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(Part 1) - Add an optional dependency on libboost-iostreams
The main refactoring taking place in this PR is to port the P4-14 and P4-16 lexers and parsers to use the C++ modes of Flex and Bison. In C++ mode, Flex generates a lexer that reads from a `std::istream` object instead of a file descriptor. That produces a bit of an impedance mismatch, because typically before we parse anything we run it through the C preprocessor via `popen()`, and `popen()` uses C `FILE*`-based I/O rather than iostreams. The C++-11 standard library does not include a `FILE*` wrapper that produces an `std::istream`. If we don't want to write and maintain one ourselves (and I'd argue we don't) that leaves us with three options: 1. Stop using `popen()` and implement the subset of C preprocessor features we need directly. 2. Read the entire file in and wrap it in a `std::stringstream` or similar. This obviously isn't as efficient as it could be. 3. Use Boost's IOStreams library to do the job more efficiently. In the large term, my view is that p4lang#1 is the best choice, but in the short run p4lang#3 seems like a win with no real downsides other than adding another dependency. (It's only an additional dependency on Ubuntu, which splits Boost into a number of small packages. On macOS there's actually no change.) In the interest of getting this PR landed ASAP, I've actually implemented both p4lang#2 and p4lang#3, so the Boost IOStreams dependency is optional. I would vastly prefer to make it mandatory, though.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,110 @@ | ||
| dnl @synopsis AX_CXX_CHECK_LIB(libname, functioname, action-if, action-if-not) | ||
| dnl | ||
| dnl The standard AC_CHECK_LIB can not test functions in namespaces. | ||
| dnl Therefore AC_CHECK_LIB(cgicc, cgicc::Cgicc::getVersion) will always | ||
| dnl fail. We need to decompose the functionname into a series of namespaces | ||
| dnl where it gets declared so that it can be used for a link test. | ||
| dnl | ||
| dnl In the first version I did allow namespace::functionname to be a | ||
| dnl reference to a void-argument global functionname (just wrapped in a | ||
| dnl namespace) like its C counterparts would be - but in reality such | ||
| dnl thing does not exist. The only global / static functions are always | ||
| dnl made const-functions which is an attribute mangled along into the | ||
| dnl library function export name. | ||
| dnl | ||
| dnl The normal usage will ask for a test of a class-member function which | ||
| dnl should be presented with a full function spec with arguments given in | ||
| dnl parentheses following the function name - if the function to test for | ||
| dnl does expect arguments then you should add default initial values in the | ||
| dnl prototype (even if they do not exist originally, these are used only | ||
| dnl locally to build a correct function call in the configure test script). | ||
| dnl | ||
| dnl In the current version if you do omit the parenthesis from the macro | ||
| dnl argument then the macro will assume that you want to check for the | ||
| dnl class name - which is really to check for default constructor being | ||
| dnl exported from the given library name. | ||
| dnl | ||
| dnl EXAMPLE: | ||
| dnl AX_CXX_CHECK_LIB(cgicc, [cgicc::HTTPCookie]) | ||
| dnl AX_CXX_CHECK_LIB(cgicc, [cgicc::Cgicc::getVersion () const], | ||
| dnl AX_CXX_CHECK_LIB(boost_regex, [boost::RegEx::Position (int i = 0) const]) | ||
| dnl | ||
| dnl Result: | ||
| dnl Just as the usual AX_CXX_CHECK_LIB - defines HAVE_LIBCGICC | ||
| dnl and adds the libraries to the default library path (and | ||
| dnl uses internally the normal ac_check_lib cache symbol | ||
| dnl like ac_cv_lib_cgicc_cgicc__Cgicc) | ||
| dnl | ||
| dnl Footnote: The C++ language is not good at creating stable library | ||
| dnl interfaces at the binary level - a lot of functionality is usually being | ||
| dnl given as inline functions plus there is hardly a chance to create opaque | ||
| dnl types. Therefore most C++ library tests will only do compile tests using | ||
| dnl the header files. Doing a check_lib is however good to check the link | ||
| dnl dependency before hitting it as an error in the build later. | ||
| dnl | ||
| dnl @category C++ | ||
| dnl @author Guido U. Draheim | ||
| dnl @vesion 2006-12-18 | ||
|
|
||
| AC_DEFUN([AX_CXX_CHECK_LIB], | ||
| [m4_ifval([$3], , [AH_CHECK_LIB([$1])])dnl | ||
| AS_LITERAL_IF([$1], | ||
| [AS_VAR_PUSHDEF([ac_Lib], [ac_cv_lib_$1_$2])], | ||
| [AS_VAR_PUSHDEF([ac_Lib], [ac_cv_lib_$1''_$2])])dnl | ||
| AC_CACHE_CHECK([for $2 in -l$1], ac_Lib, | ||
| [ac_check_lib_save_LIBS=$LIBS | ||
| LIBS="-l$1 $5 $LIBS" | ||
| case "$2" | ||
| in *::*::*\(*) | ||
| AC_LINK_IFELSE([AC_LANG_PROGRAM([ | ||
| namespace `echo "$2" | sed -e "s/::.*//"` | ||
| { class `echo "$2" | sed -e "s/.*::\\(.*\\)::.*/\\1/" -e "s/(.*//"` | ||
| { public: int `echo "$2" | sed -e "s/.*:://" -e "/(/!s/..*/&()/"`; | ||
| }; | ||
| } | ||
| ],[`echo "$2" | sed -e "s/(.*//" -e "s/\\(.*\\)::\\(.*\\)/((\\1*)(0))->\\2/g"`()])], | ||
| [AS_VAR_SET(ac_Lib, yes)], | ||
| [AS_VAR_SET(ac_Lib, no)]) | ||
| ;; *::*::*) | ||
| AC_LINK_IFELSE([AC_LANG_PROGRAM([ | ||
| namespace `echo "$2" | sed -e "s/::.*//"` | ||
| { namespace `echo "$2" | sed -e "s/.*::\\(.*\\)::.*/\\1/"` | ||
| { class `echo "$2" | sed -e "s/.*:://"` | ||
| { public: `echo "$2" | sed -e "s/.*:://"` (); | ||
| }; | ||
| } | ||
| } | ||
| ],[new $2()])], | ||
| [AS_VAR_SET(ac_Lib, yes)], | ||
| [AS_VAR_SET(ac_Lib, no)]) | ||
| ;; *::*\(*) | ||
| AC_LINK_IFELSE([AC_LANG_PROGRAM([ | ||
| class `echo "$2" | sed -e "s/\\(.*\\)::.*/\\1/" -e "s/(.*//"` | ||
| { public: int `echo "$2" | sed -e "s/.*:://" -e "/(/!s/..*/&()/"`; | ||
| }; | ||
| ],[`echo "$2" | sed -e "s/(.*//" -e "s/\\(.*\\)::\\(.*\\)/((\\1*)(0))->\\2/g"`()])], | ||
| [AS_VAR_SET(ac_Lib, yes)], | ||
| [AS_VAR_SET(ac_Lib, no)]) | ||
| ;; *::*) | ||
| AC_LINK_IFELSE([AC_LANG_PROGRAM([ | ||
| namespace `echo "$2" | sed -e "s/::.*//"` | ||
| { class `echo "$2" | sed -e "s/.*:://"` | ||
| { public: `echo "$2" | sed -e "s/.*:://"` (); | ||
| }; | ||
| } | ||
| ],[new $2()])], | ||
| [AS_VAR_SET(ac_Lib, yes)], | ||
| [AS_VAR_SET(ac_Lib, no)]) | ||
| ;; *) | ||
| AC_LINK_IFELSE([AC_LANG_CALL([], [$2])], | ||
| [AS_VAR_SET(ac_Lib, yes)], | ||
| [AS_VAR_SET(ac_Lib, no)]) | ||
| ;; esac | ||
| LIBS=$ac_check_lib_save_LIBS]) | ||
| AS_IF([test AS_VAR_GET(ac_Lib) = yes], | ||
| [m4_default([$3], [AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_LIB$1)) | ||
| LIBS="-l$1 $LIBS" | ||
| ])], | ||
| [$4])dnl | ||
| AS_VAR_POPDEF([ac_Lib])dnl | ||
| ])# AC_CHECK_LIB |