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Re: [PATCH 1/2] Use POSIX nm to simplify AIX export_symbols_cmds.


From: David Edelsohn
Subject: Re: [PATCH 1/2] Use POSIX nm to simplify AIX export_symbols_cmds.
Date: Mon, 21 Mar 2016 13:14:54 -0400

On Mon, Mar 21, 2016 at 12:50 PM, Michael Haubenwallner
<address@hidden> wrote:
>
> On 03/21/2016 03:47 PM, David Edelsohn wrote:
>> On Mon, Mar 21, 2016 at 4:49 AM, Michael Haubenwallner
>> <address@hidden> wrote:
>>>
>>> On 03/20/2016 01:04 AM, David Edelsohn wrote:
>>>> I agree with this in principle, but I'm not convinced that the patch
>>>> itself is correct.
>>>
>>> Thanks!
>>>
>>>> I also would have split the MS-compatible part of the patch as a
>>>> separate step.  It is not listed in the ChangeLog and just confuses
>>>> the patch.
>>>
>>> This is just a reordering of existing code - these lines are removed
>>> below, and the ChangeLog part is "Reorder to allow for platform specific
>>> hooks during transformation of global_symbol_pipe into C source code."
>>>
>>>> I don't see that this emits TLS symbols.  Global TLS symbols are not
>>>> in the symcode list.
>>>
>>> Isn't the "L" for TLS symbols?
>>>
>>> +    symcode='[[BDLTVWZ]]'
>>
>> Sorry, I was confused by the two cases for "aix" and the case for
>> "GNU" within AIX.
>>
>>>
>>> But indeed I've failed to identify the symcode of "weak TLS" symbols,
>>> except for "L*" with AIX nm in unspecified mode (nm -l, no -B or -P)
>>> Neither AIX nm nor GNU nm docs explicitly tell about weak TLS symbols.
>>> Is it possible for TLS symbols to be weak at all?
>
> For GNU nm I've identified the "C" (common) symcode to be "weak" as well.
>
> But still I'm unsure about TLS symbols: Always import them as "strong"?
>

We're limited to strong TLS symbols.

>>>> Global symbol pipe and exclude symbols somehow restricts the symbols
>>>> to the non "dot" symbols?
>>>
>>> Yes - but this is what the existing code does as well:
>>> '... && ([substr](\$ 1,1,1) != ".") ..'
>>
>> Is that in your patch or existing code?  Your patch removes the
>> current substr($3,1,1).
>
> In current code there is substr($3,1,1) for GNU nm (BSD mode) and
> substr($1,1,1) for AIX nm (POSIX mode), both identifying the "dot"
> symbols as to be *removed* from the list of exported symbols.
>
> This patch leaves removal of the "dot" symbols up to $global_symbol_pipe,
> which does remove them due to not being a valid C symbol name.
>
>>>> The export_symbols_cmds awk command does not have matching quotes, so
>>>> I don't know what is going on.
>>>>
>>>> awk '\''{ kw = "" } /^[[VWZ]] / { kw = " weak" } { print $ 3 kw }'\''
>>>>
>>>> you're starting and ending with '\" which seems odd. why aren't these
>>>> complementary?
>>>
>>> The awk argument is passed between ['], as it contains ["].
>>> Escaping [\] the ['] is done outside any other string. Read as:
>>> _LT_TAGVAR(...)=['$NM ... | awk '][\']['{ ... }'][\'][' | sort ...']
>>> Indeed I can add [] here if you like.
>>
>> Ah, well, this is turning into a very complex statement.  GCC requires
>> GNU Awk and most developers use Bash, but does this work correctly
>> with AIX awk and AIX Ksh?
>
> This awk program is quite simple and works with AIX awk too. The AWK
> variable is not promoted into the final libtool script, and I don't
> want to have projects using libtool to require GNU Awk in general.
>
> Most shells do not take [\] within two ['] as escapement,
> so I do the escaping of ['] outside any string. Usually,
>  $ echo '\''
> will leave you with a string open to be continued, while
>  $ echo \'
> gives a single ['].
>
> And this one doesn't feel more readable either:
> _LT_TAGVAR(...)='$NM ... | awk '"'"'{ ... }'"'"' | sort ...'
>
> What about this one:
> _LT_TAGVAR(...)='$NM ... | awk '[\']'{ ... }'[\']' | sort ...'
>

I think we're lost all pretense of elegance, so whatever works.

Thanks, David

> Thanks!
> /haubi/
>
>>>
>>>>
>>>> Thanks, David
>>>>
>>>> On Wed, Mar 2, 2016 at 11:19 AM, Michael Haubenwallner
>>>> <address@hidden> wrote:
>>>>> * m4/libtool.m4 (LT_PATH_NM): Detect POSIX-compatible nm for AIX.  In
>>>>> BSD mode, the AIX nm does not tell whether a symbol is weak, need to use
>>>>> POSIX mode instead.
>>>>> (_LT_CMD_GLOBAL_SYMBOLS): Support POSIX-compatible nm.  Reorder to allow
>>>>> for platform specific hooks during transformation of global_symbol_pipe
>>>>> into C source code.  For AIX, set hook to transform even weak text
>>>>> symbols as text symbols.
>>>>> (_LT_LINKER_SHLIBS): Use global_symbol_pipe to simplify forming the
>>>>> export_symbols_cmds for AIX.
>>>>> ---
>>>>>  m4/libtool.m4 | 101 
>>>>> ++++++++++++++++++++++++++++++++--------------------------
>>>>>  1 file changed, 55 insertions(+), 46 deletions(-)
>>>>>
>>>>> diff --git a/m4/libtool.m4 b/m4/libtool.m4
>>>>> index 2c0e657..6134522 100644
>>>>> --- a/m4/libtool.m4
>>>>> +++ b/m4/libtool.m4
>>>>> @@ -3755,10 +3755,10 @@ _LT_DECL([], [want_nocaseglob], [1],
>>>>>
>>>>>  # LT_PATH_NM
>>>>>  # ----------
>>>>> -# find the pathname to a BSD- or MS-compatible name lister
>>>>> +# find the pathname to a BSD-, POSIX- or MS-compatible name lister
>>>>>  AC_DEFUN([LT_PATH_NM],
>>>>>  [AC_REQUIRE([AC_PROG_CC])dnl
>>>>> -AC_CACHE_CHECK([for BSD- or MS-compatible name lister (nm)], 
>>>>> lt_cv_path_NM,
>>>>> +AC_CACHE_CHECK([for BSD-, POSIX- or MS-compatible name lister (nm)], 
>>>>> lt_cv_path_NM,
>>>>>  [if test -n "$NM"; the
>>>>>    # Let the user override the test.
>>>>>    lt_cv_path_NM=$NM
>>>>> @@ -3808,6 +3808,26 @@ else
>>>>>    : ${lt_cv_path_NM=no}
>>>>>  fi])
>>>>>  if test no != "$lt_cv_path_NM"; then
>>>>> +  case $host_os in
>>>>> +  aix[[4-9]]*)
>>>>> +    # With AIX nm we need the '-l' flag to get the "weak" information
>>>>> +    # for the Import File, but '-l' is ignored with the '-B' flag.  So
>>>>> +    # we use the '-P' (POSIX) flag instead.  As users often provide the
>>>>> +    # '-B' flag, which conflicts with '-P', we drop any provided flag.
>>>>> +    # AIX nm needs the '-C' flag to disable demangling.  For both GNU
>>>>> +    # and AIX nm, the '-g' flag shows public (global) symbols only,
>>>>> +    # and the '-p' flag disables sorting to improve performance.
>>>>> +    set dummy $lt_cv_path_NM
>>>>> +    case address@hidden|@2 -V 2>&1` in
>>>>> +    *GNU* | *'with BFD'*)
>>>>> +      lt_cv_path_NM="@S|@2 -Bgp"
>>>>> +      ;;
>>>>> +    *)
>>>>> +      lt_cv_path_NM="@S|@2 -PlCgp"
>>>>> +      ;;
>>>>> +    esac
>>>>> +    ;;
>>>>> +  esac
>>>>>    NM=$lt_cv_path_NM
>>>>>  else
>>>>>    # Didn't find any BSD compatible name lister, look for dumpbin.
>>>>> @@ -3832,7 +3852,7 @@ fi
>>>>>  test -z "$NM" && NM=nm
>>>>>  _LT_SET_TOOL_ABI_FLAG([NM])
>>>>>  AC_SUBST([NM])
>>>>> -_LT_DECL([], [NM], [1], [A BSD- or MS-compatible name lister])dnl
>>>>> +_LT_DECL([], [NM], [1], [A BSD-, POSIX- or MS-compatible name lister])dnl
>>>>>
>>>>>  AC_CACHE_CHECK([the name lister ($NM) interface], [lt_cv_nm_interface],
>>>>>    [lt_cv_nm_interface="BSD nm"
>>>>> @@ -3847,6 +3867,8 @@ AC_CACHE_CHECK([the name lister ($NM) interface], 
>>>>> [lt_cv_nm_interface],
>>>>>    cat conftest.out >&AS_MESSAGE_LOG_FD
>>>>>    if $GREP 'External.*some_variable' conftest.out > /dev/null; then
>>>>>      lt_cv_nm_interface="MS dumpbin"
>>>>> +  elif $GREP '^[[       ]]*_*some_variable' conftest.out > /dev/null; 
>>>>> then
>>>>> +    lt_cv_nm_interface="POSIX nm"
>>>>>    fi
>>>>>    rm -f conftest*])
>>>>>  ])# LT_PATH_NM
>>>>> @@ -4012,8 +4034,33 @@ symcode='[[BCDEGRST]]'
>>>>>  # Regexp to match symbols that can be accessed directly from C.
>>>>>  sympat='\([[_A-Za-z]][[_A-Za-z0-9]]*\)'
>>>>>
>>>>> +if test "$lt_cv_nm_interface" = "MS dumpbin"; then
>>>>> +  # Gets list of data symbols to import.
>>>>> +  lt_cv_sys_global_symbol_to_import="sed -n -e 's/^I .* \(.*\)$/\1/p'"
>>>>> +  # Adjust the below global symbol transforms to fixup imported 
>>>>> variables.
>>>>> +  lt_cdecl_hook=" -e 's/^I .* \(.*\)$/extern __declspec(dllimport) char 
>>>>> \1;/p'"
>>>>> +  lt_c_name_hook=" -e 's/^I .* \(.*\)$/  {\"\1\", (void *) 0},/p'"
>>>>> +  lt_c_name_lib_hook="\
>>>>> +  -e 's/^I .* \(lib.*\)$/  {\"\1\", (void *) 0},/p'\
>>>>> +  -e 's/^I .* \(.*\)$/  {\"lib\1\", (void *) 0},/p'"
>>>>> +else
>>>>> +  # Disable hooks by default.
>>>>> +  lt_cv_sys_global_symbol_to_import=
>>>>> +  lt_cdecl_hook=
>>>>> +  lt_c_name_hook=
>>>>> +  lt_c_name_lib_hook=
>>>>> +fi
>>>>> +
>>>>>  # Define system-specific variables.
>>>>>  case $host_os in
>>>>> +aix[[4-9]]*)
>>>>> +  case `$NM -V 2>&1` in
>>>>> +  *GNU* | *'with BFD'*) ;;
>>>>> +  *)
>>>>> +    symcode='[[BDLTVWZ]]'
>>>>> +    lt_cdecl_hook=" -e 's/^W/T/p'" # weak text symbol
>>>>> +  esac
>>>>> +  ;;
>>>>>  aix*)
>>>>>    symcode='[[BCDT]]'
>>>>>    ;;
>>>>> @@ -4054,23 +4101,6 @@ case `$NM -V 2>&1` in
>>>>>    symcode='[[ABCDGIRSTW]]' ;;
>>>>>  esac
>>>>>
>>>>> -if test "$lt_cv_nm_interface" = "MS dumpbin"; then
>>>>> -  # Gets list of data symbols to import.
>>>>> -  lt_cv_sys_global_symbol_to_import="sed -n -e 's/^I .* \(.*\)$/\1/p'"
>>>>> -  # Adjust the below global symbol transforms to fixup imported 
>>>>> variables.
>>>>> -  lt_cdecl_hook=" -e 's/^I .* \(.*\)$/extern __declspec(dllimport) char 
>>>>> \1;/p'"
>>>>> -  lt_c_name_hook=" -e 's/^I .* \(.*\)$/  {\"\1\", (void *) 0},/p'"
>>>>> -  lt_c_name_lib_hook="\
>>>>> -  -e 's/^I .* \(lib.*\)$/  {\"\1\", (void *) 0},/p'\
>>>>> -  -e 's/^I .* \(.*\)$/  {\"lib\1\", (void *) 0},/p'"
>>>>> -else
>>>>> -  # Disable hooks by default.
>>>>> -  lt_cv_sys_global_symbol_to_import=
>>>>> -  lt_cdecl_hook=
>>>>> -  lt_c_name_hook=
>>>>> -  lt_c_name_lib_hook=
>>>>> -fi
>>>>> -
>>>>>  # Transform an extracted symbol line into a proper C declaration.
>>>>>  # Some systems (esp. on ia64) link data and code symbols differently,
>>>>>  # so use this general approach.
>>>>> @@ -4128,6 +4158,9 @@ for ac_symprfx in "" "_"; do
>>>>>  "     s[1]~/address@hidden/{print f,s[1],s[1]; next};"\
>>>>>  "     s[1]~prfx {split(s[1],t,\"@\"); print 
>>>>> f,t[1],substr(t[1],length(prfx))}"\
>>>>>  "     ' prfx=^$ac_symprfx]"
>>>>> +  elif test "$lt_cv_nm_interface" = "POSIX nm"; then
>>>>> +    symxfrm="\\2 $ac_symprfx\\1 \\1"
>>>>> +    lt_cv_sys_global_symbol_pipe="sed -n -e 's/^[[      
>>>>> ]]*$ac_symprfx$sympat[[         ]][[    ]]*\($symcode$symcode*\)[[      
>>>>> ]][[    ]]*.*$opt_cr$/$symxfrm/p'"
>>>>>    else
>>>>>      lt_cv_sys_global_symbol_pipe="sed -n -e 's/^.*[[    
>>>>> ]]\($symcode$symcode*\)[[       ]][[    
>>>>> ]]*$ac_symprfx$sympat$opt_cr$/$symxfrm/p'"
>>>>>    fi
>>>>> @@ -5009,19 +5042,7 @@ m4_if([$1], [CXX], [
>>>>>    _LT_TAGVAR(exclude_expsyms, 
>>>>> $1)=['_GLOBAL_OFFSET_TABLE_|_GLOBAL__F[ID]_.*']
>>>>>    case $host_os in
>>>>>    aix[[4-9]]*)
>>>>> -    # If we're using GNU nm, then we don't want the "-C" option.
>>>>> -    # -C means demangle to GNU nm, but means don't demangle to AIX nm.
>>>>> -    # Without the "-l" option, or with the "-B" option, AIX nm treats
>>>>> -    # weak defined symbols like other global defined symbols, whereas
>>>>> -    # GNU nm marks them as "W".
>>>>> -    # While the 'weak' keyword is ignored in the Export File, we need
>>>>> -    # it in the Import File for the 'aix-soname' feature, so we have
>>>>> -    # to replace the "-B" option with "-P" for AIX nm.
>>>>> -    if $NM -V 2>&1 | $GREP 'GNU' > /dev/null; then
>>>>> -      _LT_TAGVAR(export_symbols_cmds, $1)='$NM -Bpg $libobjs 
>>>>> $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == 
>>>>> "B") || (\$ 2 == "W")) && ([substr](\$ 3,1,1) != ".")) { if (\$ 2 == "W") 
>>>>> { print \$ 3 " weak" } else { print \$ 3 } } }'\'' | sort -u > 
>>>>> $export_symbols'
>>>>> -    else
>>>>> -      _LT_TAGVAR(export_symbols_cmds, $1)='`func_echo_all $NM | $SED -e 
>>>>> '\''s/B\([[^B]]*\)$/P\1/'\''` -PCpgl $libobjs $convenience | awk '\''{ if 
>>>>> (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B") || (\$ 2 == "L") || (\$ 
>>>>> 2 == "W") || (\$ 2 == "V") || (\$ 2 == "Z")) && ([substr](\$ 1,1,1) != 
>>>>> ".")) { if ((\$ 2 == "W") || (\$ 2 == "V") || (\$ 2 == "Z")) { print \$ 1 
>>>>> " weak" } else { print \$ 1 } } }'\'' | sort -u > $export_symbols'
>>>>> -    fi
>>>>> +    _LT_TAGVAR(export_symbols_cmds, $1)='$NM $libobjs $convenience | 
>>>>> $global_symbol_pipe | $EGREP -v " ($exclude_expsyms)$" | awk '\''{ kw = 
>>>>> "" } /^[[VWZ]] / { kw = " weak" } { print $ 3 kw }'\'' | sort -u > 
>>>>> $export_symbols'
>>>>>      ;;
>>>>>    pw32*)
>>>>>      _LT_TAGVAR(export_symbols_cmds, $1)=$ltdll_cmds
>>>>> @@ -5464,19 +5485,7 @@ _LT_EOF
>>>>>         exp_sym_flag='-Bexport'
>>>>>         no_entry_flag=
>>>>>        else
>>>>> -       # If we're using GNU nm, then we don't want the "-C" option.
>>>>> -       # -C means demangle to GNU nm, but means don't demangle to AIX nm.
>>>>> -       # Without the "-l" option, or with the "-B" option, AIX nm treats
>>>>> -       # weak defined symbols like other global defined symbols, whereas
>>>>> -       # GNU nm marks them as "W".
>>>>> -       # While the 'weak' keyword is ignored in the Export File, we need
>>>>> -       # it in the Import File for the 'aix-soname' feature, so we have
>>>>> -       # to replace the "-B" option with "-P" for AIX nm.
>>>>> -       if $NM -V 2>&1 | $GREP 'GNU' > /dev/null; then
>>>>> -         _LT_TAGVAR(export_symbols_cmds, $1)='$NM -Bpg $libobjs 
>>>>> $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == 
>>>>> "B") || (\$ 2 == "W")) && ([substr](\$ 3,1,1) != ".")) { if (\$ 2 == "W") 
>>>>> { print \$ 3 " weak" } else { print \$ 3 } } }'\'' | sort -u > 
>>>>> $export_symbols'
>>>>> -       else
>>>>> -         _LT_TAGVAR(export_symbols_cmds, $1)='`func_echo_all $NM | $SED 
>>>>> -e '\''s/B\([[^B]]*\)$/P\1/'\''` -PCpgl $libobjs $convenience | awk '\''{ 
>>>>> if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B") || (\$ 2 == "L") || 
>>>>> (\$ 2 == "W") || (\$ 2 == "V") || (\$ 2 == "Z")) && ([substr](\$ 1,1,1) 
>>>>> != ".")) { if ((\$ 2 == "W") || (\$ 2 == "V") || (\$ 2 == "Z")) { print 
>>>>> \$ 1 " weak" } else { print \$ 1 } } }'\'' | sort -u > $export_symbols'
>>>>> -       fi
>>>>> +       _LT_TAGVAR(export_symbols_cmds, $1)='$NM $libobjs $convenience | 
>>>>> $global_symbol_pipe | $EGREP -v " ($exclude_expsyms)$" | awk '\''{ kw = 
>>>>> "" } /^[[VWZ]] / { kw = " weak" } { print $ 3 kw }'\'' | sort -u > 
>>>>> $export_symbols'
>>>>>         aix_use_runtimelinking=no
>>>>>
>>>>>         # Test if we are trying to use run time linking or normal
>>>>> --
>>>>> 2.4.6
>>>>>



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