Re: How to check for linker argument support?

[Bent Bisballe Nyeng]

On 12/10/16 12:22, Bent Bisballe Nyeng wrote:
> Hi list
>
> I want to use the --no-undefined linker argument through the
> -Wl,--no-undefined CXXFLAGS. This is only supported by gcc but has a
> clang alternative: -Wl,-undefined,error.
> I have tried writing a test in my configure.ac script to figure out
> which one should be used, but my test reports 'yes' on both gcc and
> clang, so clang never falls back to it's own variant.
> My test looks like this:
>
> dnl ===========================
> dnl Check for -Wl,--no-undefined or -Wl,-undefined,error support
> dnl ===========================
> AC_LANG_PUSH([C++])
> TMP_CXXFLAGS="$CXXFLAGS"
> AC_MSG_CHECKING([whether CXX supports '-Wl,--no-undefined'])
> CXXFLAGS="-Wall -Werror -Wl,--no-undefined"
> AC_LINK_IFELSE([AC_LANG_PROGRAM([])],
>     [ AC_MSG_RESULT([yes])
>         NO_UNDEFINED_PARAM=-Wl,--no-undefined
>     ],
>     [ AC_MSG_RESULT([no])
>         AC_MSG_CHECKING([whether CXX supports '-Wl,-undefined,error'])
>         CXXFLAGS="-Wall -Werror -Wl,-undefined,error"
>         AC_LINK_IFELSE([AC_LANG_PROGRAM([])],
>             [AC_MSG_RESULT([yes])
>                 NO_UNDEFINED_PARAM=-Wl,-undefined,error
>             ],
>             [AC_MSG_RESULT([no])
>                 NO_UNDEFINED_PARAM=""
>             ]
>         )
>     ]
> )
> CXXFLAGS="$TMP_CXXFLAGS"
> AC_LANG_POP([C++])
>
> Any input to what I might be doing wrong?

I found out that I needed to use AC_COMPILE_IFELSE instead of 
AC_LINK_IFELSE because test need to be done through the compiler in 
order to use the -Wall and -Werror and thereby result in the error the 
way I the test needs it to.

Kind regards
Bent Bisballe Nyeng