ifdef.py

#! /usr/bin/env python

# Selectively preprocess #ifdef / #ifndef statements.
# Usage:
# ifdef [-Dname] ... [-Uname] ... [file] ...
#
# This scans the file(s), looking for #ifdef and #ifndef preprocessor
# commands that test for one of the names mentioned in the -D and -U
# options. On standard output it writes a copy of the input file(s)
# minus those code sections that are suppressed by the selected
# combination of defined/undefined symbols. The #if(n)def/#else/#else
# lines themselves (if the #if(n)def tests for one of the mentioned
# names) are removed as well.

# Features: Arbitrary nesting of recognized and unrecognized
# preprocessor statements works correctly. Unrecognized #if* commands
# are left in place, so it will never remove too much, only too
# little. It does accept whitespace around the '#' character.

# Restrictions: There should be no comments or other symbols on the
# #if(n)def lines. The effect of #define/#undef commands in the input
# file or in included files is not taken into account. Tests using
# #if and the defined() pseudo function are not recognized. The #elif
# command is not recognized. Improperly nesting is not detected.
# Lines that look like preprocessor commands but which are actually
# part of comments or string literals will be mistaken for
# preprocessor commands.

importsys
importgetopt

defs= []
undefs= []

defmain():
opts, args=getopt.getopt(sys.argv[1:], 'D:U:')
foro, ainopts:
ifo=='-D':
defs.append(a)
ifo=='-U':
undefs.append(a)
ifnotargs:
args= ['-']
forfilenameinargs:
iffilename=='-':
process(sys.stdin, sys.stdout)
else:
f=open(filename, 'r')
process(f, sys.stdout)
f.close()

defprocess(fpi, fpo):
keywords= ('if', 'ifdef', 'ifndef', 'else', 'endif')
ok=1
stack= []
while1:
line=fpi.readline()
ifnotline: break
whileline[-2:] =='\\\n':
nextline=fpi.readline()
ifnotnextline: break
line=line+nextline
tmp=line.strip()
iftmp[:1] !='#':
ifok: fpo.write(line)
continue
tmp=tmp[1:].strip()
words=tmp.split()
keyword=words[0]
ifkeywordnotinkeywords:
ifok: fpo.write(line)
continue
ifkeywordin ('ifdef', 'ifndef') andlen(words) ==2:
ifkeyword=='ifdef':
ko=1
else:
ko=0
word=words[1]
ifwordindefs:
stack.append((ok, ko, word))
ifnotko: ok=0
elifwordinundefs:
stack.append((ok, notko, word))
ifko: ok=0
else:
stack.append((ok, -1, word))
ifok: fpo.write(line)
elifkeyword=='if':
stack.append((ok, -1, ''))
ifok: fpo.write(line)
elifkeyword=='else'andstack:
s_ok, s_ko, s_word=stack[-1]
ifs_ko<0:
ifok: fpo.write(line)
else:
s_ko=nots_ko
ok=s_ok
ifnots_ko: ok=0
stack[-1] =s_ok, s_ko, s_word
elifkeyword=='endif'andstack:
s_ok, s_ko, s_word=stack[-1]
ifs_ko<0:
ifok: fpo.write(line)
delstack[-1]
ok=s_ok
else:
sys.stderr.write('Unknown keyword %s\n'%keyword)
ifstack:
sys.stderr.write('stack: %s\n'%stack)

if__name__=='__main__':
main()