need my class A to be a bit more complicated,

I have 3 projects: Server , Client and Commons . Making header & source pairs in Commons doesn't cause any problems and I can access the functions freely from both Server and Client . However, for some reason making additional source/header files within Server or Client project always causes multiple definition of (...) and first defined here errors. Example: commands.h (in root dir of the Client project) #ifndef COMMANDS_H_ #define COMMANDS_H_ #include "commands.c" void f123(); #endif /* COMMANDS_H_ */ commands.c (in root dir of the Client project) void f123(){ } main.c (in root dir of the

The linker is reporting multiply defined errors for an inline function. I have the following code in a header file: struct Port_Pin { volatile uint32_t * port_addr_set_value; //!< Writing the pin value here sets the pin to high. volatile uint32_t * port_addr_clr_value; //!< Writing the pin value to this port clears the pin to low. volatile uint32_t * port_addr_read_value; //!< Address to read pin value. volatile uint32_t * port_addr_enable; //!< Writing the pin value here enables the pin (for reading or writing). volatile uint32_t * port_addr_disable; //!< Writing the pin value here disables

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.: UTILS718171_H_) but it doesn't work. Still, the compiler complains: /tmp/ccOE6i1l.o: In function `compare_int':

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++? CB Bailey It's not strictly legal. int a; is a tentative definition in C. You are allowed multiple tentative definitions and at most one non-tentative definition per translation unit of each object

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 here| There is no way that I'm multiply defining test (although I don't know where the underscore is