.\" Man page generated from reStructuredText.
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.TH "CMAKE-LANGUAGE" "7" "Aug 20, 2020" "3.18.2" "CMake"
.SH NAME
cmake-language \- CMake Language Reference
.
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.SH ORGANIZATION
.sp
CMake input files are written in the “CMake Language” in source files
named \fBCMakeLists.txt\fP or ending in a \fB\&.cmake\fP file name extension.
.sp
CMake Language source files in a project are organized into:
.INDENT 0.0
.IP \(bu 2
\fI\%Directories\fP (\fBCMakeLists.txt\fP),
.IP \(bu 2
\fI\%Scripts\fP (\fB<script>.cmake\fP), and
.IP \(bu 2
\fI\%Modules\fP (\fB<module>.cmake\fP).
.UNINDENT
.SS Directories
.sp
When CMake processes a project source tree, the entry point is
a source file called \fBCMakeLists.txt\fP in the top\-level source
directory.  This file may contain the entire build specification
or use the \fBadd_subdirectory()\fP command to add subdirectories
to the build.  Each subdirectory added by the command must also
contain a \fBCMakeLists.txt\fP file as the entry point to that
directory.  For each source directory whose \fBCMakeLists.txt\fP file
is processed CMake generates a corresponding directory in the build
tree to act as the default working and output directory.
.SS Scripts
.sp
An individual \fB<script>.cmake\fP source file may be processed
in \fIscript mode\fP by using the \fBcmake(1)\fP command\-line tool
with the \fB\-P\fP option.  Script mode simply runs the commands in
the given CMake Language source file and does not generate a
build system.  It does not allow CMake commands that define build
targets or actions.
.SS Modules
.sp
CMake Language code in either \fI\%Directories\fP or \fI\%Scripts\fP may
use the \fBinclude()\fP command to load a \fB<module>.cmake\fP
source file in the scope of the including context.
See the \fBcmake\-modules(7)\fP manual page for documentation
of modules included with the CMake distribution.
Project source trees may also provide their own modules and
specify their location(s) in the \fBCMAKE_MODULE_PATH\fP
variable.
.SH SYNTAX
.SS Encoding
.sp
A CMake Language source file may be written in 7\-bit ASCII text for
maximum portability across all supported platforms.  Newlines may be
encoded as either \fB\en\fP or \fB\er\en\fP but will be converted to \fB\en\fP
as input files are read.
.sp
Note that the implementation is 8\-bit clean so source files may
be encoded as UTF\-8 on platforms with system APIs supporting this
encoding.  In addition, CMake 3.2 and above support source files
encoded in UTF\-8 on Windows (using UTF\-16 to call system APIs).
Furthermore, CMake 3.0 and above allow a leading UTF\-8
\fI\%Byte\-Order Mark\fP in source files.
.SS Source Files
.sp
A CMake Language source file consists of zero or more
\fI\%Command Invocations\fP separated by newlines and optionally
spaces and \fI\%Comments\fP:
.sp
.nf
\fBfile        \fP ::=  \fI\%file_element\fP*
\fBfile_element\fP ::=  \fI\%command_invocation\fP \fI\%line_ending\fP |
                  (\fI\%bracket_comment\fP|\fI\%space\fP)* \fI\%line_ending\fP
\fBline_ending \fP ::=  \fI\%line_comment\fP? \fI\%newline\fP
\fBspace       \fP ::=  <match \(aq[ \et]+\(aq>
\fBnewline     \fP ::=  <match \(aq\en\(aq>

.fi
.sp
Note that any source file line not inside \fI\%Command Arguments\fP or
a \fI\%Bracket Comment\fP can end in a \fI\%Line Comment\fP\&.
.SS Command Invocations
.sp
A \fIcommand invocation\fP is a name followed by paren\-enclosed arguments
separated by whitespace:
.sp
.nf
\fBcommand_invocation \fP ::=  \fI\%space\fP* \fI\%identifier\fP \fI\%space\fP* \(aq(\(aq \fI\%arguments\fP \(aq)\(aq
\fBidentifier         \fP ::=  <match \(aq[A\-Za\-z_][A\-Za\-z0\-9_]*\(aq>
\fBarguments          \fP ::=  \fI\%argument\fP? \fI\%separated_arguments\fP*
\fBseparated_arguments\fP ::=  \fI\%separation\fP+ \fI\%argument\fP? |
                         \fI\%separation\fP* \(aq(\(aq \fI\%arguments\fP \(aq)\(aq
\fBseparation         \fP ::=  \fI\%space\fP | \fI\%line_ending\fP

.fi
.sp
For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
add_executable(hello world.c)
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
Command names are case\-insensitive.
Nested unquoted parentheses in the arguments must balance.
Each \fB(\fP or \fB)\fP is given to the command invocation as
a literal \fI\%Unquoted Argument\fP\&.  This may be used in calls
to the \fBif()\fP command to enclose conditions.
For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
if(FALSE AND (FALSE OR TRUE)) # evaluates to FALSE
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
CMake versions prior to 3.0 require command name identifiers
to be at least 2 characters.
.sp
CMake versions prior to 2.8.12 silently accept an \fI\%Unquoted Argument\fP
or a \fI\%Quoted Argument\fP immediately following a \fI\%Quoted Argument\fP and
not separated by any whitespace.  For compatibility, CMake 2.8.12 and
higher accept such code but produce a warning.
.UNINDENT
.UNINDENT
.SS Command Arguments
.sp
There are three types of arguments within \fI\%Command Invocations\fP:
.sp
.nf
\fBargument\fP ::=  \fI\%bracket_argument\fP | \fI\%quoted_argument\fP | \fI\%unquoted_argument\fP

.fi
.SS Bracket Argument
.sp
A \fIbracket argument\fP, inspired by \fI\%Lua\fP long bracket syntax,
encloses content between opening and closing “brackets” of the
same length:
.sp
.nf
\fBbracket_argument\fP ::=  \fI\%bracket_open\fP \fI\%bracket_content\fP \fI\%bracket_close\fP
\fBbracket_open    \fP ::=  \(aq[\(aq \(aq=\(aq* \(aq[\(aq
\fBbracket_content \fP ::=  <any text not containing a \fI\%bracket_close\fP with
                       the same number of \(aq=\(aq as the \fI\%bracket_open\fP>
\fBbracket_close   \fP ::=  \(aq]\(aq \(aq=\(aq* \(aq]\(aq

.fi
.sp
An opening bracket is written \fB[\fP followed by zero or more \fB=\fP followed
by \fB[\fP\&.  The corresponding closing bracket is written \fB]\fP followed
by the same number of \fB=\fP followed by \fB]\fP\&.
Brackets do not nest.  A unique length may always be chosen
for the opening and closing brackets to contain closing brackets
of other lengths.
.sp
Bracket argument content consists of all text between the opening
and closing brackets, except that one newline immediately following
the opening bracket, if any, is ignored.  No evaluation of the
enclosed content, such as \fI\%Escape Sequences\fP or \fI\%Variable References\fP,
is performed.  A bracket argument is always given to the command
invocation as exactly one argument.
.sp
For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
message([=[
This is the first line in a bracket argument with bracket length 1.
No \e\-escape sequences or ${variable} references are evaluated.
This is always one argument even though it contains a ; character.
The text does not end on a closing bracket of length 0 like ]].
It does end in a closing bracket of length 1.
]=])
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
CMake versions prior to 3.0 do not support bracket arguments.
They interpret the opening bracket as the start of an
\fI\%Unquoted Argument\fP\&.
.UNINDENT
.UNINDENT
.SS Quoted Argument
.sp
A \fIquoted argument\fP encloses content between opening and closing
double\-quote characters:
.sp
.nf
\fBquoted_argument    \fP ::=  \(aq"\(aq \fI\%quoted_element\fP* \(aq"\(aq
\fBquoted_element     \fP ::=  <any character except \(aq\e\(aq or \(aq"\(aq> |
                         \fI\%escape_sequence\fP |
                         \fI\%quoted_continuation\fP
\fBquoted_continuation\fP ::=  \(aq\e\(aq \fI\%newline\fP

.fi
.sp
Quoted argument content consists of all text between opening and
closing quotes.  Both \fI\%Escape Sequences\fP and \fI\%Variable References\fP
are evaluated.  A quoted argument is always given to the command
invocation as exactly one argument.
.sp
For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
message("This is a quoted argument containing multiple lines.
This is always one argument even though it contains a ; character.
Both \e\e\-escape sequences and ${variable} references are evaluated.
The text does not end on an escaped double\-quote like \e".
It does end in an unescaped double quote.
")
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
The final \fB\e\fP on any line ending in an odd number of backslashes
is treated as a line continuation and ignored along with the
immediately following newline character.  For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
message("\e
This is the first line of a quoted argument. \e
In fact it is the only line but since it is long \e
the source code uses line continuation.\e
")
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
CMake versions prior to 3.0 do not support continuation with \fB\e\fP\&.
They report errors in quoted arguments containing lines ending in
an odd number of \fB\e\fP characters.
.UNINDENT
.UNINDENT
.SS Unquoted Argument
.sp
An \fIunquoted argument\fP is not enclosed by any quoting syntax.
It may not contain any whitespace, \fB(\fP, \fB)\fP, \fB#\fP, \fB"\fP, or \fB\e\fP
except when escaped by a backslash:
.sp
.nf
\fBunquoted_argument\fP ::=  \fI\%unquoted_element\fP+ | \fI\%unquoted_legacy\fP
\fBunquoted_element \fP ::=  <any character except whitespace or one of \(aq()#"\e\(aq> |
                       \fI\%escape_sequence\fP
\fBunquoted_legacy  \fP ::=  <see note in text>

.fi
.sp
Unquoted argument content consists of all text in a contiguous block
of allowed or escaped characters.  Both \fI\%Escape Sequences\fP and
\fI\%Variable References\fP are evaluated.  The resulting value is divided
in the same way \fI\%Lists\fP divide into elements.  Each non\-empty element
is given to the command invocation as an argument.  Therefore an
unquoted argument may be given to a command invocation as zero or
more arguments.
.sp
For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
foreach(arg
    NoSpace
    Escaped\e Space
    This;Divides;Into;Five;Arguments
    Escaped\e;Semicolon
    )
  message("${arg}")
endforeach()
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
To support legacy CMake code, unquoted arguments may also contain
double\-quoted strings (\fB"..."\fP, possibly enclosing horizontal
whitespace), and make\-style variable references (\fB$(MAKEVAR)\fP).
.sp
Unescaped double\-quotes must balance, may not appear at the
beginning of an unquoted argument, and are treated as part of the
content.  For example, the unquoted arguments \fB\-Da="b c"\fP,
\fB\-Da=$(v)\fP, and \fBa" "b"c"d\fP are each interpreted literally.
They may instead be written as quoted arguments \fB"\-Da=\e"b c\e""\fP,
\fB"\-Da=$(v)"\fP, and \fB"a\e" \e"b\e"c\e"d"\fP, respectively.
.sp
Make\-style references are treated literally as part of the content
and do not undergo variable expansion.  They are treated as part
of a single argument (rather than as separate \fB$\fP, \fB(\fP,
\fBMAKEVAR\fP, and \fB)\fP arguments).
.sp
The above “unquoted_legacy” production represents such arguments.
We do not recommend using legacy unquoted arguments in new code.
Instead use a \fI\%Quoted Argument\fP or a \fI\%Bracket Argument\fP to
represent the content.
.UNINDENT
.UNINDENT
.SS Escape Sequences
.sp
An \fIescape sequence\fP is a \fB\e\fP followed by one character:
.sp
.nf
\fBescape_sequence \fP ::=  \fI\%escape_identity\fP | \fI\%escape_encoded\fP | \fI\%escape_semicolon\fP
\fBescape_identity \fP ::=  \(aq\e\(aq <match \(aq[^A\-Za\-z0\-9;]\(aq>
\fBescape_encoded  \fP ::=  \(aq\et\(aq | \(aq\er\(aq | \(aq\en\(aq
\fBescape_semicolon\fP ::=  \(aq\e;\(aq

.fi
.sp
A \fB\e\fP followed by a non\-alphanumeric character simply encodes the literal
character without interpreting it as syntax.  A \fB\et\fP, \fB\er\fP, or \fB\en\fP
encodes a tab, carriage return, or newline character, respectively. A \fB\e;\fP
outside of any \fI\%Variable References\fP  encodes itself but may be used in an
\fI\%Unquoted Argument\fP to encode the \fB;\fP without dividing the argument
value on it.  A \fB\e;\fP inside \fI\%Variable References\fP encodes the literal
\fB;\fP character.  (See also policy \fBCMP0053\fP documentation for
historical considerations.)
.SS Variable References
.sp
A \fIvariable reference\fP has the form \fB${<variable>}\fP and is
evaluated inside a \fI\%Quoted Argument\fP or an \fI\%Unquoted Argument\fP\&.
A variable reference is replaced by the value of the variable,
or by the empty string if the variable is not set.
Variable references can nest and are evaluated from the
inside out, e.g. \fB${outer_${inner_variable}_variable}\fP\&.
.sp
Literal variable references may consist of alphanumeric characters,
the characters \fB/_.+\-\fP, and \fI\%Escape Sequences\fP\&.  Nested references
may be used to evaluate variables of any name.  See also policy
\fBCMP0053\fP documentation for historical considerations and reasons why
the \fB$\fP is also technically permitted but is discouraged.
.sp
The \fI\%Variables\fP section documents the scope of variable names
and how their values are set.
.sp
An \fIenvironment variable reference\fP has the form \fB$ENV{<variable>}\fP\&.
See the \fI\%Environment Variables\fP section for more information.
.sp
A \fIcache variable reference\fP has the form \fB$CACHE{<variable>}\fP\&.
See \fBCACHE\fP for more information.
.sp
The \fBif()\fP command has a special condition syntax that
allows for variable references in the short form \fB<variable>\fP
instead of \fB${<variable>}\fP\&.
However, environment and cache variables always need to be
referenced as \fB$ENV{<variable>}\fP or \fB$CACHE{<variable>}\fP\&.
.SS Comments
.sp
A comment starts with a \fB#\fP character that is not inside a
\fI\%Bracket Argument\fP, \fI\%Quoted Argument\fP, or escaped with \fB\e\fP
as part of an \fI\%Unquoted Argument\fP\&.  There are two types of
comments: a \fI\%Bracket Comment\fP and a \fI\%Line Comment\fP\&.
.SS Bracket Comment
.sp
A \fB#\fP immediately followed by a \fI\%bracket_open\fP forms a
\fIbracket comment\fP consisting of the entire bracket enclosure:
.sp
.nf
\fBbracket_comment\fP ::=  \(aq#\(aq \fI\%bracket_argument\fP

.fi
.sp
For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#[[This is a bracket comment.
It runs until the close bracket.]]
message("First Argument\en" #[[Bracket Comment]] "Second Argument")
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
CMake versions prior to 3.0 do not support bracket comments.
They interpret the opening \fB#\fP as the start of a \fI\%Line Comment\fP\&.
.UNINDENT
.UNINDENT
.SS Line Comment
.sp
A \fB#\fP not immediately followed by a \fI\%bracket_open\fP forms a
\fIline comment\fP that runs until the end of the line:
.sp
.nf
\fBline_comment\fP ::=  \(aq#\(aq <any text not starting in a \fI\%bracket_open\fP
                       and not containing a \fI\%newline\fP>

.fi
.sp
For example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
# This is a line comment.
message("First Argument\en" # This is a line comment :)
        "Second Argument") # This is a line comment.
.ft P
.fi
.UNINDENT
.UNINDENT
.SH CONTROL STRUCTURES
.SS Conditional Blocks
.sp
The \fBif()\fP/\fBelseif()\fP/\fBelse()\fP/\fBendif()\fP
commands delimit code blocks to be executed conditionally.
.SS Loops
.sp
The \fBforeach()\fP/\fBendforeach()\fP and
\fBwhile()\fP/\fBendwhile()\fP commands delimit code
blocks to be executed in a loop.  Inside such blocks the
\fBbreak()\fP command may be used to terminate the loop
early whereas the \fBcontinue()\fP command may be used
to start with the next iteration immediately.
.SS Command Definitions
.sp
The \fBmacro()\fP/\fBendmacro()\fP, and
\fBfunction()\fP/\fBendfunction()\fP commands delimit
code blocks to be recorded for later invocation as commands.
.SH VARIABLES
.sp
Variables are the basic unit of storage in the CMake Language.
Their values are always of string type, though some commands may
interpret the strings as values of other types.
The \fBset()\fP and \fBunset()\fP commands explicitly
set or unset a variable, but other commands have semantics
that modify variables as well.
Variable names are case\-sensitive and may consist of almost
any text, but we recommend sticking to names consisting only
of alphanumeric characters plus \fB_\fP and \fB\-\fP\&.
.sp
Variables have dynamic scope.  Each variable “set” or “unset”
creates a binding in the current scope:
.INDENT 0.0
.TP
.B Function Scope
\fI\%Command Definitions\fP created by the \fBfunction()\fP command
create commands that, when invoked, process the recorded commands
in a new variable binding scope.  A variable “set” or “unset”
binds in this scope and is visible for the current function and
any nested calls within it, but not after the function returns.
.TP
.B Directory Scope
Each of the \fI\%Directories\fP in a source tree has its own variable
bindings.  Before processing the \fBCMakeLists.txt\fP file for a
directory, CMake copies all variable bindings currently defined
in the parent directory, if any, to initialize the new directory
scope.  CMake \fI\%Scripts\fP, when processed with \fBcmake \-P\fP, bind
variables in one “directory” scope.
.sp
A variable “set” or “unset” not inside a function call binds
to the current directory scope.
.TP
.B Persistent Cache
CMake stores a separate set of “cache” variables, or “cache entries”,
whose values persist across multiple runs within a project build
tree.  Cache entries have an isolated binding scope modified only
by explicit request, such as by the \fBCACHE\fP option of the
\fBset()\fP and \fBunset()\fP commands.
.UNINDENT
.sp
When evaluating \fI\%Variable References\fP, CMake first searches the
function call stack, if any, for a binding and then falls back
to the binding in the current directory scope, if any.  If a
“set” binding is found, its value is used.  If an “unset” binding
is found, or no binding is found, CMake then searches for a
cache entry.  If a cache entry is found, its value is used.
Otherwise, the variable reference evaluates to an empty string.
The \fB$CACHE{VAR}\fP syntax can be used to do direct cache entry
lookups.
.sp
The \fBcmake\-variables(7)\fP manual documents the many variables
that are provided by CMake or have meaning to CMake when set
by project code.
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
CMake reserves identifiers that:
.INDENT 0.0
.IP \(bu 2
begin with \fBCMAKE_\fP (upper\-, lower\-, or mixed\-case), or
.IP \(bu 2
begin with \fB_CMAKE_\fP (upper\-, lower\-, or mixed\-case), or
.IP \(bu 2
begin with \fB_\fP followed by the name of any \fBCMake Command\fP\&.
.UNINDENT
.UNINDENT
.UNINDENT
.SH ENVIRONMENT VARIABLES
.sp
Environment Variables are like ordinary \fI\%Variables\fP, with the
following differences:
.INDENT 0.0
.TP
.B Scope
Environment variables have global scope in a CMake process.
They are never cached.
.TP
.B References
\fI\%Variable References\fP have the form \fB$ENV{<variable>}\fP\&.
.TP
.B Initialization
Initial values of the CMake environment variables are those of
the calling process.
Values can be changed using the \fBset()\fP and \fBunset()\fP
commands.
These commands only affect the running CMake process,
not the system environment at large.
Changed values are not written back to the calling process,
and they are not seen by subsequent build or test processes.
.UNINDENT
.sp
The \fBcmake\-env\-variables(7)\fP manual documents environment
variables that have special meaning to CMake.
.SH LISTS
.sp
Although all values in CMake are stored as strings, a string
may be treated as a list in certain contexts, such as during
evaluation of an \fI\%Unquoted Argument\fP\&.  In such contexts, a string
is divided into list elements by splitting on \fB;\fP characters not
following an unequal number of \fB[\fP and \fB]\fP characters and not
immediately preceded by a \fB\e\fP\&.  The sequence \fB\e;\fP does not
divide a value but is replaced by \fB;\fP in the resulting element.
.sp
A list of elements is represented as a string by concatenating
the elements separated by \fB;\fP\&.  For example, the \fBset()\fP
command stores multiple values into the destination variable
as a list:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
set(srcs a.c b.c c.c) # sets "srcs" to "a.c;b.c;c.c"
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
Lists are meant for simple use cases such as a list of source
files and should not be used for complex data processing tasks.
Most commands that construct lists do not escape \fB;\fP characters
in list elements, thus flattening nested lists:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
set(x a "b;c") # sets "x" to "a;b;c", not "a;b\e;c"
.ft P
.fi
.UNINDENT
.UNINDENT
.SH COPYRIGHT
2000-2020 Kitware, Inc. and Contributors
.\" Generated by docutils manpage writer.
.