---
slug: "mac-clang-error-unknownargument-mno-fused-madd-ARCHFLAGS"
title: "On a Mac, encountering clang: error: unknown argument: '-mno-fused-madd' → Use ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future"
description: "\n$ pip install reportlab\n\nAfter running this command"
url: "https://www.ytyng.com/en/blog/mac-clang-error-unknownargument-mno-fused-madd-ARCHFLAGS"
publish_date: "2014-04-27T09:53:28Z"
created: "2014-04-27T09:53:28Z"
updated: "2026-02-26T22:00:34.864Z"
categories: ["mac"]
keywords: ""
featured_image_url: "https://media.ytyng.com/resize/20230812/92ee1dca6a62445ab76d487dbe9fe7c3.png.webp?width=768"
has_video: false
has_music: false
video_urls: []
music_urls: []
lang: "en"
---

# On a Mac, encountering clang: error: unknown argument: '-mno-fused-madd' → Use ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future

<div class="document">
<pre class="literal-block">$ pip install reportlab
</pre>
<p>After running this command</p>
<pre class="literal-block">clang: error: unknown argument: '-mno-fused-madd' [-Wunused-command-line-argument-hard-error-in-future]

clang: note: this will be a hard error (cannot be downgraded to a warning) in the future

error: command 'cc' failed with exit status 1
</pre>
<p>I encountered this error.</p>
<p>It seems to occur during the installation of a dependency package (pillow?).</p>
<p>Fix 'clang: unknown argument' error after updating to Xcode 5.1</p>
<p><a class="reference external" href="http://kaspermunck.github.io/2014/03/fixing-clang-error/">http://kaspermunck.github.io/2014/03/fixing-clang-error/</a></p>
<p>Referring to this page</p>
<pre class="literal-block">ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future pip install reportlab
</pre>
</div>