Very informative answer. I looked back on the examples, and it seems
they were building individual object files, as you say. This cleared up
my confusion, thanks a million!
On 2/11/2014 2:28 PM, Jukka Jylänki wrote:
The .cpp files are never included by other files (well you could, but
by good organization practices they don't). They are the 'starting
points' of compilation units, which go on to include headers. Each
.cpp file is compiled separately as their own compilation unit, and
the results are linked together. You must have somehow confused the
examples you looked at - all C++ compilers do this: you pass all the
.cpp files to the compiler either via a single "cc a.cpp b.cpp c.cpp
-o a.out" directive, or via separate directives that create object
files "cc a.cpp -o a.obj;cc b.cpp -o b.obj;cc c.cpp -o c.obj" and then
finally combine them together with "cc a.obj b.obj c.obj -o a.out".
Visual Studio traditionally uses the suffix .obj for intermediate
object files, GCC uses .o, emcc can use either. It is also possible to
make more complex build hierarchies by compiling multiple object files
to static libraries, and then finally combine the individual static
libraries to produce the final executable. Perhaps the examples you
were looking at all built individual object files, and therefore only
ever called emcc with a single .cpp file at a time?
2014-02-11 20:55 GMT+02:00 Jack Arrington <[email protected]
<mailto:[email protected]>>:
First I should say that I am far from a C++ ninja, and I've only
compiled a few simple things with emscripten thus far.
So I have my main.cpp file, and a class called Foo in Foo.h and
Foo.cpp. main.cpp includes Foo.h and Foo.cpp includes Foo.h, but
when I compile, I get the error: "warning: unresolved symbol:
_ZN5FooC1EV". My understanding was that this was the standard way
of doing things in C++. /However, /when I switch the contents of
Foo.h and Foo.cpp to a function declaration and implementation,
respectively, I get no such error. When I change the contents of
my Makefile from "emcc -g4 src/main.cpp -o out/main.js" to "emcc
-g4 src/main.cpp src/Foo.cpp -o out/main.js", everything works.
This makes sense to me, since Foo.cpp is not actually getting
/included /anywhere in the code. But what confuses me is that all
the emscripten examples I have read do not seem to do this, and
code like this works with cl(Microsoft's C++ compiler).
Did I miss something here? Am I making a dumb mistake? Any help is
appreciated.(below is posted my code)
Main.cpp:
#include <iostream>
#include <stdio.h>
#include "Foo.h"
int main(int argc, char const *argv[])
{
Foo f;
printf("%i\n", f.bar);
return 0;
}
Foo.h:
#ifndef FOOH
#define FOOH
#pragma once
class Foo
{
public:
Foo();
~Foo();
int bar;
};
#endif
Foo.cpp:
#include "Foo.h"
Foo::Foo()
{
printf("Hello\n");
bar = 12;
}
Foo::~Foo()
{
}
Makefile:
emcc -g4 src/main.cpp src/Foo.cpp -o out/main.js
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