1UNIFDEF(1) Programmer's Manual UNIFDEF(1)
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4 unifdef, unifdefall — remove preprocessor conditionals from code
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7 unifdef [-bBcdehKkmnsStV] [-Ipath] [-[i]Dsym[=val]] [-[i]Usym] ...
8 [-f defile] [-x {012}] [-M backext] [-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, using macros specified in -D and -U command line options or
18 in -f definitions files. A directive is processed if the macro specifi‐
19 cations are sufficient to provide a definite value for its control
20 expression. If the result is false, the directive and the following
21 lines under its control are removed. If the result is true, only the
22 directive is removed. An #ifdef or #ifndef directive is passed through
23 unchanged if its controlling macro is not specified. Any #if or #elif
24 control expression that has an unknown value or that unifdef cannot parse
25 is passed through unchanged. By default, unifdef ignores #if and #elif
26 lines with constant expressions; it can be told to process them by speci‐
27 fying the -k flag on the command line.
28 It understands a commonly-used subset of the expression syntax for #if
30 and #elif lines: integer constants, integer values of macros 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 When evaluating an expression, unifdef does not expand macros first. The
39 value of a macro must be a simple number, not an expression. A limited
40 form of indirection is allowed, where one macro's value is the name of
41 another.
42 In most cases, unifdef does not distinguish between object-like macros
44 (without arguments) and function-like macros (with arguments). A func‐
45 tion-like macro invocation can appear in #if and #elif control expres‐
46 sions. If the macro is not explicitly defined, or is defined with the -D
47 flag on the command-line, or with #define in a -f definitions file, its
48 arguments are ignored. If a macro is explicitly undefined on the command
49 line with the -U flag, or with #undef in a -f definitions file, it may
50 not have any arguments since this leads to a syntax error.
51 The unifdef utility understands just enough about C to know when one of
53 the directives is inactive because it is inside a comment, or affected by
54 a backslash-continued line. It spots unusually-formatted preprocessor
55 directives and knows when the layout is too odd for it to handle.
56 A script called unifdefall can be used to remove all conditional cpp(1)
58 directives from a file. It uses unifdef -s and cpp -dM to get lists of
59 all the controlling macros and their definitions (or lack thereof), then
60 invokes unifdef with appropriate arguments to process the file.
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63 -Dsym=val
64 Specify that a macro is defined to a given value.
65 -Dsym Specify that a macro is defined to the value 1.
67 -Usym Specify that a macro is undefined.
69 If the same macro appears in more than one argument, the last
71 occurrence dominates.
72 -iDsym[=val]
74 -iUsym C strings, comments, and line continuations are ignored within
75 #ifdef and #ifndef blocks controlled by macros specified with
76 these options.
77 -f defile
79 The file defile contains #define and #undef preprocessor direc‐
80 tives, which have the same effect as the corresponding -D and -U
81 command-line arguments. You can have multiple -f arguments and
82 mix them with -D and -U arguments; later options override earlier
83 ones.
84 Each directive must be on a single line. Object-like macro defi‐
86 nitions (without arguments) are set to the given value. Func‐
87 tion-like macro definitions (with arguments) are treated as if
88 they are set to 1.
89 -b Replace removed lines with blank lines instead of deleting them.
91 Mutually exclusive with the -B option.
92 -B Compress blank lines around a deleted section. Mutually exclu‐
94 sive with the -b option.
95 -c Complement, i.e., lines that would have been removed or blanked
97 are retained and vice versa.
98 -d Turn on printing of debugging messages.
100 -e By default, unifdef will report an error if it needs to remove a
102 preprocessor directive that spans more than one line, for exam‐
103 ple, if it has a multi-line comment hanging off its right hand
104 end. The -e flag makes it ignore the line instead.
105 -h Print help.
107 -Ipath Specifies to unifdefall an additional place to look for #include
109 files. This option is ignored by unifdef for compatibility with
110 cpp(1) and to simplify the implementation of unifdefall.
111 -K Always treat the result of && and || operators as unknown if
113 either operand is unknown, instead of short-circuiting when
114 unknown operands can't affect the result. This option is for
115 compatibility with older versions of unifdef.
116 -k Process #if and #elif lines with constant expressions. By
118 default, sections controlled by such lines are passed through
119 unchanged because they typically start “#if 0” and are used as a
120 kind of comment to sketch out future or past development. It
121 would be rude to strip them out, just as it would be for normal
122 comments.
123 -m Modify one or more input files in place.
125 -M backext
127 Modify input files in place, and keep backups of the original
128 files by appending the backext to the input filenames.
129 -n Add #line directives to the output following any deleted lines,
131 so that errors produced when compiling the output file correspond
132 to line numbers in the input file.
133 -o outfile
135 Write output to the file outfile instead of the standard output
136 when processing a single file.
137 -s Instead of processing an input file as usual, this option causes
139 unifdef to produce a list of macros that are used in preprocessor
140 directive controlling expressions.
141 -S Like the -s option, but the nesting depth of each macro is also
143 printed. This is useful for working out the number of possible
144 combinations of interdependent defined/undefined macros.
145 -t Disables parsing for C strings, comments, and line continuations,
147 which is useful for plain text. This is a blanket version of the
148 -iD and -iU flags.
149 -V Print version details.
151 -x {012}
153 Set exit status mode to zero, one, or two. See the EXIT STATUS
154 section below for details.
155 The unifdef utility takes its input from stdin if there are no file argu‐
157 ments. You must use the -m or -M options if there are multiple input
158 files. You can specify inut from stdin or output to stdout with ‘-’.
159 The unifdef utility works nicely with the -Dsym option of diff(1).
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163 In normal usage the unifdef utility's exit status depends on the mode set
164 using the -x option.
165 If the exit mode is zero (the default) then unifdef exits with status 0
167 if the output is an exact copy of the input, or with status 1 if the out‐
168 put differs.
169 If the exit mode is one, unifdef exits with status 1 if the output is
171 unmodified or 0 if it differs.
172 If the exit mode is two, unifdef exits with status zero in both cases.
174 In all exit modes, unifdef exits with status 2 if there is an error.
176 The exit status is 0 if the -h or -V command line options are given.
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180 Too many levels of nesting.
181 Inappropriate #elif, #else or #endif.
183 Obfuscated preprocessor control line.
185 Premature EOF (with the line number of the most recent unterminated #if).
187 EOF in comment.
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191 cpp(1), diff(1)
192 The unifdef home page is http://dotat.at/prog/unifdef
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196 The unifdef command appeared in 2.9BSD. ANSI C support was added in
197 FreeBSD 4.7.
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200 The original implementation was written by Dave Yost <Dave@Yost.com>.
201 Tony Finch <dot@dotat.at> rewrote it to support ANSI C.
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204 Expression evaluation is very limited.
205 Handling one line at a time means preprocessor directives split across
207 more than one physical line (because of comments or backslash-newline)
208 cannot be handled in every situation.
209 Trigraphs are not recognized.
211 There is no support for macros with different definitions at different
213 points in the source file.
214 The text-mode and ignore functionality does not correspond to modern
216 cpp(1) behaviour.
217 January 7, 2014