Re: [PATCH] [gdb/build] Check if libsource-highlight is usable

[Lancelot SIX via Gdb-patches <gdb-patches@sourceware.org>]

> diff --git a/gdb/configure.ac b/gdb/configure.ac
> index d4cfb6a7624..e4fed3c575c 100644
> --- a/gdb/configure.ac
> +++ b/gdb/configure.ac
> @@ -1248,11 +1248,48 @@ either use --disable-source-highlight or dnl
>            ;;
>        esac
>  
> -      SRCHIGH_CFLAGS=`${pkg_config_prog_path} --cflags source-highlight`
> -      SRCHIGH_LIBS=`${pkg_config_prog_path} --libs source-highlight`
> -      AC_DEFINE([HAVE_SOURCE_HIGHLIGHT], 1,
> -                [Define to 1 if the source-highlight library is available])
> -      AC_MSG_RESULT([yes])
> +      srchigh_pkg_cflags=`${pkg_config_prog_path} --cflags source-highlight`
> +      srchigh_pkg_libs=`${pkg_config_prog_path} --libs source-highlight`
> +
> +      # Now that we have found a source-highlight library, check if we can use
> +      # it.  In particular, we're trying to detect the situation that the
> +      # library is using the new libstdc++ library abi ( see
> +      # https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html )
> +      # while the compiler being used to compile gdb is using the old abi.
> +      # Such a situation will result in an undefined reference to
> +      # srchilite::SourceHighlight::SourceHighlight(std::string const&).
> +      # This situation can occur when f.i. using a source highlight library
> +      # compiled with g++ 7.5.0 while building gdb with g++ 4.8.5.
> +      AC_LANG_PUSH(C++)
> +      save_CFLAGS=$CFLAGS
> +      save_LDFLAGS=$LDFLAGS
> +      CFLAGS="$CFLAGS $srchigh_pkg_cflags"
> +      LDFLAGS="$LDFLAGS $srchigh_pkg_libs"
> +      AC_LINK_IFELSE(
> +        [AC_LANG_PROGRAM(
> +          [#include <srchilite/sourcehighlight.h>],
> +          [std::string outlang = "esc.outlang";
> +           new srchilite::SourceHighlight (outlang);]
> +        )],
> +        [have_usable_source_highlight=yes],
> +        [have_usable_source_highlight=no]
> +      )
> +      CFLAGS="$SAVE_CFLAGS"
> +      LDFLAGS="$SAVE_LDFLAGS"
> +      AC_LANG_POP(C++)
> +
> +      if test "${have_usable_source_highlight}" = "yes"; then
> +        AC_DEFINE([HAVE_SOURCE_HIGHLIGHT], 1,
> +                  [Define to 1 if the source-highlight library is available])
> +        AC_MSG_RESULT([yes])
> +        SRCHIGH_CFLAGS="$srchigh_pkg_cflags"
> +        SRCHIGH_LIBS="$srchigh_pkg_libs"
> +      else
> +	AC_MSG_RESULT([no])
> +	if test "${enable_source_highlight}" = "yes"; then

Hi,

I do not know what it the indentation policy for the configure.ac file,
but you use tabs in the 'AC_MSG_RESULT' and 'if test' lines above (2
lines above), and nowhere else.

The rest of the file does not seem to be completely consistent regarding
this particular subject, so I do not know if there is a preferred
formatting that should be used, but I guess that having the same across
the patch could make sense.

Otherwise, and for what it is worth, this looks reasonable to me.

Best,
Lancelot.

> +          AC_MSG_ERROR([source-highlight in your system could not be used])
> +        fi
> +      fi 
>      else
>        AC_MSG_RESULT([no])
>        if test "${enable_source_highlight}" = "yes"; then
> 
> base-commit: fd0ff19bf435b267caae6a1ae04e7b4a4ba64f5b
> -- 
> 2.26.2
>