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c++makefilecmakebisonflex-lexer

CMake and Flex/Bison

I am converting my build system from configure/make to a cmake system

The system has some autogenerated files, from bison/flex. The original makefile commands are:

bison --defines=tokens.h --output=parser.cpp parser.y
flex --outfile=scanner.cpp scanner.l

I came across this ancient link which seems to explain how to do it, but when i run cmake with the following custom commands, nothing appears to happen (no error messages, no file generation)

FIND_PACKAGE(BISON REQUIRED)
IF(BISON_FOUND)
    ADD_CUSTOM_COMMAND(
      SOURCE ${CMAKE_SOURCE_DIR}/src/rcdgen/parser.y
      COMMAND ${BISON_EXECUTABLE}
      ARGS --defines=${CMAKE_SOURCE_DIR}/src/rcdgen/tokens.h
           -o ${CMAKE_SOURCE_DIR}/src/rcdgen/parser.cpp
           ${CMAKE_SOURCE_DIR}/src/rcdgen/parser.y
      COMMENT "Generating parser.cpp"
      OUTPUT ${CMAKE_SOURCE_DIR}/src/rcdgen/parser.cpp
    )
ENDIF(BISON_FOUND)

FIND_PACKAGE(FLEX REQUIRED)
IF(FLEX_FOUND)
    ADD_CUSTOM_COMMAND(
      SOURCE ${CMAKE_SOURCE_DIR}/src/rcdgen/scanner.l
      COMMAND ${FLEX_EXECUTABLE}
      ARGS -o${CMAKE_SOURCE_DIR}/src/rcdgen/parser.cpp
           ${CMAKE_SOURCE_DIR}/src/rcdgen/scanner.l
      COMMENT "Generating scanner.cpp"
      OUTPUT ${CMAKE_SOURCE_DIR}/src/rcdgen/scanner.cpp
    )
ENDIF(FLEX_FOUND)

I am new to cmake, so it's a bit confusing to me. Does anyone have any idea what a working custom_command would be?

Solution

  • The new hotness for bison usage is actually documented in FindBison So for a simple parser project:

    find_package(BISON)
BISON_TARGET(MyParser parser.y ${CMAKE_CURRENT_BINARY_DIR}/parser.cpp
             DEFINES_FILE ${CMAKE_CURRENT_BINARY_DIR}/parser.h)
add_executable(Foo main.cpp ${BISON_MyParser_OUTPUTS})

    is what you'd do. Likewise for Flex.