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
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
<?xml version='1.0'?>
<!--
SPDX-FileCopyrightText: Copyright The SCons Foundation (https://scons.org)
SPDX-License-Identifier: MIT
SPDX-FileType: DOCUMENTATION
This file is processed by the bin/SConsDoc.py module.
-->
<!DOCTYPE sconsdoc [
<!ENTITY % scons SYSTEM "../scons.mod">
%scons;
<!ENTITY % builders-mod SYSTEM "../generated/builders.mod">
%builders-mod;
<!ENTITY % functions-mod SYSTEM "../generated/functions.mod">
%functions-mod;
<!ENTITY % tools-mod SYSTEM "../generated/tools.mod">
%tools-mod;
<!ENTITY % variables-mod SYSTEM "../generated/variables.mod">
%variables-mod;
]>
<section id="sect-parseconfig"
xmlns="http://www.scons.org/dbxsd/v1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.scons.org/dbxsd/v1.0 http://www.scons.org/dbxsd/v1.0/scons.xsd">
<title>Finding Installed Library Information: the &ParseConfig; Function</title>
<para>
Configuring the right options to build programs to work with
libraries--especially shared libraries--that are available
on POSIX systems can be complex.
To help this situation,
various utilities with names that end in <filename>config</filename>
return the command-line options for the GNU Compiler Collection (GCC)
that are needed to build and link against those libraries;
for example, the command-line options
to use a library named <filename>lib</filename>
could be found by calling a utility named <command>lib-config</command>.
</para>
<para>
A more recent convention is that these options
are available through the generic <command>pkg-config</command> program,
providing a common framework, error handling, and the like,
so that all the package creator has to do is provide the set of strings
for his particular package.
</para>
<para>
&SCons; &consenvs; have a &f-link-ParseConfig;
method that asks the host system to execute a command
and then configures the appropriate &consvars; based on
the output of that command.
This lets you run a program like <command>pkg-config</command>
or a more specific utility to help set up your build.
</para>
<scons_example name="parseconfig_ex1">
<file name="SConstruct" printme="1">
env = Environment()
env['CPPPATH'] = ['/lib/compat']
env.ParseConfig("pkg-config x11 --cflags --libs")
print("CPPPATH:", env['CPPPATH'])
</file>
</scons_example>
<para>
&SCons; will execute the specified command string,
parse the resultant flags,
and add the flags to the appropriate environment variables.
</para>
<!--
This is how we used to generate the screen output below, but
as of (at least) Ubuntu Karmic, the pkg-config output for x11
no longer reports back an include directory. Since this is just
for example anyway, we're just hard-coding the output.
<scons_output example="parseconfig_ex1" suffix="1">
<scons_output_command>scons -Q</scons_output_command>
</scons_output>
-->
<screen>
% <userinput>scons -Q</userinput>
CPPPATH: ['/lib/compat', '/usr/X11/include']
scons: `.' is up to date.
</screen>
<para>
In the example above, &SCons; has added the include directory to
&cv-link-CPPPATH;
(depending on what other flags are emitted by the
<filename>pkg-config</filename> command,
other variables may have been extended as well.)
</para>
<para>
Note that the options are merged with existing options using
the &f-link-MergeFlags; method,
so that each option only occurs once in the &consvar;.
</para>
<scons_example name="parseconfig_ex2">
<file name="SConstruct" printme="1">
env = Environment()
env.ParseConfig("pkg-config x11 --cflags --libs")
env.ParseConfig("pkg-config x11 --cflags --libs")
print("CPPPATH:", "CPPPATH:", env['CPPPATH'])
</file>
</scons_example>
<!--
This is how we used to generate the screen output below, but
as of (at least) Ubuntu Karmic, the pkg-config output for x11
no longer reports back an include directory. Since this is just
for example anyway, we're just hard-coding the output.
<scons_output example="parseconfig_ex2" suffix="1">
<scons_output_command>scons -Q</scons_output_command>
</scons_output>
-->
<screen>
% <userinput>scons -Q</userinput>
CPPPATH: ['/usr/X11/include']
scons: `.' is up to date.
</screen>
</section>
|
