blame: source/misc/embedded_libs/fmt-11.0.2/doc/index.md

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# A modern formatting library

<div class="features-container">

<div class="feature">

<h2>Safety</h2>

<p>

  Inspired by Python's formatting facility, {fmt} provides a safe replacement

  for the <code>printf</code> family of functions. Errors in format strings,

  which are a common source of vulnerabilities in C, are <b>reported at

  compile time</b>. For example:

  <pre><code class="language-cpp"

  >fmt::format("{:d}", "I am not a number");</code></pre>

  will give a compile-time error because <code>d</code> is not a valid

  format specifier for strings. APIs like <a href="api/#format">

  <code>fmt::format</code></a> <b>prevent buffer overflow errors</b> via

  automatic memory management.

</p>

<a href="api#compile-time-checks">→ Learn more</a>

</div>

<div class="feature">

<h2>Extensibility</h2>

<p>

  Formatting of most <b>standard types</b>, including all containers, dates,

  and times is <b>supported out-of-the-box</b>. For example:

  <pre><code class="language-cpp"

  >fmt::print("{}", std::vector{1, 2, 3});</code></pre>

  prints the vector in a JSON-like format:

  <pre><code>[1, 2, 3]</code></pre>

  You can <b>make your own types formattable</b> and even make compile-time

  checks work for them.

</p>

<a href="api#udt">→ Learn more</a>

</div>

<div class="feature">

<h2>Performance</h2>

<p>

  {fmt} can be anywhere from <b>tens of percent to 20-30 times faster</b> than

  iostreams and <code>sprintf</code>, especially for numeric formatting.

<a href="https://github.com/fmtlib/fmt?tab=readme-ov-file#benchmarks">

<img src="perf.svg">

</a>

  The library <b>minimizes dynamic memory allocations</b> and can optionally

  <a href="api#compile-api">compile format strings</a> to optimal code.

</p>

</div>

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<h2>Unicode support</h2>

<p>

  {fmt} provides <b>portable Unicode support</b> on major operating systems

  with UTF-8 and <code>char</code> strings. For example:

  <pre><code class="language-cpp"

  >fmt::print("Слава Україні!");</code></pre>

  will be printed correctly on Linux, macOS, and even Windows console,

  irrespective of the codepages.

</p>

<p>

  The default is <b>locale-independent</b>, but you can opt into localized

  formatting and {fmt} makes it work with Unicode, addressing issues in the

  standard libary.

</p>

</div>

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<h2>Fast compilation</h2>

<p>

  The library makes extensive use of <b>type erasure</b> to achieve fast

  compilation. <code>fmt/base.h</code> provides a subset of the API with

  <b>minimal include dependencies</b> and enough functionality to replace

  all uses of <code>*printf</code>.

</p>

<p>

  Code using {fmt} is usually several times faster to compile than the

  equivalent iostreams code, and while <code>printf</code> compiles faster

  still, the gap is narrowing.

</p>

<a href=

"https://github.com/fmtlib/fmt?tab=readme-ov-file#compile-time-and-code-bloat">

→ Learn more</a>

</div>

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<h2>Small binary footprint</h2>

<p>

  Type erasure is also used to prevent template bloat, resulting in <b>compact

  per-call binary code</b>. For example, a call to <code>fmt::print</code> with

  a single argument is just <a href="https://godbolt.org/g/TZU4KF">a few

  instructions</a>, comparable to <code>printf</code> despite adding

  runtime safety, and much smaller than the equivalent iostreams code.

</p>

<p>

  The library itself has small binary footprint and some components such as

  floating-point formatting can be disabled to make it even smaller for

  resource-constrained devices.

</p>

</div>

<div class="feature">

<h2>Portability</h2>

<p>

  {fmt} has a <b>small self-contained codebase</b> with the core consisting of

  just three headers and no external dependencies.

</p>

<p>

  The library is highly portable and requires only a minimal <b>subset of

  C++11</b> features which are available in GCC 4.8, Clang 3.4, MSVC 19.0

  (2015) and later. Newer compiler and standard library features are used

  if available, and enable additional functionality.

</p>

<p>

  Where possible, the output of formatting functions is <b>consistent across

  platforms</b>.

</p>

</p>

</div>

<div class="feature">

<h2>Open source</h2>

<p>

  {fmt} is in the top hundred open-source C++ libraries on GitHub and has

  <a href="https://github.com/fmtlib/fmt/graphs/contributors">hundreds of

  all-time contributors</a>.

</p>

<p>

  The library is distributed under a permissive MIT

  <a href="https://github.com/fmtlib/fmt#license">license</a> and is

  <b>relied upon by many open-source projects</b>, including Blender, PyTorch,

  Apple's FoundationDB, Windows Terminal, MongoDB, and others.

</p>

</div>

</div>