Deferred Simple Variable Expansion

Most users of GNU make are familiar with its two types of variables: recursive variables, where the value is expanded every time the variable is referenced, and simple variables, where the value is expanded only once: when the variable is assigned. But what if you wanted a variable that was expanded only once, but not until the first time it was used? Such a thing is possible in GNU make… with a bit of trickery.
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Managing Recipe Echoing

Today’s compiler invocations often utilize a large number of flags and options, which can make reading the output from a make invocation difficult. But what’s the best way to provide cleaner build output while still maintaining the ability to see the entire recipe, when necessary?
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Switching GPG keys 

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1,SHA512

I have generated a new 4096-bit RSA GPG key and am switching to it
from my old key.

All future signatures will be created using the new key.  The old key
was not compromised and can continue to be used safely but future
correspondence should be encrypted using the new key.

This document is signed with both keys.

Old key:
pub dsa1024/96B047156338B6D4 2004-01-04
 Key fingerprint = 3D25 54F0 A153 38AB 9AF1  BB9D 96B0 4715 6338 B6D4

New key:
pub rsa4096/80CB727A20C79BB2 2016-10-22
 Key fingerprint = 6D4E EB02 AD83 4703 510B  1176 80CB 727A 20C7 9BB2

Download my new key directly:

  http://mad-scientist.net/gpg/80CB727A20C79BB2.asc

Download my new key using a keyserver:

  gpg --keyserver keys.gnupg.net --recv-key 80CB727A20C79BB2

Display the new fingerprint (compare with the fingerprint above):

  gpg --fingerprint 80CB727A20C79BB2

Display signatures on my new key (it's signed with the old key):

  gpg --check-sigs 80CB727A20C79BB2

To verify this message:

  wget -O- http://mad-scientist.net/gpg/key-transition-2016.asc \
       | gpg --verify

Cheers!

Paul D. Smith <psmith@gnu.org>
Saturday, 22 Oct 2016

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Metaprogramming Make I — Evaluation and Expansion

This is the first in a series of posts discussing metaprogramming techniques in GNU make.

Metaprogramming is the ability of a program generate a program or to modify itself while running. It turns out that GNU make has a number of facilities that can be considered “metaprogramming”, and these capabilities can be incredibly powerful in creating build environments that require a minimal amount of upkeep and maintenance, while providing a significant amount of flexibility. In a series of posts I’ll explore these different facilities, starting from the simplest to most complex.
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