summaryrefslogtreecommitdiffstats
path: root/doc/user/less-simple.in
blob: 23b585c2456d7f189f7ca9c6e8651307dccb6be4 (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
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
<!--

  __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>

  In this chapter,
  you will see several examples of
  very simple build configurations using &SCons;,
  which will demonstrate how easy
  it is to use &SCons; to
  build programs from several different programming languages
  on different types of systems.

  </para>

  <section>
  <title>Specifying the Name of the Target (Output) File</title>

    <para>

    You've seen that when you call the &b-link-Program; builder method,
    it builds the resulting program with the same
    base name as the source file.
    That is, the following call to build an
    executable program from the &hello_c; source file
    will build an executable program named &hello; on POSIX systems,
    and an executable program named &hello_exe; on Windows systems:

    </para>

    <programlisting>
       Program('hello.c')
    </programlisting>

    <para>

    If you want to build a program with
    a different name than the base of the source file name,
    you simply put the target file name
    to the left of the source file name:

    </para>

    <scons_example name="target">
       <file name="SConstruct" printme="1">
       Program('new_hello', 'hello.c')
       </file>
       <file name="hello.c">
       int main() { printf("Hello, world!\n"); }
       </file>
    </scons_example>

    <para>

    (&SCons; requires the target file name first,
    followed by the source file name,
    so that the order mimics that of an
    assignment statement in most programming languages,
    including Python:
    <literal>"program = source files"</literal>.)

    </para>

    <para>

    Now &SCons; will build an executable program
    named &new_hello; when run on a POSIX system:

    </para>

    <scons_output example="target" os="posix">
       <scons_output_command>scons -Q</scons_output_command>
    </scons_output>

    <para>

    And &SCons; will build an executable program
    named &new_hello_exe; when run on a Windows system:

    </para>

    <scons_output example="target" os="win32">
       <scons_output_command>scons -Q</scons_output_command>
    </scons_output>

  </section>

  <section>
  <title>Compiling Multiple Source Files</title>

    <para>

    You've just seen how to configure &SCons;
    to compile a program from a single source file.
    It's more common, of course,
    that you'll need to build a program from
    many input source files, not just one.
    To do this, you need to put the
    source files in a Python list
    (enclosed in square brackets),
    like so:

    </para>

    <scons_example name="ex2">
       <file name="SConstruct" printme="1">
       Program(['prog.c', 'file1.c', 'file2.c'])
       </file>
       <file name="prog.c">
       int main() { printf("prog.c\n"); }
       </file>
       <file name="file1.c">
       void file1() { printf("file1.c\n"); }
       </file>
       <file name="file2.c">
       void file2() { printf("file2.c\n"); }
       </file>
    </scons_example>

    <para>

    A build of the above example would look like:

    </para>

    <scons_output example="ex2">
       <scons_output_command>scons -Q</scons_output_command>
    </scons_output>

    <para>

    Notice that &SCons;
    deduces the output program name
    from the first source file specified
    in the list--that is,
    because the first source file was &prog_c;,
    &SCons; will name the resulting program &prog;
    (or &prog_exe; on a Windows system).
    If you want to specify a different program name,
    then (as we've seen in the previous section)
    you slide the list of source files
    over to the right
    to make room for the output program file name.
    (&SCons; puts the output file name to the left
    of the source file names
    so that the order mimics that of an
    assignment statement:  "program = source files".)
    This makes our example:

    </para>

    <scons_example name="ex3">
       <file name="SConstruct" printme="1">
       Program('program', ['prog.c', 'file1.c', 'file2.c'])
       </file>
       <file name="prog.c">
       int main() { printf("prog.c\n"); }
       </file>
       <file name="file1.c">
       void file1() { printf("file1.c\n"); }
       </file>
       <file name="file2.c">
       void file2() { printf("file2.c\n"); }
       </file>
    </scons_example>

    <para>

    On Linux, a build of this example would look like:

    </para>

    <scons_output example="ex3" os="posix">
       <scons_output_command>scons -Q</scons_output_command>
    </scons_output>

    <para>

    Or on Windows:

    </para>

    <scons_output example="ex3" os="win32">
       <scons_output_command>scons -Q</scons_output_command>
    </scons_output>

  </section>

  <section>
  <title>Making a list of files with &Glob;</title>

    <para>

    You can also use the &Glob; function to find all files matching a
    certain template, using the standard shell pattern matching
    characters <literal>*</literal>, <literal>?</literal>
    and <literal>[abc]</literal> to match any of
    <literal>a</literal>, <literal>b</literal> or <literal>c</literal>.
    <literal>[!abc]</literal> is also supported,
    to match any character <emphasis>except</emphasis>
    <literal>a</literal>, <literal>b</literal> or <literal>c</literal>.
    This makes many multi-source-file builds quite easy:

    </para>

    <sconstruct>
       Program('program', Glob('*.c'))
    </sconstruct>

    <para>

    The SCons man page has more details on using &Glob; with Variant
    directories and Repositories, and returning strings rather than Nodes.

    </para>

  </section>

  <section>
  <title>Specifying Single Files Vs. Lists of Files</title>

    <para>

    We've now shown you two ways to specify
    the source for a program,
    one with a list of files:

    </para>

    <sconstruct>
       Program('hello', ['file1.c', 'file2.c'])
    </sconstruct>

    <para>

    And one with a single file:

    </para>

    <sconstruct>
       Program('hello', 'hello.c')
    </sconstruct>

    <para>

    You could actually put a single file name in a list, too,
    which you might prefer just for the sake of consistency:

    </para>

    <sconstruct>
       Program('hello', ['hello.c'])
    </sconstruct>

    <para>

    &SCons; functions will accept a single file name in either form.
    In fact, internally, &SCons; treats all input as lists of files,
    but allows you to omit the square brackets
    to cut down a little on the typing
    when there's only a single file name.

    </para>

    <important>
    
    <para>

    Although &SCons; functions
    are forgiving about whether or not you
    use a string vs. a list for a single file name,
    Python itself is more strict about
    treating lists and strings differently.
    So where &SCons; allows either
    a string or list:

    </para>

    <sconstruct>
       # The following two calls both work correctly:
       Program('program1', 'program1.c')
       Program('program2', ['program2.c'])
    </sconstruct>

    <para>

    Trying to do "Python things" that mix strings and
    lists will cause errors or lead to incorrect results:

    </para>

    <sconstruct>
       common_sources = ['file1.c', 'file2.c']

       # THE FOLLOWING IS INCORRECT AND GENERATES A PYTHON ERROR
       # BECAUSE IT TRIES TO ADD A STRING TO A LIST:
       Program('program1', common_sources + 'program1.c')

       # The following works correctly, because it's adding two
       # lists together to make another list.
       Program('program2', common_sources + ['program2.c'])
    </sconstruct>

    </important>

  </section>

  <section>
  <title>Making Lists of Files Easier to Read</title>

    <para>

    One drawback to the use of a Python list
    for source files is that 
    each file name must be enclosed in quotes
    (either single quotes or double quotes).
    This can get cumbersome and difficult to read
    when the list of file names is long.
    Fortunately, &SCons; and Python provide a number of ways
    to make sure that
    the &SConstruct; file stays easy to read.

    </para>

    <para>

    To make long lists of file names
    easier to deal with, &SCons; provides a
    &Split; function
    that takes a quoted list of file names,
    with the names separated by spaces or other white-space characters,
    and turns it into a list of separate file names.
    Using the &Split; function turns the
    previous example into:

    </para>

    <programlisting>
       Program('program', Split('main.c file1.c file2.c'))
    </programlisting>

    <para>

    (If you're already familiar with Python,
    you'll have realized that this is similar to the
    <function>split()</function> method
    in the Python standard <function>string</function> module.
    Unlike the <function>string.split()</function> method,
    however, the &Split; function
    does not require a string as input
    and will wrap up a single non-string object in a list,
    or return its argument untouched if it's already a list.
    This comes in handy as a way to make sure
    arbitrary values can be passed to &SCons; functions
    without having to check the type of the variable by hand.)

    </para>

    <para>

    Putting the call to the &Split; function
    inside the &b-Program; call
    can also be a little unwieldy.
    A more readable alternative is to
    assign the output from the &Split; call
    to a variable name,
    and then use the variable when calling the
    &b-Program; function:

    </para>

    <programlisting>
       src_files = Split('main.c file1.c file2.c')
       Program('program', src_files)
    </programlisting>

    <para>

    Lastly, the &Split; function
    doesn't care how much white space separates
    the file names in the quoted string.
    This allows you to create lists of file
    names that span multiple lines,
    which often makes for easier editing:

    </para>

    <programlisting>
       src_files = Split("""main.c
                            file1.c
                            file2.c""")
       Program('program', src_files)
    </programlisting>

    <para>

    (Note in this example that we used
    the Python "triple-quote" syntax,
    which allows a string to contain
    multiple lines.
    The three quotes can be either
    single or double quotes.)

    </para>

  </section>

  <section>
  <title>Keyword Arguments</title>

    <para>

    &SCons; also allows you to identify
    the output file and input source files
    using Python keyword arguments.
    The output file is known as the
    <emphasis>target</emphasis>,
    and the source file(s) are known (logically enough) as the
    <emphasis>source</emphasis>.
    The Python syntax for this is:

    </para>

    <programlisting>
       src_files = Split('main.c file1.c file2.c')
       Program(target = 'program', source = src_files)
    </programlisting>

    <para>

    Because the keywords explicitly identify
    what each argument is,
    you can actually reverse the order if you prefer:

    </para>

    <programlisting>
       src_files = Split('main.c file1.c file2.c')
       Program(source = src_files, target = 'program')
    </programlisting>

    <para>

    Whether or not you choose to use keyword arguments
    to identify the target and source files,
    and the order in which you specify them
    when using keywords,
    are purely personal choices;
    &SCons; functions the same regardless.

    </para>

  </section>

  <section>
  <title>Compiling Multiple Programs</title>

    <para>

    In order to compile multiple programs
    within the same &SConstruct; file,
    simply call the &Program; method
    multiple times,
    once for each program you need to build:

    </para>

    <scons_example name="ex4">
       <file name="SConstruct" printme="1">
       Program('foo.c')
       Program('bar', ['bar1.c', 'bar2.c'])
       </file>
       <file name="foo.c">
       int main() { printf("foo.c\n"); }
       </file>
       <file name="bar1.c">
       int main() { printf("bar1.c\n"); }
       </file>
       <file name="bar2.c">
       void bar2() { printf("bar2.c\n"); }
       </file>
    </scons_example>

    <para>

    &SCons; would then build the programs as follows:

    </para>

    <scons_output example="ex4">
       <scons_output_command>scons -Q</scons_output_command>
    </scons_output>

    <para>

    Notice that &SCons; does not necessarily build the
    programs in the same order in which you specify
    them in the &SConstruct; file.
    &SCons; does, however, recognize that
    the individual object files must be built
    before the resulting program can be built.
    We'll discuss this in greater detail in
    the "Dependencies" section, below.

    </para>

  </section>

  <section>
  <title>Sharing Source Files Between Multiple Programs</title>

    <para>

    It's common to re-use code by sharing source files
    between multiple programs.
    One way to do this is to create a library
    from the common source files,
    which can then be linked into resulting programs.
    (Creating libraries is discussed in
    <xref linkend="chap-libraries"></xref>, below.)

    </para>

    <para>

    A more straightforward, but perhaps less convenient,
    way to share source files between multiple programs
    is simply to include the common files
    in the lists of source files for each program:

    </para>

    <scons_example name="ex5">
       <file name="SConstruct" printme="1">
       Program(Split('foo.c common1.c common2.c'))
       Program('bar', Split('bar1.c bar2.c common1.c common2.c'))
       </file>
       <file name="foo.c">
       int main() { printf("foo.c\n"); }
       </file>
       <file name="bar1.c">
       int main() { printf("bar1.c\n"); }
       </file>
       <file name="bar2.c">
       int bar2() { printf("bar2.c\n"); }
       </file>
       <file name="common1.c">
       void common1() { printf("common1.c\n"); }
       </file>
       <file name="common2.c">
       void common22() { printf("common2.c\n"); }
       </file>
    </scons_example>

    <para>

    &SCons; recognizes that the object files for
    the &common1_c; and &common2_c; source files
    each only need to be built once,
    even though the resulting object files are
    each linked in to both of the resulting executable programs:

    </para>

    <scons_output example="ex5">
       <scons_output_command>scons -Q</scons_output_command>
    </scons_output>

    <para>

    If two or more programs
    share a lot of common source files,
    repeating the common files in the list for each program
    can be a maintenance problem when you need to change the
    list of common files.
    You can simplify this by creating a separate Python list
    to hold the common file names,
    and concatenating it with other lists
    using the Python &plus; operator:

    </para>

    <programlisting>
       common = ['common1.c', 'common2.c']
       foo_files = ['foo.c'] + common
       bar_files = ['bar1.c', 'bar2.c'] + common
       Program('foo', foo_files)
       Program('bar', bar_files)
    </programlisting>

    <para>

    This is functionally equivalent to the previous example.

    </para>

  </section>