FindBISON

Finds the Bison command-line parser generator and provides a CMake command to generate custom build rules for using Bison:

find_package(BISON [<version>] [...])

Bison is a parser generator that replaced earlier Yacc (Yet Another Compiler-Compiler). On Unix-like systems, most common implementation is GNU Bison. On Windows, this module looks for Windows-compatible Bison, if installed.

Result Variables

This module defines the following variables:

BISON_FOUND: Boolean indicating whether (the requested version of) Bison was found.
BISON_VERSION: The version of Bison found.

Cache Variables

The following cache variables may also be set:

BISON_EXECUTABLE: The path to the bison command-line program.

Commands

This module provides the following command if bison is found:

bison_target

Creates a custom build rule to generate a parser file from a Yacc file using Bison:

bison_target(
  <name>
  <input-yacc-file>
  <output-parser-file>
  [DEFINES_FILE <header>]
  [VERBOSE [<file>]]       # The [<file>] argument is deprecated
  [REPORT_FILE <file>]
  [OPTIONS <options>...]
  [COMPILE_FLAGS <string>] # Deprecated
)

Changed in version 3.14: When policy CMP0088 is set to NEW, bison runs in the CMAKE_CURRENT_BINARY_DIR directory.

<name>

String used as an identifier for this command invocation.

<input-yacc-file>

The path to an input Yacc source file (.y). If given as a relative path, it will be interpreted relative to the current source directory (CMAKE_CURRENT_SOURCE_DIR).

<output-parser-file>

The path of the output parser file to be generated by Bison. If given as a relative path, it will be interpreted relative to the current Bison working directory.

DEFINES_FILE <header>

Added in version 3.4.

By default, Bison can generate a header file containing the list of tokens. This option allows specifying a custom <header> file to be generated by Bison. If given as a relative path, it will be interpreted relative to the current Bison working directory.

VERBOSE [<file>]

Enables generation of a verbose grammar and parser report. By default, the report file is created in the current Bison working directory and named <output-parser-filename>.output.

<file>: Deprecated since version 3.7: Use VERBOSE REPORT_FILE <file>.

Specifies the path to which the report file should be copied. This argument is retained for backward compatibility and only works when the <output-parser-file> is specified as an absolute path.

REPORT_FILE <file>

Added in version 3.7.

Used in combination with VERBOSE to specify a custom path for the report output <file>, overriding the default location. If given as a relative path, it will be interpreted relative to the current Bison working directory.

OPTIONS <options>...

Added in version 4.0.

A semicolon-separated list of extra options added to the bison command line.

COMPILE_FLAGS <string>

Deprecated since version 4.0: Superseded by OPTIONS <options>....

A string of space-separated extra options added to the bison command line. A semicolon-separated list will not work.

Command variables

This command also defines the following variables:

BISON_<name>_DEFINED: Boolean indicating whether this command was successfully invoked.
BISON_<name>_INPUT: The input source file, an alias for <input-yacc-file>.
BISON_<name>_OUTPUT_SOURCE: The output parser file generated by bison.
BISON_<name>_OUTPUT_HEADER: The header file generated by bison, if any.
BISON_<name>_OUTPUTS: A list of files generated by bison, including the output parser file, header file, and report file.
BISON_<name>_OPTIONS: Added in version 4.0.

A list of command-line options used for the bison command.
BISON_<name>_COMPILE_FLAGS: Deprecated since version 4.0: Superseded by BISON_<name>_OPTIONS variable with the same value.

A list of command-line options used for the bison command.

Examples

Examples: Finding Bison

Finding Bison:

find_package(BISON)

Finding Bison with a minimum required version:

find_package(BISON 2.1.3)

Finding Bison and making it required (if Bison is not found, processing stops with an error message):

find_package(BISON 2.1.3 REQUIRED)

Example: Generating Parser

Finding Bison and adding input Yacc source file parser.y to be processed by Bison into parser.cpp source file with header parser.h at build phase:

find_package(BISON)

if(BISON_FOUND)
  bison_target(MyParser parser.y parser.cpp DEFINES_FILE parser.h)
endif()

add_executable(Foo main.cpp ${BISON_MyParser_OUTPUTS})

Examples: Command-line Options

Adding additional command-line options to the bison executable can be passed as a list. For example, adding the -Wall option to report all warnings, and --no-lines (-l) to not generate #line directives:

find_package(BISON)

if(BISON_FOUND)
  bison_target(MyParser parser.y parser.cpp OPTIONS -Wall --no-lines)
endif()

Generator expressions can be used in the OPTIONS <options>... argument. For example, to add the --debug (-t) option only for the Debug build type:

find_package(BISON)

if(BISON_FOUND)
  bison_target(MyParser parser.y parser.cpp OPTIONS $<$<CONFIG:Debug>:-t>)
endif()