1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1">
<title>The GHC Commentary - Mindboggling Makefiles</title>
</head>
<body BGCOLOR="FFFFFF">
<h1>The GHC Commentary - Mindboggling Makefiles</h1>
<p>
The size and structure of GHC's makefiles makes it quite easy to scream
out loud - in pain - during the process of tracking down problems in the
make system or when attempting to alter it. GHC's <a
href="http://hackage.haskell.org/trac/ghc/wiki/Building">Building
Guide</a> has valuable information on <a
href="http://hackage.haskell.org/trac/ghc/wiki/Building/BuildSystem">the
makefile architecture.</a>
<h4>A maze of twisty little passages, all alike</h4>
<p>
The <code>fptools/</code> toplevel and the various project directories
contain not only a <code>Makefile</code> each, but there are
subdirectories of name <code>mk/</code> at various levels that contain
rules, targets, and so on specific to a project - or, in the case of the
toplevel, the default rules for the whole system. Each <code>mk/</code>
directory contains a file <code>boilerplate.mk</code> that ties the
various other makefiles together. Files called <code>target.mk</code>,
<code>paths.mk</code>, and <code>suffix.mk</code> contain make targets,
definitions of variables containing paths, and suffix rules,
respectively.
<p>
One particularly nasty trick used in this hierarchy of makefiles is the
way in which the variable <code>$(TOP)</code> is used. AFAIK,
<code>$(TOP)</code> always points to a directory containing an
<code>mk/</code> subdirectory; however, it not necessarily points to the
toplevel <code>fptools/</code> directory. For example, within the GHC
subtree, <code>$(TOP)</code> points to <code>fptools/ghc/</code>.
However, some of the makefiles in <code>fptools/ghc/mk/</code> will then
<em>temporarily</em> redefine <code>$(TOP)</code> to point a level
higher (i.e., to <code>fptools/</code>) while they are including the
toplevel boilerplate. After that <code>$(TOP)</code> is redefined to
whatever value it had before including makefiles from higher up in the
hierarchy.
<p><small>
<!-- hhmts start -->
Last modified: Wed Aug 22 16:46:33 GMT Daylight Time 2001
<!-- hhmts end -->
</small>
</body>
</html>
|
