Clang error: unknown argument: '-mno-fused-madd' (python package installation failure)

Journey through the solutions

Using environment variables to the rescue

If the clang error is proving to be stubborn, certain configurations prior to your compilation can help. Before installing your package, set up environment variables CFLAGS and CPPFLAGS:

export CFLAGS=-Qunused-arguments    # "Hey clang, ignore args you don't use!"
export CPPFLAGS=-Qunused-arguments  # "This isn't the argument you're looking for."
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Following this, use sudo -E to install the package while retaining these environment variables:

sudo -E pip install <package-name>  # "With the power vested in me by environment variables, I command you to install!"
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Tweaking system files — apply with care!

For Mac users with OS X 10.9 or previous versions, you might need to manually modify a couple of system files, specifically, _sysconfigdata.py. Ensure to tread carefully!

1. Edit _sysconfigdata.py, clearing out any -mno-fused-madd or any other outdated flags.
2. Remove _sysconfigdata.pyc and _sysconfigdata.pyo files. (Your system can bear their absence!)
3. Compile the modified file again using Python:

python -m py_compile _sysconfigdata.py  # "Clean slate, fresh start"
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Compatible clang versions and platforms

Upgrading your Python installation using Homebrew can help avoid these issues, as Homebrew ensures that your install is more recent and stable. Also, don't forget to keep your Xcode version updated if you're on Mavericks 10.9.

Dive deeper — make clang your ally

System permissions for smooth sailing

When modifying system files, you need the root privileges. This ensures that you do not face any permission related hurdles that could halt your progress:

sudo your-command # "Speak 'friend' and enter"
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The power of command line tools

Command line tools such as sed, diff, and patch can aid you immensely in editing and applying changes. Consider them as your essential toolkit for manual edits:

sed 'your expressions' # "Time to cut, join and rearrange"
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Apple's clang got quirks

With the introduction of Apple clang 3.4, be cautious of new defaults like erroring out on unknown flags. This change requires a subtle approach when passing compiler flags.

Espionage in specific scenarios

Particular problems like installing psycopg2 on Mavericks 10.9, might mandate solutions tailored for the context. Manual edits to setup.cfg or other configurations scripts might be necessary.