C++ Modules

Modules will be included in C++ 20!


I just tried a small sample on clang-9 and it worked out of the box:


1. Create file test.cppm:


export module M;

export int sum(int op1, int op2)
{
        return op1 + op2;
}


2. Compile the module with:

./clang++ -fmodules-ts --precompile test.cppm --std=c++2a -o M.pcm

./clang++ -fmodules-ts -c M.pcm -o M.o


3. Create file main.cpp:

import M;

#include <iostream>
using namespace std;

int main()
{
        cout << sum(2, 3);

        return 0;
}


4. Compile with:

./clang++ -fmodules-ts -fprebuilt-module-path=. M.o main.cpp -o sample --std=c++2a

5. Run

./sample
5

What a great time to be a C++ programmer. :-)

How to query ElasticSearch using curl

curl -H "Content-Type: application/json" -X POST http://localhost:9200/test2/type1 -d '{ "name": "Marina" }' 


curl -H "Content-Type: application/json" -X GET http://localhost:9200/test2/_search 

Executable sizes

I was curious about the size of executables generated by different compilers in C and C++. So I made a small program that reads a list of numbers from stdin and prints the sum, then compiled it using several compilers and settings. You can find below the results.

Language	Operating system	Compiler	Runtime dependencies	Executable size in bytes
C++	Windows 10	Visual C++ 2017	Dynamic	10,752
C++	Windows 10	Visual C++ 2017	Static	290,816
C	Windows 10	Visual C++ 2017	Dynamic	10,752
C	Windows 10	Visual C++ 2017	Static	140,288
C++	Ubuntu 16.10	GCC 6.2	Dynamic	8,960
C++	Ubuntu 16.10	GCC 6.2	Static	2,202,384
C++	Ubuntu 16.10	GCC 6.2	Static+strip	1,771,096
C	Ubuntu 16.10	GCC 6.2	Dynamic	8,528
C	Ubuntu 16.10	GCC 6.2	Static	915,608
C	Ubuntu 16.10	GCC 6.2	Static+strip	844,784
C++	Ubuntu 16.10	clang 4.0.0	Dynamic	8,984
C++	Ubuntu 16.10	clang 4.0.0	Static	2,202,320
C++	Ubuntu 16.10	clang 4.0.0	Static+strip	1,771,056
C	Ubuntu 16.10	clang 4.0.0	Dynamic	8,352
C	Ubuntu 16.10	clang 4.0.0	Static	915,528
C	Ubuntu 16.10	clang 4.0.0	Static+strip	844,744

The command line used:

clang++ -o main Main.cpp -O3 -static -static-libgcc -static-libstdc++

clang -o main Main.c -O3 -static -static-libgcc

How to static link C and C++ runtimes in gcc 6.2

For C:

gcc -o main Main.c -O2 -static-libgcc -static


For C++:

g++ -o main Main.cpp -O2 -static-libgcc -static-libstdc++ -static


To make sure it worked:


ldd main


should not display any dependencies.

How to dump audio using mplayer

mplayer -dvd-device c:\dvd_pupileira\VIDEO_TS dvd://1 -dumpaudio -dumpfile audio.ac3

How to find development libraries for Ubuntu

Today I was compiling boost in my Ubuntu Linux 14.10 and got the following error:

libs/iostreams/src/bzip2.cpp:20:56: fatal error: bzlib.h: No such file or directory

Then I searched the web and found a nice explanation in this site.

I'll describe below a generic procedure to find which Ubuntu package contains some header file:

1) Install apt-file:

sudo su
apt-get install apt-file
apt-file update

2) Search for packages containing the header file:

apt-file search bzlib.h

3) Install the package:

apt-get install libbz2-dev

Welcome

Hi!

I'm starting this blog to keep track of things that may be useful for me and possibly for others.

My main interests are software development, C++, Formula 1 and racing games / simulators.

I have created another blog for posts in Brazilian Portuguese.

You can contact me through the e-mail cmello @ gmail dot com.
Thank you for the visit!