Use clang preprocessor to concatenate C++ source files into one [duplicate] - c++

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Merge C++ files into a single source file
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In the context of a coding contest, I must copy/paste all my C++ code in a single html input form, the code being compiled remotely. With the code getting bigger, I'd like to split the code into several files.
So, I have several C++ source files, one is main.cc and some others headers such as f.h.
I'd like these source files to be concatenated in a single source file allinone.cc with so that i can compile with clang++ allinone.cc.
I guess this can be achieved using clang preprocessor.
A minimal example would be:
main.cc
#include <iostream>
using namespace std;
#include "f.h"
int main() {
f();
}
f.h
#pragma once
#include <iostream>
using namespacestd;
void f() {
cout <<
}
The closest I could get is with :
clang -E -nostdinc main.cc | grep -v "^#" > allinone.cc
which produces:
#include <iostream>
^~~~~~~~~~
1 error generated.
using namespace std;
using namespacestd;
void f() {
cout <<
}
int main() {
f();
}
The -nostdinc option successfully avoids including code from standard includes. However, the original #include <iostream> disappears and the namespace specification is repeated.
Is there a way to invoke clang preprocessor to achieve the concatenation described in a straight forward manner?

Answer 1

clang -nostdincdoes another thing, not what you expect. This key disables the standard include directories from the include search paths. So, you get the error since the preprocessor is unable to include the file -nostdinc, could not find it in the known include search paths.
What you want is impossible to achieve. You should use cat your files and clean the result manually or use a special software that can remove #include. I suggest you just use a combinations of grep, sort, uniq and place removed and filtered #include into the top of the concatenated file.