Basics: Boilerplate, And Executables

Single Monolithic Executable

See also

• Toolchain: Basics

Source

01-single/
├── CMakeLists.txt
└── hello-single.c

• 01-single/CMakeLists.txt

• 01-single/hello-single.c

• Toolchain: Basics

• Default output name: a.out

  $ gcc hello-single.c
  $ ./a.out
  Hello World
  

• Explicit output name

  $ gcc -o hello-single hello-single.c
  $ ./hello-single
  Hello World
  

• Wish list item: out-of-source build (Git requires me to .gitignore output files, for example)

• ⟶ CMake

Building With CMake

Documentation

• CMAKE_MINIMUM_REQUIRED()

• PROJECT()

• ADD_EXECUTABLE()

• CMakeLists.txt (top-level, others will follow once we have subdirectories)

  01-single/CMakeLists.txt

  CMAKE_MINIMUM_REQUIRED(VERSION 3.16)
  PROJECT(Demo)
  ADD_EXECUTABLE(hello-single hello-single.c)
  

• CMAKE_MINIMUM_REQUIRED(): required by CMake; used to declare which features we will need (or fail)

• PROJECT(): used in many corners, e.g. package names

  • VERSION parameter (optional); will use it later

• ADD_EXECUTABLE()

Building With CMake: Separate Source And Build Directories

• Source directory, e.g. ~/My-Projects/01-single

  • Version controlled

• Build directory, e.g. ~/My-Builds/01-single-x86_64

  • Not version controlled ⟶ does not interfere with version control (no need to .gitignore build directory)

  • Completely resurrectable

  • Not subject to backups

  • Cheap storage medium

• Simplest way of building

  • Change to build directory

  • Call cmake to build Makefile skeleton (or ninja) from the source directory

  • Call make (or ninja, for that matter) in the build directory

Create Makefile structure

$ cd ~/My-Builds/01-single-x86_64
$ cmake ~/My-Projects/01-single
-- The C compiler identification is GNU 12.2.1
-- The CXX compiler identification is GNU 12.2.1
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.7s)
-- Generating done (0.0s)
-- Build files have been written to: /home/jfasch/My-Builds/01-single-x86_64

Build using make

$ make
[ 50%] Building C object CMakeFiles/hello-single.dir/hello-single.c.o
[100%] Linking C executable hello-single
[100%] Built target hello-single

Executables Consisting Of Multiple Sources

Source

02-modular/
├── CMakeLists.txt
├── hello.c
├── hello.h
└── hello-main.c

• 02-modular/CMakeLists.txt

• 02-modular/hello-main.c

• 02-modular/hello.h

• 02-modular/hello.c

• Programs are rarely so simple

• Separate compilation units

• ⟶ potential code re-use

• ADD_EXECUTABLE() can take more than one source file parameters

ADD_EXECUTABLE(hello-modular hello-main.c hello.c)

Problem: Duplicate Compilation

Source

03-two-users-duplicate-compilation/
├── CMakeLists.txt
├── hello.c
├── hello-first.c
├── hello.h
└── hello-second.c

• 03-two-users-duplicate-compilation/CMakeLists.txt

• 03-two-users-duplicate-compilation/hello-first.c

• 03-two-users-duplicate-compilation/hello-second.c

• 03-two-users-duplicate-compilation/hello.h

• 03-two-users-duplicate-compilation/hello.c

• Maybe show raw toolchain in action: Zooming In: Separate Compilation, and Linking Statically

• Duplication of build rules (hello.c is built twice)

  ADD_EXECUTABLE(hello-first hello-first.c hello.c)
  ADD_EXECUTABLE(hello-second hello-second.c hello.c)
  

Problem: More Functionality

Source

04-more-functionality/
├── CMakeLists.txt
├── hello.c
├── hello-first.c
├── hello.h
├── hello-name.c
├── hello-name.h
└── hello-second.c

• 04-more-functionality/CMakeLists.txt

• 04-more-functionality/hello-first.c

• 04-more-functionality/hello-second.c

• 04-more-functionality/hello.h

• 04-more-functionality/hello.c

• 04-more-functionality/hello-name.c

• 04-more-functionality/hello-name.h

• Download hello-name.{h,c} (add new function hello_name())

• Call in both executables. Live-hack commandline args.

  • hello-first takes only argv[1]

  • hello-second is more elaborate: all the rest

04-more-functionality/hello-name.h

#ifndef HELLO_NAME_H
#define HELLO_NAME_H

void hello_name(const char* name);

#endif

04-more-functionality/hello-name.c

#include "hello-name.h"
#include <stdio.h>

void hello_name(const char* name)
{
    printf("Hello %s\n", name);
}

Solution: Libraries

• Bag of object files

• Come in static and shared flavors