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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8"/>
<title>Build Fundamentals</title>
<meta name="author" content="Sundaram Ramaswamy"/>
<style type="text/css">
.underline { text-decoration: underline; }
</style>
<link rel="stylesheet" href="./reveal.js/dist/reveal.css"/>
<link rel="stylesheet" href="./reveal.js/dist/theme/night.css" id="theme"/>
<link rel="stylesheet" href="./styles.css"/>
<link rel="stylesheet" href="./reveal.js/plugin/highlight/monokai.css"/>
</head>
<body>
<div class="reveal">
<div class="slides">
<section id="sec-title-slide">
<h1 class="title">Build Fundamentals</h1><h2 class="author">Sundaram Ramaswamy</h2><h2 class="email"><a href="mailto:[email protected]">[email protected]</a></h2>
</section>
<section>
<section id="slide-1">
<h2 id="1"><span class="section-number-2">1.</span> Agenda</h2>
<aside class="notes">
<p>
Levels of automation, really.
</p>
</aside>
<form><ol>
<li class="fragment appear">Manual: <b>Hand-made</b>
<form><ul>
<li>Binaries</li>
<li>Build Configurations</li>
</ul></form></li>
<li class="fragment appear">Build system: <b><i>Make</i></b>, <i>Ninja</i>, <i>MSBuild</i>, …
<form><ul>
<li>Targets</li>
<li>Recipes</li>
<li>Dependencies</li>
</ul></form></li>
<li class="fragment appear">Meta-build system: <b><i>GN</i></b>, <i>CMake</i>, <i>meson</i>, …</li>
</ol></form>
</section>
</section>
<section>
<section id="slide-2">
<h2 id="2"><span class="section-number-2">2.</span> Part 1 – <i>Manual</i></h2>
</section>
</section>
<section>
<section id="slide-3">
<h2 id="3"><span class="section-number-2">3.</span> Hand-<del>Make</del> Made</h2>
<div class="org-src-container">
<pre><code class="bash" ># GCC/Clang on Linux/macOS
$ g++ hello.cpp
$ ./a.out
$ g++ -std=c++20 -Wall hello.cpp -o hello
$ ./hello
# MSVC on Windows
> cl /EHsc /std:c++17 /W3 hello.cpp
> hello.exe
</code></pre>
</div>
<form><ul>
<li>Common Flags
<form><ul>
<li>Input: <i>bunch of files</i></li>
<li>Output: <code>-o</code></li>
<li>Language standard: <code>-std=c++14</code> <span class="underline">optional</span></li>
<li>Warning level: <code>-Wall</code> <span class="underline">best practise</span> <span class="underline">optional</span></li>
</ul></form></li>
<li class="fragment appear"><code>g++</code> and <code>cl</code> are just <del>compiler</del> toolchain front-ends
<form><ul>
<li>Clang (<code>clang++</code>) copies GCC’s flags</li>
</ul></form></li>
</ul></form>
<p>
<br />
</p>
<blockquote class="fragment appear">
<p>
A useful <del>wizardry</del> skill even today.
</p>
</blockquote>
</section>
</section>
<section>
<section id="slide-4">
<h2 id="4"><span class="section-number-2">4.</span> Tools in the Chain</h2>
<div class="org-src-container">
<pre><code class="cpp" >#include <iostream> // preprocessor
float perimeter(float radius); // compiler
extern float PI; // linker
int main() { // linker
constexpr auto radius = 2.71828f; // compiler
std::cout << perimeter(radius); // compiler + linker
}
</code></pre>
</div>
<form><ul>
<li>Many tools come together in making a <i>binary</i>
<form><ul>
<li>Preprocessor: glorified find-replace / copy-paste</li>
<li>Compiler: generates code</li>
<li>Linker: resolves dependencies</li>
<li><i>more…</i></li>
</ul></form></li>
<li>Front-end → <i>arguments</i> → Back-end
<form><ul>
<li>Directly or Indirectly</li>
</ul></form></li>
</ul></form>
<p>
<br />
</p>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<colgroup>
<col class="org-left" />
<col class="org-left" />
<col class="org-left" />
</colgroup>
<thead>
<tr>
<th scope="col" class="org-left">Add</th>
<th scope="col" class="org-left">Include Dir (Preprocessor)</th>
<th scope="col" class="org-left">Library Dir (Linker)</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-left">Directly</td>
<td class="org-left"><code>-I./inc</code></td>
<td class="org-left"><code>-L./lib</code></td>
</tr>
<tr>
<td class="org-left">Indirectly</td>
<td class="org-left"><code>-Xpreprocessor -I -Xpreprocessor ./inc</code></td>
<td class="org-left"><code>-Xlinker -L -Xlinker ./lib</code></td>
</tr>
</tbody>
</table>
</section>
</section>
<section>
<section id="slide-5">
<h2 id="5"><span class="section-number-2">5.</span> Binaries</h2>
<form><ul>
<li>Kinds
<form><ol>
<li>Executable</li>
<li>Static Library</li>
<li>Shared Library</li>
</ol></form></li>
<li>Build lingo: <i>artefacts</i></li>
</ul></form>
</section>
</section>
<section>
<section id="slide-6">
<h2 id="6"><span class="section-number-2">6.</span> Object/Machine Code</h2>
<div class="org-src-container">
<pre data-fragment-index="5" class="fragment appear"><code class="bash" >$ g++ -std=c++17 -c hello.cpp
$ ls
hello.cpp hello.o
$ nm hello.o
0000000000000000 T greet
> cl /EHsc /c hello.cpp
> dir
hello.cpp hello.obj
> dumpbin /symbols hello.obj
</code></pre>
</div>
<form><ul>
<li data-fragment-index="1" class="fragment appear">C++ → <del>byte</del> <b>native code</b>; runs on actual CPU
<form><ul>
<li data-fragment-index="2" class="fragment appear">Not interpreted by VM¹
<form><ul>
<li>Java: <i>JVM</i>, Python: <i>CPython</i>, C#: <i>CLR</i>, …</li>
</ul></form></li>
</ul></form></li>
<li data-fragment-index="3" class="fragment appear">Non-portable binary; depends on
<form><ul>
<li>Architecture (arm64, x64, MIPS, PowerPC, …) <span class="underline">EXECUTE</span></li>
<li>OS (Linux, Windows, macOS, …) <span class="underline">LOAD</span> <span class="underline">SYSCALLS</span></li>
</ul></form></li>
<li data-fragment-index="4" class="fragment appear">Basic unit of <i>compiled</i> C, C++ and Obj-C
<form><ul>
<li>GCC/Clang: <code>.o</code></li>
<li>MSVC: <code>.obj</code></li>
</ul></form></li>
</ul></form>
<p data-fragment-index="2" class="fragment appear footnote">
1: Don’t conflate with entire machine VMs like <i>Hyper-V</i>, <i>VirtualBox</i>, …
</p>
</section>
</section>
<section>
<section id="slide-7">
<h2 id="7"><span class="section-number-2">7.</span> Executable</h2>
<div class="org-src-container">
<pre><code class="bash" ># How do I find the OS/architecture of some rogue binary?
# Linux
$ file my_bin
my_bin: ELF 64-bit, x86-64, GNU/Linux 3.2.0, stripped
# macOS
$ file my_bin
my_bin: Mach-O 64-bit executable x86_64
# Windows (MSYS2 or WSL2)
> file my_bin.exe
my_bin.exe: PE32+ executable (console) x86-64, for MS Windows
</code></pre>
</div>
<form><ul>
<li>Linker expects entry point
<form><ul>
<li>C-family standard: <code>int main()</code></li>
<li>OS alternatives e.g. <code>WinMain</code></li>
</ul></form></li>
<li class="fragment appear"><b>Static dependencies resolved early</b> <span class="underline">build</span></li>
<li class="fragment appear"><b>Dynamic dependencies resolved late</b> <span class="underline">run</span></li>
<li class="fragment appear">Dependency Components
<form><ul>
<li>Headers (<code>.h</code>, <code>.hpp</code>, <code>.hxx</code>, …) <span class="underline">compiler</span></li>
<li>Libraries (<code>.a</code>, <code>.lib</code>, <code>.so</code>, <code>.dll</code>, …) <span class="underline">linker</span> <span class="underline">os</span></li>
</ul></form></li>
<li class="fragment appear">Common Dependencies
<form><ul>
<li>System & third-party e.g. <a href="http://www.libpng.org/pub/png/libpng.html">libpng</a> (<code>png.h</code> + <code>libpng.a</code>)</li>
</ul></form></li>
</ul></form>
<p>
<br />
</p>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<colgroup>
<col class="org-left" />
<col class="org-left" />
<col class="org-left" />
</colgroup>
<thead>
<tr>
<th scope="col" class="org-left">OS Family</th>
<th scope="col" class="org-left">Extension</th>
<th scope="col" class="org-left">Format</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-left">Unix</td>
<td class="org-left"><i>none</i></td>
<td class="org-left">Executable & Linkable Format (<a href="https://en.wikipedia.org/wiki/Executable_and_Linkable_Format">ELF</a>)</td>
</tr>
<tr>
<td class="org-left">Windows</td>
<td class="org-left"><code>.exe</code></td>
<td class="org-left">Portable Executable (<a href="https://en.wikipedia.org/wiki/Portable_Executable">PE/PE32+</a>)</td>
</tr>
<tr>
<td class="org-left">macOS</td>
<td class="org-left"><i>none</i></td>
<td class="org-left">Mach object (<a href="https://en.wikipedia.org/wiki/Mach-O">Mach-O</a>)</td>
</tr>
</tbody>
</table>
</section>
</section>
<section>
<section id="slide-8">
<h2 id="8"><span class="section-number-2">8.</span> Static vs Shared Libraries</h2>
<pre class="example" id="org3336745">
+---------------------+----------+ +--------------+ +--------------+
| | | | | | |
| | | | | | |
| Application 1 | Static | | Application | | Application |
| | Lib A | | 3 | | 4 |
| | | | | | |
+---------------------+----------+ +------\-------+ +------/-------+
\ /
\ /
+---------------------+----------+ +----\------------/-----+
| | | | |
| | | | |
| Application 2 | Static | | Shared Library B |
| | Lib A | | |
| | | | |
+---------------------+----------+ +-----------------------+
</pre>
</section>
</section>
<section>
<section id="slide-9">
<h2 id="9"><span class="section-number-2">9.</span> Static Library</h2>
<div class="org-src-container">
<pre><code class="bash" data-line-numbers='1,2,4,13-15'>$ ar -rcs libTrig.a sin.o cos.o tan.o
$ ar -t libTrig.a
sin.o cos.o tan.o
$ nm libTrig.a
0000000000000000 T sin
0000000000001000 T cos
$ ls -l
80K libTrig.a
20K libmath.a
200K tool.o
$ gcc -o tool tool.o libTrig.a
ld: sin.o: undefined reference to 'add(int, int)'
$ gcc -o tool tool.o -ltrig -lmath
$ ls -l tool
300K tool
</code></pre>
</div>
<form><ul>
<li class="fragment appear">An archive of object files <span class="underline">linker</span>
<form><ul>
<li>With interface headers e.g. <code>trig.h</code> <span class="underline">compiler</span></li>
</ul></form></li>
<li class="fragment appear"><b>Code attached to final executable</b> <span class="underline">build</span>
<form><ul>
<li>Static/Compile-time linking by linker</li>
</ul></form></li>
<li class="fragment appear"><b>Dependencies aren’t resolved!</b> <span class="underline">build</span>
<form><ul>
<li>Final binary to supply dependency</li>
</ul></form></li>
<li class="fragment appear">Toolchain feature; OS uninvolved</li>
<li class="fragment appear">No entry functions <code>main()</code>, <code>DllMain()</code>, …</li>
</ul></form>
</section>
<section id="slide-9-1">
<h3 id="9-1"><span class="section-number-3">9.1.</span> Pros & Cons</h3>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<colgroup>
<col class="org-left" />
<col class="org-left" />
</colgroup>
<tbody>
<tr>
<td class="org-left">No “missing dependencies” error for app</td>
<td class="org-left">No sweeping updates / fixes</td>
</tr>
<tr>
<td class="org-left">No version mismatches or <a href="https://en.wikipedia.org/wiki/Dependency_hell">Dependency Hell</a></td>
<td class="org-left">Every app to rebuild on update</td>
</tr>
<tr>
<td class="org-left">Single executable; simpler package/install</td>
<td class="org-left">Disk space (fat binaries, multiple copies)¹</td>
</tr>
<tr>
<td class="org-left">Apps may ignore breaking lib version</td>
<td class="org-left">No on-demand loading / plug-ins</td>
</tr>
<tr>
<td class="org-left">Library needn’t be backward-compatible</td>
<td class="org-left">Slower build time for app (strip unused)</td>
</tr>
</tbody>
</table>
<p style="font-size: large;">
1: Doesn’t apply to <i>Windows</i>; each software brings its own (non-system) libraries
</p>
</section>
</section>
<section>
<section id="slide-10">
<h2 id="10"><span class="section-number-2">10.</span> Shared/Dynamic Library</h2>
<div class="org-src-container">
<pre><code class="bash" data-line-numbers='1,6,12'>$ g++ -o tool tool.o
$ ls -l
200K tool.o
200K tool
$ g++ -shared -fPIC {sin,cos,tan}.cpp -o trig.dll -lmath
$ nm trig.dll
0000000000000000 T sin
0000000000001000 T cos ...
$ gcc -o tool tool.o trig.dll
$ ls -l
80K trig.dll
200K tool.o
200K tool
</code></pre>
</div>
<form><ul>
<li class="fragment appear">Single library shared across apps <span class="underline">run</span>
<form><ul>
<li>Single copy in memory at runtime</li>
</ul></form></li>
<li class="fragment appear"><b>Static dependencies resolved</b> <span class="underline">build</span>
<form><ul>
<li>Need dynamic dependencies at launch</li>
<li><code>a.dll</code> → <code>b.dll</code> → … 😲 <span class="underline">dependency chain</span></li>
</ul></form></li>
<li class="fragment appear"><b>Final executable contains <del>code</del> only jumps</b></li>
<li class="fragment appear">Dynamic/run-time linking by OS/loader <span class="underline">run</span>
<form><ul>
<li>Expects library presence in right path on
<form><ul>
<li>Launch</li>
<li>Demand: <code>dlopen</code>, <code>LoadLibrary</code></li>
</ul></form></li>
</ul></form></li>
<li class="fragment appear">Entry functions e.g. <code>DllMain</code></li>
</ul></form>
<p>
<br />
</p>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<colgroup>
<col class="org-left" />
<col class="org-left" />
</colgroup>
<thead>
<tr>
<th scope="col" class="org-left">OS</th>
<th scope="col" class="org-left">Name</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-left">Windows</td>
<td class="org-left">Dynamic Link Libraries (<code>.dll</code>)</td>
</tr>
<tr>
<td class="org-left">Linux</td>
<td class="org-left">Shared Objects (<code>.so</code>)</td>
</tr>
<tr>
<td class="org-left">macOS</td>
<td class="org-left">Dynamic Shared Libraries/Bundles (<code>.dylib</code> / <code>.so</code>)</td>
</tr>
</tbody>
</table>
</section>
<section id="slide-10-1">
<h3 id="10-1"><span class="section-number-3">10.1.</span> Pros & Cons</h3>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<colgroup>
<col class="org-left" />
<col class="org-left" />
</colgroup>
<tbody>
<tr>
<td class="org-left">Sweeping updates / fixes</td>
<td class="org-left">Missing dependencies; failure to launch</td>
</tr>
<tr>
<td class="org-left">Plug-ins / on-demand loads</td>
<td class="org-left">Versioning / Dependency Hell</td>
</tr>
<tr>
<td class="org-left">Toolchain independent; cross-toolchain</td>
<td class="org-left">OS dependent</td>
</tr>
<tr>
<td class="org-left">No app rebuilding</td>
<td class="org-left">Many OS-specific binaries; pkg/install hassle</td>
</tr>
<tr>
<td class="org-left">Lesser disk footprint</td>
<td class="org-left">Backward-compatible considerations</td>
</tr>
<tr>
<td class="org-left"> </td>
<td class="org-left">Forced updates breaking app</td>
</tr>
</tbody>
</table>
</section>
</section>
<section>
<section id="slide-11">
<h2 id="11"><span class="section-number-2">11.</span> Tools and Switches</h2>
<div class="org-src-container">
<pre><code class="bash" ># GCC/MinGW on Windows
> g++ -std=c++17 -D_DEBUG hello.cpp -g -O0 -flto -o hello.exe
# MSVC on Windows
> cl /EHsc /std:c++17 /D_DEBUG hello.cpp /Zi /Od /LTCG
</code></pre>
</div>
<form><ul>
<li class="fragment appear">Compiler Flags
<form><ul>
<li>Enable debug symbols: <code>-g</code></li>
<li>Disable optimizations: <code>-O0</code></li>
</ul></form></li>
<li class="fragment appear">Linker Flags
<form><ul>
<li>Link time optimization: <code>-flto</code></li>
</ul></form></li>
<li class="fragment appear">Preprocessor Flags
<form><ul>
<li>Define macros, add include dirs, etc.</li>
<li><code>-D_DEBUG</code> → <code>#define _DEBUG</code></li>
<li><code>-DPI=3.14</code> → <code>#define PI 3.14</code></li>
</ul></form></li>
<li class="fragment appear"><b>List of flags can get long, <i>really long</i></b>
<form><ul>
<li>MSVC: 166 (<i>1 platform, arch-neutral</i>)</li>
<li>GCC: <a href="https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Option-Summary.html">gazillion</a> (<i>multi-arch, multi-platform</i> 🤯)</li>
</ul></form></li>
</ul></form>
</section>
</section>
<section>
<section id="slide-12">
<h2 id="12"><span class="section-number-2">12.</span> Software and Features</h2>
<blockquote>
<p>
Conditional compilation of certain pieces of code.
</p>
</blockquote>
<div class="org-src-container">
<pre><code class="bash" ># 2. Conditional Inclusion
# BUILD.gn
if (is_linux || is_chromeos) {
sources += [
"base_paths_posix.cc"
]
}
</code></pre>
</div>
<div class="org-src-container">
<pre><code class="cpp" >// 1. Macro
// C++
#if defined(ENABLE_TAB_TOGGLE)
tab_toggler.init();
#endif
</code></pre>
</div>
<form><ul>
<li>Features are made of code</li>
<li>Code can guarded by switches
<form><ol>
<li>Macros</li>
<li>Conditional inclusion of files</li>
</ol></form></li>
<li class="fragment appear"><b>Binary won’t have omitted feature’s bits</b>
<form><ul>
<li>Unlike <i>command-line-flag</i>-enabled features</li>
</ul></form></li>
</ul></form>
</section>
</section>
<section>
<section id="slide-13">
<h2 id="13"><span class="section-number-2">13.</span> Build Configuration</h2>
<blockquote>
<p>
<b>Configuration</b>: particular combination of all switches¹.
</p>
</blockquote>
<form><ul>
<li class="fragment appear">Theoretically <code>m × n</code> switches (<i>toolchain × software</i>)
<form><ul>
<li>Strictly speaking <code>m x n</code> isn’t possible</li>
</ul></form></li>
<li class="fragment appear"><b>Switches can be inter-dependant</b>
<form><ul>
<li>Example: turning on PDF might need Print support</li>
<li>Example: turning on logging for <i>Debug</i> builds</li>
</ul></form></li>
<li class="fragment appear">Manual: tedious and error-prone
<form><ul>
<li>Hampers reproducibility, productivity and maintenance</li>
</ul></form></li>
</ul></form>
<p>
<br />
</p>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<colgroup>
<col class="org-left" />
<col class="org-left" />
<col class="org-left" />
<col class="org-left" />
<col class="org-left" />
<col class="org-left" />
<col class="org-left" />
</colgroup>
<thead>
<tr>
<th scope="col" class="org-left"> </th>
<th scope="col" class="org-left">Emojis</th>
<th scope="col" class="org-left">Speech</th>
<th scope="col" class="org-left">Plugins</th>
<th scope="col" class="org-left">Logging</th>
<th scope="col" class="org-left">Debug</th>
<th scope="col" class="org-left">Optimization</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-left">Config1</td>
<td class="org-left">✓</td>
<td class="org-left">✓</td>
<td class="org-left">✓</td>
<td class="org-left"> </td>
<td class="org-left"> </td>
<td class="org-left">✓</td>
</tr>
<tr>
<td class="org-left">Config2</td>
<td class="org-left"> </td>
<td class="org-left"> </td>
<td class="org-left">✓</td>
<td class="org-left">✓</td>
<td class="org-left">✓</td>
<td class="org-left"> </td>
</tr>
</tbody>
</table>
<p class="footnote">
1: Think: <code>args.gn</code>
</p>
</section>
</section>
<section>
<section id="slide-14">
<h2 id="14"><span class="section-number-2">14.</span> Common Configurations</h2>
<div class="org-src-container">
<pre><code class="bash" >$ cd ~/edge/src
$ gn args out/release_x64 --list --short | wc -l
887
$ wc -l < out/release_x64/args.gn
11
$ gn args out/release_x64 --list --short --overrides-only | wc -l
20
$ gn args out/release_x64 --list=crashpad_dependencies
crashpad_dependencies
Current value = "chromium"
From //.gn:51
Overridden from the default = "standalone"
From //third_party/crashpad/crashpad/build/crashpad_buildconfig.gni:19
</code></pre>
</div>
<form><ul>
<li><i>Debug</i>
<form><ul>
<li>Disable optimizations</li>
<li>Keep symbols</li>
</ul></form></li>
<li><i>Release</i>
<form><ul>
<li>Enable optimizations</li>
<li>Strip debug symbols</li>
</ul></form></li>
<li>Debug − logging (<i>DbgNoLog</i>)</li>
<li>Release + debug (<i>RelDbg</i>)</li>
<li>Release + size optimization (<i>RelMinSize</i>)</li>
<li>…</li>
</ul></form>
</section>
</section>
<section>
<section id="slide-15">
<h2 id="15"><span class="section-number-2">15.</span> Part 2 – Build System</h2>
</section>
</section>
<section>
<section id="slide-16">
<h2 id="16"><span class="section-number-2">16.</span> Make</h2>
<form><ul>
<li class="fragment appear">First step towards build automation</li>
<li class="fragment appear">Minimal enough to learn important build concepts</li>
<li class="fragment appear">Powerful enough; still used in production code
<form><ul>
<li>Good for quick workouts personally</li>
</ul></form></li>
<li class="fragment appear">Cross-platform, cross-toolchain POSIX standard <span class="underline">productivity</span>
<form><ul>
<li>GCC/Clang: GNU <code>make</code>, BSD <code>make</code>; MSVC: <code>nmake</code></li>
<li>Most IDEs support Makefile-based projects</li>
<li>VS 2019+: UNIX makefile project template</li>
</ul></form></li>
<li class="fragment appear">Rebuild only changed parts <span class="underline">speed</span> <span class="underline">dry</span>
<form><ul>
<li>Avoids hand-compiling tedium and mistakes</li>
<li>Enables build reproducibility in a team</li>
</ul></form></li>
</ul></form>
</section>
</section>
<section>
<section id="slide-17">
<h2 id="17"><span class="section-number-2">17.</span> Makefile Rules 🤘</h2>
<div class="org-src-container">
<pre><code class="makefile" ># commonly used flags in variable
CXXFLAGS = -std=c++17 -Wall
LDFLAGS = -flto
biryani: rice.o spices.o
g++ $(LDFLAGS) -o biryani rice.o spices.o
cp biryani ./installer/bin
spices.o: spices.cpp spices.h
g++ $(CXXFLAGS) -o spices.o -c spices.cpp
rice.o: rice.cpp rice.h utensils.h spices.h
g++ $(CXXFLAGS) -o rice.o -c rice.cpp
clean:
rm -rf biryani *.o
.PHONY: clean
</code></pre>
</div>
<form><ul>
<li>Add <code>Makefile</code> at project root with <i>rules</i></li>
<li class="fragment appear"><b>Target</b>: final artefact expected
<form><ul>
<li>Considered outdated if older than a dependency</li>
</ul></form></li>
<li class="fragment appear"><b>Dependency</b>: ingredients needed to make target</li>
<li class="fragment appear"><b>Recipe</b>: snippet making target from dependencies
<form><ul>
<li>Target <i>outdated</i> ¹? Re-run recipe!</li>
</ul></form></li>
<li class="fragment appear"><code>make</code>: build first target
<form><ul>
<li><code>make TARGET</code>: only build <code>TARGET</code> (and its dependencies)</li>
</ul></form></li>
<li class="fragment appear"><i>Golden Rule</i>
<form><ul>
<li><i>Every target’s recipe should update file naming it.</i></li>
<li>Add exceptions to <code>.PHONY</code>; always outdated</li>
</ul></form></li>
</ul></form>
<p class="footnote">
1: older than a dependency
</p>
</section>
</section>
<section>
<section id="slide-18">
<h2 id="18"><span class="section-number-2">18.</span> Makefile Refinements</h2>
<div class="org-src-container">
<pre><code class="makefile" ># commonly used flags in variable
CXXFLAGS = $(USERFLAGS) -std=c++17 -Wall
LDFLAGS = -flto # LTO ON
LDLIBS = -lz -lmath # libMath.a, libZ.a
biryani: rice.o spices.o
$(CC) $(LDFLAGS) -o $@ $^ $(LDLIBS)
cp biryani ./installer/bin
spices.o: spices.cpp spices.h
rice.o: rice.cpp rice.h utensils.h spices.h
doc: ref.html tutorial.html
# Pattern rule
%.html: %.md
pandoc -o $@ $<
# e.g. pandoc -o ref.html ref.md
clean:
$(RM) biryani *.o
commit:
git add $(wildcard *.cpp *.h)
git commit
.PHONY: clean doc commit
</code></pre>
</div>
<form><ul>
<li>Power to build engineers
<form><ul>
<li>Override settings without editing <code>Makefile</code></li>
<li><code>make CC=clang++</code>: override toolchain to Clang</li>
<li><code>USER_FLAGS='-DMY_SHINY_FEATURE=ON -O3' make</code></li>
</ul></form></li>
<li class="fragment appear">Special variables
<form><ul>
<li>target <code>$@</code>, dependencies <code>$^</code>, first dep: <code>$<</code></li>
</ul></form></li>
<li class="fragment appear">Pattern rule: map <code>.X</code> → <code>.Y</code></li>
<li class="fragment appear">Make <i>knows</i> how to build <code>.o</code> from <code>.cpp</code>, <code>.c</code>, etc.
<form><ul>
<li>Implicit rule: <code>$(CC) -c $(CFLAGS) -o $@ $<</code></li>
</ul></form></li>
<li class="fragment appear">Make isn’t language-specific
<form><ul>
<li><code>make doc</code> builds documentation using <a href="https://pandoc.org/">Pandoc</a></li>
<li><code>make install</code>: bunch of copies</li>
</ul></form></li>
</ul></form>
</section>
</section>
<section>
<section id="slide-19">
<h2 id="19"><span class="section-number-2">19.</span> Makefile Builds</h2>
<div class="org-src-container">
<pre><code class="makefile" >.POSIX:
COMPILER_FLAGS = -Wall -Werror -pedantic -pedantic-errors
CXXFLAGS = -std=c++17 $(COMPILER_FLAGS)
all: debug release
debug: CXXFLAGS += -g -O0 -D_DEBUG -DDEBUG
debug: hello
release: CXXFLAGS += -O2 -DNDEBUG
release: hello
hello: hello.swift MyCMod/adder.o
swiftc -I . -o $@ $<
MyCMod/adder.o: MyCMod/adder.cpp MyCMod/adder.h
clean:
$(RM) hello MyCMod/adder.o
.PHONY: all clean
</code></pre>
</div>
<form><ul>
<li>Separate debug and release targets</li>
<li>Per-target variable values</li>
<li><code>make debug</code> and <code>make release</code></li>
<li><code>make</code> to build both
<form><ul>
<li>Convention: Make an <code>all</code> target</li>
</ul></form></li>