summaryrefslogtreecommitdiffstats
path: root/doc/user/parseflags.xml
blob: 632077e5f141e4febd9621a23291557219b88c44 (plain)
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
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
<!--

  __COPYRIGHT__

  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:

  The above copyright notice and this permission notice shall be included
  in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
  KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

-->

 <para>

 &SCons; has a bewildering array of construction variables
 for different types of options when building programs.
 Sometimes you may not know exactly which variable
 should be used for a particular option.

 </para>

 <para>

 &SCons; construction environments have a &ParseFlags; method
 that takes a set of typical command-line options
 and distrbutes them into the appropriate construction variables.
 Historically, it was created to support the &ParseConfig; method,
 so it focuses on options used by the GNU Compiler Collection (GCC)
 for the C and C++ toolchains.

 </para>

 <para>

 &ParseFlags; returns a dictionary containing the options
 distributed into their respective construction variables.
 Normally, this dictionary would be passed to &MergeFlags;
 to merge the options into a &consenv;,
 but the dictionary can be edited if desired to provide
 additional functionality.
 (Note that if the flags are not going to be edited,
 calling &MergeFlags; with the options directly
 will avoid an additional step.)

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags("-I/opt/include -L/opt/lib -lfoo")
    l = d.items()
    l.sort()
    for k,v in l:
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cc -o f1.o -c -I/opt/include f1.c
    cc -o f1 f1.o -L/opt/lib -lfoo
 </screen>

 <para>

 Note that if the options are limited to generic types
 like those above,
 they will be correctly translated for other platform types:

 </para>

 <screen>
    C:\><userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cl /Fof1.obj /c f1.c /nologo /I\opt\include
    link /nologo /OUT:f1.exe /LIBPATH:\opt\lib foo.lib f1.obj
 </screen>

 <para>

 Since the assumption is that the flags are used for the GCC toolchain,
 unrecognized flags are placed in &cv-link-CCFLAGS;
 so they will be used for both C and C++ compiles:

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags("-whatever")
    l = d.items()
    l.sort()
    for k,v in l:
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CCFLAGS -whatever
    cc -o f1.o -c -whatever f1.c
    cc -o f1 f1.o
 </screen>

 <para>

 &ParseFlags; will also accept a (recursive) list of strings as input;
 the list is flattened before the strings are processed:

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags(["-I/opt/include", ["-L/opt/lib", "-lfoo"]])
    l = d.items()
    l.sort()
    for k,v in l:
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cc -o f1.o -c -I/opt/include f1.c
    cc -o f1 f1.o -L/opt/lib -lfoo
 </screen>

 <para>

 If a string begins with a "!" (an exclamation mark, often called a bang),
 the string is passed to the shell for execution.
 The output of the command is then parsed:

 </para>

 <programlisting>
    env = Environment()
    d = env.ParseFlags(["!echo -I/opt/include", "!echo -L/opt/lib", "-lfoo"])
    l = d.items()
    l.sort()
    for k,v in l:
        if v:
            print k, v
    env.MergeFlags(d)
    env.Program('f1.c')
 </programlisting>

 <screen>
    % <userinput>scons -Q</userinput>
    CPPPATH ['/opt/include']
    LIBPATH ['/opt/lib']
    LIBS ['foo']
    cc -o f1.o -c -I/opt/include f1.c
    cc -o f1 f1.o -L/opt/lib -lfoo
 </screen>

 <para>

 &ParseFlags; is regularly updated for new options;
 consult the man page for details about those currently recognized.

 </para>