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1#! /usr/bin/env python
2
3# Selectively preprocess #ifdef / #ifndef statements.
4# Usage:
5# ifdef [-Dname] ... [-Uname] ... [file] ...
6#
7# This scans the file(s), looking for #ifdef and #ifndef preprocessor
8# commands that test for one of the names mentioned in the -D and -U
9# options.  On standard output it writes a copy of the input file(s)
10# minus those code sections that are suppressed by the selected
11# combination of defined/undefined symbols.  The #if(n)def/#else/#else
12# lines themselfs (if the #if(n)def tests for one of the mentioned
13# names) are removed as well.
14
15# Features: Arbitrary nesting of recognized and unrecognized
16# preprocesor statements works correctly.  Unrecognized #if* commands
17# are left in place, so it will never remove too much, only too
18# little.  It does accept whitespace around the '#' character.
19
20# Restrictions: There should be no comments or other symbols on the
21# #if(n)def lines.  The effect of #define/#undef commands in the input
22# file or in included files is not taken into account.  Tests using
23# #if and the defined() pseudo function are not recognized.  The #elif
24# command is not recognized.  Improperly nesting is not detected.
25# Lines that look like preprocessor commands but which are actually
26# part of comments or string literals will be mistaken for
27# preprocessor commands.
28
29import sys
30import getopt
31
32defs = []
33undefs = []
34
35def main():
36    opts, args = getopt.getopt(sys.argv[1:], 'D:U:')
37    for o, a in opts:
38        if o == '-D':
39            defs.append(a)
40        if o == '-U':
41            undefs.append(a)
42    if not args:
43        args = ['-']
44    for filename in args:
45        if filename == '-':
46            process(sys.stdin, sys.stdout)
47        else:
48            f = open(filename, 'r')
49            process(f, sys.stdout)
50            f.close()
51
52def process(fpi, fpo):
53    keywords = ('if', 'ifdef', 'ifndef', 'else', 'endif')
54    ok = 1
55    stack = []
56    while 1:
57        line = fpi.readline()
58        if not line: break
59        while line[-2:] == '\\\n':
60            nextline = fpi.readline()
61            if not nextline: break
62            line = line + nextline
63        tmp = line.strip()
64        if tmp[:1] != '#':
65            if ok: fpo.write(line)
66            continue
67        tmp = tmp[1:].strip()
68        words = tmp.split()
69        keyword = words[0]
70        if keyword not in keywords:
71            if ok: fpo.write(line)
72            continue
73        if keyword in ('ifdef', 'ifndef') and len(words) == 2:
74            if keyword == 'ifdef':
75                ko = 1
76            else:
77                ko = 0
78            word = words[1]
79            if word in defs:
80                stack.append((ok, ko, word))
81                if not ko: ok = 0
82            elif word in undefs:
83                stack.append((ok, not ko, word))
84                if ko: ok = 0
85            else:
86                stack.append((ok, -1, word))
87                if ok: fpo.write(line)
88        elif keyword == 'if':
89            stack.append((ok, -1, ''))
90            if ok: fpo.write(line)
91        elif keyword == 'else' and stack:
92            s_ok, s_ko, s_word = stack[-1]
93            if s_ko < 0:
94                if ok: fpo.write(line)
95            else:
96                s_ko = not s_ko
97                ok = s_ok
98                if not s_ko: ok = 0
99                stack[-1] = s_ok, s_ko, s_word
100        elif keyword == 'endif' and stack:
101            s_ok, s_ko, s_word = stack[-1]
102            if s_ko < 0:
103                if ok: fpo.write(line)
104            del stack[-1]
105            ok = s_ok
106        else:
107            sys.stderr.write('Unknown keyword %s\n' % keyword)
108    if stack:
109        sys.stderr.write('stack: %s\n' % stack)
110
111if __name__ == '__main__':
112    main()
113