1UNIFDEF(1) BSD General Commands Manual UNIFDEF(1)
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4 unifdef, unifdefall — remove preprocessor conditionals from code
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7 unifdef [-BbcdeKknst] [-Ipath] [-Dsym[=val]] [-Usym] [-iDsym[=val]]
8 [-iUsym] ... [-o outfile] [infile]
9 unifdefall [-Ipath] ... file
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12 The unifdef utility selectively processes conditional cpp(1) directives.
13 It removes from a file both the directives and any additional text that
14 they specify should be removed, while otherwise leaving the file alone.
15 The unifdef utility acts on #if, #ifdef, #ifndef, #elif, #else, and
17 #endif lines. A directive is only processed if the symbols specified on
18 the command line are sufficient to allow unifdef to get a definite value
19 for its control expression. If the result is false, the directive and
20 the following lines under its control are removed. If the result is
21 true, only the directive is removed. An #ifdef or #ifndef directive is
22 passed through unchanged if its controlling symbol is not specified on
23 the command line. Any #if or #elif control expression that has an
24 unknown value or that unifdef cannot parse is passed through unchanged.
25 By default, unifdef ignores #if and #elif lines with constant expres‐
26 sions; it can be told to process them by specifying the -k flag on the
27 command line.
28 It understands a commonly-used subset of the expression syntax for #if
30 and #elif lines: integer constants, integer values of symbols defined on
31 the command line, the defined() operator, the operators !, <, >, <=, >=,
32 ==, !=, &&, ||, and parenthesized expressions. A kind of “short circuit”
33 evaluation is used for the && operator: if either operand is definitely
34 false then the result is false, even if the value of the other operand is
35 unknown. Similarly, if either operand of || is definitely true then the
36 result is true.
37 In most cases, the unifdef utility does not distinguish between object-
39 like macros (without arguments) and function-like arguments (with argu‐
40 ments). If a macro is not explicitly defined, or is defined with the -D
41 flag on the command-line, its arguments are ignored. If a macro is
42 explicitly undefined on the command line with the -U flag, it may not
43 have any arguments since this leads to a syntax error.
44 The unifdef utility understands just enough about C to know when one of
46 the directives is inactive because it is inside a comment, or affected by
47 a backslash-continued line. It spots unusually-formatted preprocessor
48 directives and knows when the layout is too odd for it to handle.
49 A script called unifdefall can be used to remove all conditional cpp(1)
51 directives from a file. It uses unifdef -s and cpp -dM to get lists of
52 all the controlling symbols and their definitions (or lack thereof), then
53 invokes unifdef with appropriate arguments to process the file.
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56 -Dsym[=val]
57 Specify that a symbol is defined, and optionally specify what
58 value to give it for the purpose of handling #if and #elif direc‐
59 tives.
60 -Usym Specify that a symbol is undefined. If the same symbol appears
62 in more than one argument, the last occurrence dominates.
63 -B Compress blank lines around a deleted section. Mutually exclu‐
65 sive with the -b option.
66 -b Replace removed lines with blank lines instead of deleting them.
68 Mutually exclusive with the -B option.
69 -c If the -c flag is specified, then the operation of unifdef is
71 complemented, i.e., the lines that would have been removed or
72 blanked are retained and vice versa.
73 -d Turn on printing of degugging messages.
75 -e Because unifdef processes its input one line at a time, it cannot
77 remove preprocessor directives that span more than one line. The
78 most common example of this is a directive with a multi-line com‐
79 ment hanging off its right hand end. By default, if unifdef has
80 to process such a directive, it will complain that the line is
81 too obfuscated. The -e option changes the behaviour so that,
82 where possible, such lines are left unprocessed instead of
83 reporting an error.
84 -K Always treat the result of && and || operators as unknown if
86 either operand is unknown, instead of short-circuiting when
87 unknown operands can't affect the result. This option is for
88 compatibility with older versions of unifdef.
89 -k Process #if and #elif lines with constant expressions. By
91 default, sections controlled by such lines are passed through
92 unchanged because they typically start “#if 0” and are used as a
93 kind of comment to sketch out future or past development. It
94 would be rude to strip them out, just as it would be for normal
95 comments.
96 -n Add #line directives to the output following any deleted lines,
98 so that errors produced when compiling the output file correspond
99 to line numbers in the input file.
100 -o outfile
102 Write output to the file outfile instead of the standard output.
103 If outfile is the same as the input file, the output is written
104 to a temporary file which is renamed into place when unifdef com‐
105 pletes successfully.
106 -s Instead of processing the input file as usual, this option causes
108 unifdef to produce a list of symbols that appear in expressions
109 that unifdef understands. It is useful in conjunction with the
110 -dM option of cpp(1) for creating unifdef command lines.
111 -t Disables parsing for C comments and line continuations, which is
113 useful for plain text.
114 -iDsym[=val]
116 -iUsym Ignore #ifdefs. If your C code uses #ifdefs to delimit non-C
117 lines, such as comments or code which is under construction, then
118 you must tell unifdef which symbols are used for that purpose so
119 that it will not try to parse comments and line continuations
120 inside those #ifdefs. You can specify ignored symbols with
121 -iDsym[=val] and -iUsym similar to -Dsym[=val] and -Usym above.
122 -Ipath Specifies to unifdefall an additional place to look for #include
124 files. This option is ignored by unifdef for compatibility with
125 cpp(1) and to simplify the implementation of unifdefall.
126 The unifdef utility copies its output to stdout and will take its input
128 from stdin if no file argument is given.
129 The unifdef utility works nicely with the -Dsym option of diff(1).
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133 The unifdef utility exits 0 if the output is an exact copy of the input,
134 1 if not, and 2 if in trouble.
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137 Too many levels of nesting.
138 Inappropriate #elif, #else or #endif.
140 Obfuscated preprocessor control line.
142 Premature EOF (with the line number of the most recent unterminated #if).
144 EOF in comment.
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148 cpp(1), diff(1)
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151 The unifdef command appeared in 2.9BSD. ANSI C support was added in
152 FreeBSD 4.7.
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155 The original implementation was written by Dave Yost <Dave@Yost.com>.
156 Tony Finch <dot@dotat.at> rewrote it to support ANSI C.
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159 Expression evaluation is very limited.
160 Preprocessor control lines split across more than one physical line
162 (because of comments or backslash-newline) cannot be handled in every
163 situation.
164 Trigraphs are not recognized.
166 There is no support for symbols with different definitions at different
168 points in the source file.
169 The text-mode and ignore functionality does not correspond to modern
171 cpp(1) behaviour.
172BSD January 19, 2010 BSD