On 2016-03-11 22:22, Michael Haubenwallner wrote:
> Hi Peter,
>
> thanks for looking at the patch!
>
> On 03/10/2016 12:29 PM, Peter Rosin wrote:
>> Hi Michael,
>>
>> I had a look since I wrote a patch for POSIX nm a couple of years ago
>> that I never submitted (I didn't see any use case) which looked very
>> similar, excepting the AIX-ism in your version.
>>
>> On 2016-03-10 10:01, Michael Haubenwallner 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 "$NM"; then
>>> # Let the user override the test.
>>> lt_cv_path_NM=$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 `@S|@2 -V 2>&1` in
>>> + *GNU* | *'with BFD'*)
>>> + lt_cv_path_NM="@S|@2 -Bgp"
>>> + ;;
>>> + *)
>>> + lt_cv_path_NM="@S|@2 -PlCgp"
>>> + ;;
>>> + esac
>>> + ;;
>>> + esac
>>
>> You are overriding the user provided $NM. Not good. If a user says
>> NM="nm --this-will-not-work", then you will have to trust that even if
>> it is not likely to work. User error, so what? Adding -Bgp or -PlCgp
>> can only be done when the user has not specified $NM.
>
> Agreed. I've added a check whether NM will mark weak symbols instead.
I was thinking that you needed to try various flags for each nm in the
mentioned loop until you find a good nm/flags combo, and keep looking if you
think you might find an even better combo later (i.e. what is there today,
where a BSD nm is preferred over other name listers, but tweaked to suite
AIX which seemingly prefers posix nm above all else).
Then, when you have found an nm/flags combo (or if the user has provided
it), and this part was already ok in the patch, you make libtool detect if
the $NM interface is posix, bsd, MS dumpbin or ..., and build the symbol
pipe accordingly.
>> Yes, I see that
>> AIX has previously added nm flags behind the back of the user, but there
>> is no reason to continue with that now that you are changing things.
>>
>> You need to modify innards of the lt_tmp_nm loop in the else branch
>> a few lines up (just above the context).
>>
>>> NM=$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"
>>
>> Isn't this a pretty weak check, perhaps append ' B' and remove the
>> possibility
>> for leading whitespace? (see my last comment below for reasoning on spaces)
>
> As long as the expected symbol name comes first, isn't it POSIX then?
> Anyway, 've added "[\t ][\t ]*[A-Za-z]" now, as $symcode is defined later.
> And there is no check for BSD style after all.
Since it is POSIX output, my point is that it should be fairly safe to assume
B as the symbol type, maybe it could be a D if the tools do not put zero-vars
in bss, but why wouldn't they? So, perhaps [BD] is a more palatable pattern?
I simply don't think you need to match every possible symbol type. Do you?
>>
>>> 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
>>> + ;;
>>
>> Why does AIX need to export weak symbols, when W symbols are not
>> handled in the nm output on other systems? This seems inconsistent?
>
> Erm, with GNU nm, $symcode actually does contain W. And a weak symbol
> is referenced as variable in the lt_*_LTX_preloaded_symbols array,
> even if it might actually be a text symbol... What do I miss here?
It probably me missing something, like looking at the default symcodes
instead of the GNU nm symcodes. My bad.
> Why there is need for the weakness information: The aix-soname=svr4
> feature uses Import Files to provide filename-based shared library
> versioning, so a subsequent linker does actually link against a text
> file rather than some binary shared object. And the Import File allows
> to specify the weak keyword, while it is ignored in an Export File.
> So the content of the Export File used to create a shared library is
> provided as the Import File needed to link against that shared library.
Ok, I clearly don't know this area, I was just asking because I thought
I saw an inconsistency. I guess it is ok on other systems, and if not I
guess that is not really your responsibility. Sorry for the noise...
>>
>>> aix*)
>>> symcode='[[BCDT]]'
>>> ;;
>>> @@ -4054,23 +4101,6 @@ case `$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 .* \(.*\)$/ {\"lib\1\", (void *) 0},/p'"
>>> -else
>>> - # Disable hooks by default.
>>> - lt_cv_sys_global_symbol_to_import=
>>> - lt_cdecl_hook=
>>> - lt_c_name_hook=
>>> - lt_c_name_lib_hook=
>>> -fi
>>> -
>>> # Transform an extracted symbol line into a proper C declaration.
>>> # Some systems (esp. on ia64) link data and code symbols differently,
>>> # so use this general approach.
>>> @@ -4128,6 +4158,9 @@ for ac_symprfx in "" "_"; do
>>> " s[1]~/^[@?]/{print f,s[1],s[1]; next};"\
>>> " s[1]~prfx {split(s[1],t,\"@\"); print
>>> f,t[1],substr(t[1],length(prfx))}"\
>>> " ' prfx=^$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'"
>>
>> Do you really need to handle leading and multiple whitespace here?
>> Posix, at least as seen here
>> http://pubs.opengroup.org/onlinepubs/009696699/utilities/nm.html
>> seems quite clear on no leading space and one space only as separator.
>
> Must admit that I haven't looked at the specs - and except for leading
> ones, AIX nm does write multiple whitespaces between the fields.
Eric cleared that up, I was wrong. Sorry for the noise.
>>> 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]]*)export_symbols_cmds
>>> - # 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'
>
> On a side note:
> As the C++ value is identical to the C one for various platforms,
> wouldn't it work for them to do something like:
> _LT_TAGVAR(export_symbols_cmds, $1)=$_LT_TAGVAR(export_symbols_cmds)
> _LT_TAGVAR(exclude_expsyms, $1)=$_LT_TAGVAR(exclude_expsyms)
Would you not need to change tag between the get and the set for that
to work as I think you intend? What am I missing?
>>> ;;
>>> 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'
>
> The main motivation here is this simplification after all,
> as this needs another symbol exclusion (patch 4/4), which
> does make sense for the preloaded symbols list as well.
Yes, it is much cleaner to adjust the symbol pipe according to $NM, than
trying to "fix" $NM by adding flags. That part is nice indeed!
Cheers,
Peter
