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dnl @synopsis AX_ISC_RPATH
dnl
dnl @summary figure out whether and which "rpath" linker option is available
dnl
dnl This macro checks if the linker supports an option to embed a path
dnl to a runtime library (often installed in an uncommon place), such as the
dnl commonly used -R option. If found, it sets the ISC_RPATH_FLAG variable to
dnl the found option flag. The main configure.ac can use it as follows:
dnl if test "x$ISC_RPATH_FLAG" != "x"; then
dnl LDFLAGS="$LDFLAGS ${ISC_RPATH_FLAG}/usr/local/lib/some_library"
dnl fi
dnl
dnl If you pass --disable-rpath to configure, ISC_RPATH_FLAG is not set
AC_DEFUN([AX_ISC_RPATH], [
AC_ARG_ENABLE(rpath,
[AS_HELP_STRING([--disable-rpath],[don't hardcode library path into binaries])],
rpath=$enableval, rpath=yes)
if test x$rpath != xno; then
# We'll tweak both CXXFLAGS and CCFLAGS so this function will work
# whichever language is used in the main script. Note also that it's not
#LDFLAGS; technically this is a linker flag, but we've noticed $LDFLAGS
# can be placed where the compiler could interpret it as a compiler
# option, leading to subtle failure mode. So, in the check below using
# the compiler flag is safer (in the actual Makefiles the flag should be
# set in LDFLAGS).
CXXFLAGS_SAVED="$CXXFLAGS"
CXXFLAGS="$CXXFLAGS -Wl,-R/usr/lib"
CCFLAGS_SAVED="$CCFLAGS"
CCFLAGS="$CCFLAGS -Wl,-R/usr/lib"
# check -Wl,-R and -R rather than gcc specific -rpath to be as portable
# as possible. -Wl,-R seems to be safer, so we try it first. In some
# cases -R is not actually recognized but AC_LINK_IFELSE doesn't fail due
# to that.
AC_MSG_CHECKING([whether -Wl,-R flag is available in linker])
AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], [[]])],
[AC_MSG_RESULT(yes)
ISC_RPATH_FLAG=-Wl,-R
],
[AC_MSG_RESULT(no)
AC_MSG_CHECKING([whether -R flag is available in linker])
# Apple clang 5.1 is now considers unknown parameters
# passed to linker (ld) as errors. However, the same
# unknown parameters passed to compiler (g++) are merely
# treated as warnings. To make sure that we pick those
# up, is to use -Werror.
CXXFLAGS="$CXXFLAGS_SAVED -R/usr/lib"
CCFLAGS="$CCFLAGS_SAVED -R/usr/lib"
AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], [[]])],
[AC_MSG_RESULT([yes; note that -R is more sensitive about the position in option arguments])
ISC_RPATH_FLAG=-R],
[AC_MSG_RESULT(no)])
]
)
CXXFLAGS=$CXXFLAGS_SAVED
CCFLAGS=$CCFLAGS_SAVED
fi
])dnl AX_ISC_RPATH
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