[RFA,2/2] Add -Wduplicated-cond

  This adds -Wduplicated-cond to warnings.m4.  This caught one bug.

I tried adding -Wduplicated-branches as well, but it results in some
spurious failures from code like this in cgen.h:

    #define CGEN_ATTR_TYPE(n) \
    struct { unsigned int bool_; \
	     CGEN_ATTR_VALUE_TYPE nonbool[(n) ? (n) : 1]; }

This will trigger a warning if passed n==1, which seems like a
perfectly valid thing to do; and there were other issues like this as
well.

2018-04-21  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.
	* warning.m4 (AM_GDB_WARNINGS): Add -Wduplicated-cond.

gdbserver/ChangeLog
2018-04-21  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.
---
 gdb/ChangeLog           |  5 +++++
 gdb/configure           | 27 ++++++++++++++-------------
 gdb/gdbserver/ChangeLog |  4 ++++
 gdb/gdbserver/configure | 32 ++++++++++++++++++++------------
 gdb/warning.m4          |  3 ++-
 5 files changed, 45 insertions(+), 26 deletions(-)
  

On 04/21/2018 10:47 PM, Tom Tromey wrote:

> diff --git a/gdb/configure b/gdb/configure
> index b313152018..29efb4b81c 100755
> --- a/gdb/configure
> +++ b/gdb/configure
> @@ -4463,9 +4463,9 @@ else
>  fi
>  
>    if test "$plugins" = "yes"; then
> -    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing dlopen" >&5
> -$as_echo_n "checking for library containing dlopen... " >&6; }
> -if test "${ac_cv_search_dlopen+set}" = set; then :
> +    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing dlsym" >&5
> +$as_echo_n "checking for library containing dlsym... " >&6; }
> +if test "${ac_cv_search_dlsym+set}" = set; then :
>    $as_echo_n "(cached) " >&6
>  else
>    ac_func_search_save_LIBS=$LIBS
> @@ -4478,11 +4478,11 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
>  #ifdef __cplusplus
>  extern "C"
>  #endif
> -char dlopen ();
> +char dlsym ();
>  int
>  main ()
>  {
> -return dlopen ();
> +return dlsym ();
>    ;
>    return 0;
>  }
> @@ -4495,25 +4495,25 @@ for ac_lib in '' dl; do
>      LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
>    fi
>    if ac_fn_c_try_link "$LINENO"; then :
> -  ac_cv_search_dlopen=$ac_res
> +  ac_cv_search_dlsym=$ac_res
>  fi
>  rm -f core conftest.err conftest.$ac_objext \
>      conftest$ac_exeext
> -  if test "${ac_cv_search_dlopen+set}" = set; then :
> +  if test "${ac_cv_search_dlsym+set}" = set; then :
>    break
>  fi
>  done
> -if test "${ac_cv_search_dlopen+set}" = set; then :
> +if test "${ac_cv_search_dlsym+set}" = set; then :
>  
>  else
> -  ac_cv_search_dlopen=no
> +  ac_cv_search_dlsym=no
>  fi
>  rm conftest.$ac_ext
>  LIBS=$ac_func_search_save_LIBS
>  fi
> -{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_dlopen" >&5
> -$as_echo "$ac_cv_search_dlopen" >&6; }
> -ac_res=$ac_cv_search_dlopen
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_dlsym" >&5
> +$as_echo "$ac_cv_search_dlsym" >&6; }
> +ac_res=$ac_cv_search_dlsym
>  if test "$ac_res" != no; then :
>    test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
>  
> @@ -15365,7 +15365,8 @@ build_warnings="-Wall -Wpointer-arith \
>  -Wempty-body -Wunused-but-set-parameter -Wunused-but-set-variable \
>  -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
>  -Wno-mismatched-tags \
> --Wno-error=deprecated-register"
> +-Wno-error=deprecated-register \
> +-Wduplicated-cond"
>  
>  case "${host}" in
>    *-*-mingw32*)
> diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
> index ab09261946..48af8310d9 100755
> --- a/gdb/gdbserver/configure
> +++ b/gdb/gdbserver/configure
> @@ -4658,7 +4658,7 @@ program_transform_name=`$as_echo "$program_transform_name" | sed "$ac_script"`
>  # We require a C++11 compiler.  Check if one is available, and if
>  # necessary, set CXX_DIALECT to some -std=xxx switch.
>  
> -      ax_cxx_compile_cxx11_required=true
> +  ax_cxx_compile_alternatives="11 0x"    ax_cxx_compile_cxx11_required=true
>    ac_ext=cpp
>  ac_cpp='$CXXCPP $CPPFLAGS'
>  ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -4974,7 +4974,8 @@ $as_echo "$ax_cv_cxx_compile_cxx11" >&6; }
>    fi
>  
>      if test x$ac_success = xno; then
> -    for switch in -std=gnu++11 -std=gnu++0x; do
> +    for alternative in ${ax_cxx_compile_alternatives}; do
> +      switch="-std=gnu++${alternative}"
>        cachevar=`$as_echo "ax_cv_cxx_compile_cxx11_$switch" | $as_tr_sh`
>        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports C++11 features with $switch" >&5
>  $as_echo_n "checking whether $CXX supports C++11 features with $switch... " >&6; }
> @@ -5292,16 +5293,17 @@ $as_echo "$ac_res" >&6; }
>    fi
>  
>      if test x$ac_success = xno; then
> -                for switch in -std=c++11 -std=c++0x +std=c++11 "-h std=c++11"; do
> -      cachevar=`$as_echo "ax_cv_cxx_compile_cxx11_$switch" | $as_tr_sh`
> -      { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports C++11 features with $switch" >&5
> +                for alternative in ${ax_cxx_compile_alternatives}; do
> +      for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
> +        cachevar=`$as_echo "ax_cv_cxx_compile_cxx11_$switch" | $as_tr_sh`
> +        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports C++11 features with $switch" >&5
>  $as_echo_n "checking whether $CXX supports C++11 features with $switch... " >&6; }
>  if { as_var=$cachevar; eval "test \"\${$as_var+set}\" = set"; }; then :
>    $as_echo_n "(cached) " >&6
>  else
>    ac_save_CXX="$CXX"
> -         CXX="$CXX $switch"
> -         cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +           CXX="$CXX $switch"
> +           cat confdefs.h - <<_ACEOF >conftest.$ac_ext
>  /* end confdefs.h.  */
>  
>  
> @@ -5596,14 +5598,18 @@ else
>    eval $cachevar=no
>  fi
>  rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> -         CXX="$ac_save_CXX"
> +           CXX="$ac_save_CXX"
>  fi
>  eval ac_res=\$$cachevar
>  	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
>  $as_echo "$ac_res" >&6; }
> -      if eval test x\$$cachevar = xyes; then
> -        CXX_DIALECT="$switch"
> -        ac_success=yes
> +        if eval test x\$$cachevar = xyes; then
> +          CXX_DIALECT="$switch"
> +          ac_success=yes
> +          break
> +        fi
> +      done
> +      if test x$ac_success = xyes; then
>          break
>        fi
>      done
The patch looks fine to me, but the above looks like unrelated changes.
Very much looks like gdbserver/configure was not regenerated
when gdb/warning.m4 was last touched for -Wno-error=deprecated-register,
and  gdb's configure hadn't picked up the changes to config/plugin.m4
yet either.

Could you please push the obvious preliminary patch that just
regenerates gdb/configure and gdbserver/configure,
then rebase your patch on top of that.

I've not looked at the ARM patch; Alan, do you know who can
lend a hand with that?

Thanks,
Pedro Alves
  

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> Could you please push the obvious preliminary patch that just
Pedro> regenerates gdb/configure and gdbserver/configure,
Pedro> then rebase your patch on top of that.

I did this the other day.

Tom