header-files

I have a plain C code with *.c and *.h files in the workspace. I have a header file 1.h declaring some structure as struct my1 { int a; .. .. }my_t; But when i try to declare a variable of type struct my1 in another header file 2.h as follows:- struct my1 variable1; It gives error at this declaration point. Looks like my1 is undefined here in 2.h file. In file 1.h I need to include 2.h, so in file 2.h I cannot include 1.h, for fear of recursive inclusion. My question is:- What do i need to declare to resolve the compilation error in this case? This whole thing made me think about further

Summary : when I try cross-compiling a .go source file that includes a C file somewhere in the file chain, targeting Windows AMD64 from a Mac host, I get: /usr/local/go/src/runtime/cgo/gcc_windows_amd64.c:8:10: fatal error: 'windows.h' file not found Purely Go code seems to cross compile without error; is there a way to get the proper header files for cross compilation when C files are involved? More details : I installed LiteIDE on my Mac for working on some .go projects, and LiteIDE makes it relatively simple to target other platforms as build targets. I tested it on a small test project I

This question already has an answer here: One definition rule and different class definitions in two translation units 1 answer For example I have 2 cpp files: f1.cpp and f2.cpp, and also a header file: xxx.h. f1.cpp has the following source code: #include <iostream> #include "xxx.h" using namespace std; int main () { rect rplace; polar pplace; cout<<"Enter the x and y values: "; while (cin>>rplace.x>>rplace.y) { pplace=rect_to_polar(rplace); show_polar(pplace); cout<<"Next two numbers (q to quit): "; } cout<<"Done.\n"; return 0; } f2.cpp source code: #include <iostream> #include <cmath>

Assume I have a.h which includes the following: <stdbool.h> <stddef.h> <stdin.h> Assume I also have b.h which also includes <stdbool.h> . If a.h has the #ifndef preprocessor definition statement in it and b.h doesn't. Will a.h include only what hasn't been included in b.h ? So when b.h includes a.h , will a.h include stddef.h and stein.h and not re-include stdbool.h or are those preprocessor definition functions only used to see whether this whole class is redefined, and not specific functions within it? EDIT: Also, assume b.h includes another header file which includes stdbool.h -that makes b

I have a simple program, which I copied exactly from the example in http://www.learncpp.com/cpp-tutorial/19-header-files/ because I'm learning how to make c++ programs with multiple files. The program compiles but when building, the following error appears: /tmp/ccm92rdR.o: In function main: main.cpp:(.text+0x1a): undefined reference to `add(int, int)' collect2: ld returned 1 exit status Here's the code: main.cpp #include <iostream> #include "add.h" // this brings in the declaration for add() int main() { using namespace std; cout << "The sum of 3 and 4 is " << add(3, 4) << endl; return 0; }

At a high level, I understand we use #include statements to make code from other files available to the current file. But I don't understand why we include a header file, which contains declarations but no definitions. Maybe I need to learn more about the compilation/linking process to fully understand the mechanics, but is there a high level concept I'm failing to grasp at the outset? Edit : All the answers helped clarify my question, which boils down to: once we've notified the compiler that a function is defined elsewhere, how does it figure out where to find that definition? Because if you