On 7/1/22 09:20, Fangrui Song via Gcc-patches wrote:
> On 2022-07-01, Andrew Pinski wrote:
>> On Thu, Jun 30, 2022 at 11:58 PM Fangrui Song via Gcc-patches
>> <gcc-patches@gcc.gnu.org> wrote:
>>>
>>> From: Fangrui Song <i...@maskray.me>
>>>
>>> SHF_COMPRESSED style zlib has been supported since binutils 2.26
>>> and the legacy zlib-gnu option hasn't gain adoption.
>>> According to Debian Code Search (`gz=zlib-gnu`), no project uses
>>> -gz=zlib-gnu (valgrind has a configure to use -gz=zlib).
>>> Remove support for the legacy zlib-gnu and simplify configure.ac by
>>> removing zlib-gnu ld/as check.
>>
>> A couple of things, you are missing a changelog.
>
> Sorry.
>
>> Second, why remove something which is still working?
Hi.
I do support the option removal, while I would replace the removal with a
warning
saying no compression will be used.
>
> It's unused and its existence causes confusion: the paradox of choice.
> People may assume the support may be good but newer DWARF consumers may
> not support the legacy format.
Agree, the compression format is legacy. I verified all openSUSE packages (15k)
and there's no project actively using it.
>
> The other motivation is to clean up it a bit. I foresee that someone
> will add --compress-debug-sections=zstd to binutils and configure.ac and
> gcc/gcc.cc would become more messy.
The argument makes sense, it will be even bigger mess.
@Richi: Is it something we can deprecate for GCC 13?
Martin
>
>> Third, why not just make gz=zlib-gnu as an alias to gz=zlib instead so
>> if someone used it before it will still work. we try not to remove
>> options; have them emit a warning and be ignored (or moved over to the
>> closed option).
>
> Changing the semantics of -gz=zlib-gnu would be even more confusing.
>
>> Thanks,
>> Andrew
>>
>>> ---
>>> gcc/common.opt | 3 ---
>>> gcc/configure | 33 ++++++---------------------------
>>> gcc/configure.ac | 29 ++++-------------------------
>>> gcc/doc/invoke.texi | 11 +++++------
>>> gcc/gcc.cc | 22 ++--------------------
>>> 5 files changed, 17 insertions(+), 81 deletions(-)
>>>
>>> diff --git a/gcc/common.opt b/gcc/common.opt
>>> index e7a51e882ba..8754d93d545 100644
>>> --- a/gcc/common.opt
>>> +++ b/gcc/common.opt
>>> @@ -3424,9 +3424,6 @@ Enum(compressed_debug_sections) String(none) Value(0)
>>> EnumValue
>>> Enum(compressed_debug_sections) String(zlib) Value(1)
>>>
>>> -EnumValue
>>> -Enum(compressed_debug_sections) String(zlib-gnu) Value(2)
>>> -
>>> gz
>>> Common Driver
>>> Generate compressed debug sections.
>>> diff --git a/gcc/configure b/gcc/configure
>>> index 62872d132ea..ca87e875e9d 100755
>>> --- a/gcc/configure
>>> +++ b/gcc/configure
>>> @@ -19674,7 +19674,7 @@ else
>>> lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
>>> lt_status=$lt_dlunknown
>>> cat > conftest.$ac_ext <<_LT_EOF
>>> -#line 19679 "configure"
>>> +#line 19677 "configure"
>>> #include "confdefs.h"
>>>
>>> #if HAVE_DLFCN_H
>>> @@ -19780,7 +19780,7 @@ else
>>> lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
>>> lt_status=$lt_dlunknown
>>> cat > conftest.$ac_ext <<_LT_EOF
>>> -#line 19785 "configure"
>>> +#line 19783 "configure"
>>> #include "confdefs.h"
>>>
>>> #if HAVE_DLFCN_H
>>> @@ -29711,20 +29711,13 @@ else
>>> if $gcc_cv_as --compress-debug-sections -o conftest.o conftest.s 2>&1 |
>>> grep -i warning > /dev/null
>>> then
>>> gcc_cv_as_compress_debug=0
>>> - # Since binutils 2.26, gas supports --compress-debug-sections=type,
>>> + # Since binutils 2.26, gas supports --compress-debug-sections=zlib,
>>> # defaulting to the ELF gABI format.
>>> - elif $gcc_cv_as --compress-debug-sections=zlib-gnu -o conftest.o
>>> conftest.s > /dev/null 2>&1
>>> + elif $gcc_cv_as --compress-debug-sections=zlib -o conftest.o conftest.s
>>> > /dev/null 2>&1
>>> then
>>> gcc_cv_as_compress_debug=2
>>> gcc_cv_as_compress_debug_option="--compress-debug-sections"
>>> gcc_cv_as_no_compress_debug_option="--nocompress-debug-sections"
>>> - # Before binutils 2.26, gas only supported --compress-debug-options and
>>> - # emitted the traditional GNU format.
>>> - elif $gcc_cv_as --compress-debug-sections -o conftest.o conftest.s >
>>> /dev/null 2>&1
>>> - then
>>> - gcc_cv_as_compress_debug=1
>>> - gcc_cv_as_compress_debug_option="--compress-debug-sections"
>>> - gcc_cv_as_no_compress_debug_option="--nocompress-debug-sections"
>>> else
>>> gcc_cv_as_compress_debug=0
>>> fi
>>> @@ -30238,42 +30231,28 @@ $as_echo "$gcc_cv_ld_eh_gc_sections_bug" >&6; }
>>>
>>> { $as_echo "$as_me:${as_lineno-$LINENO}: checking linker for compressed
>>> debug sections" >&5
>>> $as_echo_n "checking linker for compressed debug sections... " >&6; }
>>> -# gold/gld support compressed debug sections since binutils 2.19/2.21
>>> -# In binutils 2.26, gld gained support for the ELF gABI format.
>>> +# GNU ld/gold support --compressed-debug-sections=zlib since binutils 2.26.
>>> if test $in_tree_ld = yes ; then
>>> gcc_cv_ld_compress_debug=0
>>> if test $ld_is_mold = yes; then
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> - elif test "$gcc_cv_gld_major_version" -eq 2 -a
>>> "$gcc_cv_gld_minor_version" -ge 19 -o "$gcc_cv_gld_major_version" -gt 2 \
>>> - && test $in_tree_ld_is_elf = yes && test $ld_is_gold = yes; then
>>> - gcc_cv_ld_compress_debug=2
>>> - gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> elif test "$gcc_cv_gld_major_version" -eq 2 -a
>>> "$gcc_cv_gld_minor_version" -ge 26 -o "$gcc_cv_gld_major_version" -gt 2 \
>>> && test $in_tree_ld_is_elf = yes && test $ld_is_gold = no; then
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> - elif test "$gcc_cv_gld_major_version" -eq 2 -a
>>> "$gcc_cv_gld_minor_version" -ge 21 -o "$gcc_cv_gld_major_version" -gt 2 \
>>> - && test $in_tree_ld_is_elf = yes; then
>>> - gcc_cv_ld_compress_debug=1
>>> fi
>>> elif echo "$ld_ver" | grep GNU > /dev/null; then
>>> if test $ld_is_mold = yes; then
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> elif test "$ld_vers_major" -lt 2 \
>>> - || test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -lt 21; then
>>> + || test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -lt 26; then
>>> gcc_cv_ld_compress_debug=0
>>> - elif test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -lt 26; then
>>> - gcc_cv_ld_compress_debug=1
>>> else
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> fi
>>> - if test $ld_is_gold = yes; then
>>> - gcc_cv_ld_compress_debug=2
>>> - gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> - fi
>>> else
>>> case "${target}" in
>>> *-*-solaris2*)
>>> diff --git a/gcc/configure.ac b/gcc/configure.ac
>>> index 446747311a6..f40f75271c2 100644
>>> --- a/gcc/configure.ac
>>> +++ b/gcc/configure.ac
>>> @@ -5733,20 +5733,13 @@ gcc_GAS_CHECK_FEATURE([compressed debug sections],
>>> if $gcc_cv_as --compress-debug-sections -o conftest.o conftest.s 2>&1 |
>>> grep -i warning > /dev/null
>>> then
>>> gcc_cv_as_compress_debug=0
>>> - # Since binutils 2.26, gas supports --compress-debug-sections=type,
>>> + # Since binutils 2.26, gas supports --compress-debug-sections=zlib,
>>> # defaulting to the ELF gABI format.
>>> - elif $gcc_cv_as --compress-debug-sections=zlib-gnu -o conftest.o
>>> conftest.s > /dev/null 2>&1
>>> + elif $gcc_cv_as --compress-debug-sections=zlib -o conftest.o conftest.s
>>> > /dev/null 2>&1
>>> then
>>> gcc_cv_as_compress_debug=2
>>> gcc_cv_as_compress_debug_option="--compress-debug-sections"
>>> gcc_cv_as_no_compress_debug_option="--nocompress-debug-sections"
>>> - # Before binutils 2.26, gas only supported --compress-debug-options and
>>> - # emitted the traditional GNU format.
>>> - elif $gcc_cv_as --compress-debug-sections -o conftest.o conftest.s >
>>> /dev/null 2>&1
>>> - then
>>> - gcc_cv_as_compress_debug=1
>>> - gcc_cv_as_compress_debug_option="--compress-debug-sections"
>>> - gcc_cv_as_no_compress_debug_option="--nocompress-debug-sections"
>>> else
>>> gcc_cv_as_compress_debug=0
>>> fi])
>>> @@ -6131,42 +6124,28 @@ fi
>>> AC_MSG_RESULT($gcc_cv_ld_eh_gc_sections_bug)
>>>
>>> AC_MSG_CHECKING(linker for compressed debug sections)
>>> -# gold/gld support compressed debug sections since binutils 2.19/2.21
>>> -# In binutils 2.26, gld gained support for the ELF gABI format.
>>> +# GNU ld/gold support --compressed-debug-sections=zlib since binutils 2.26.
>>> if test $in_tree_ld = yes ; then
>>> gcc_cv_ld_compress_debug=0
>>> if test $ld_is_mold = yes; then
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> - elif test "$gcc_cv_gld_major_version" -eq 2 -a
>>> "$gcc_cv_gld_minor_version" -ge 19 -o "$gcc_cv_gld_major_version" -gt 2 \
>>> - && test $in_tree_ld_is_elf = yes && test $ld_is_gold = yes; then
>>> - gcc_cv_ld_compress_debug=2
>>> - gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> elif test "$gcc_cv_gld_major_version" -eq 2 -a
>>> "$gcc_cv_gld_minor_version" -ge 26 -o "$gcc_cv_gld_major_version" -gt 2 \
>>> && test $in_tree_ld_is_elf = yes && test $ld_is_gold = no; then
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> - elif test "$gcc_cv_gld_major_version" -eq 2 -a
>>> "$gcc_cv_gld_minor_version" -ge 21 -o "$gcc_cv_gld_major_version" -gt 2 \
>>> - && test $in_tree_ld_is_elf = yes; then
>>> - gcc_cv_ld_compress_debug=1
>>> fi
>>> elif echo "$ld_ver" | grep GNU > /dev/null; then
>>> if test $ld_is_mold = yes; then
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> elif test "$ld_vers_major" -lt 2 \
>>> - || test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -lt 21; then
>>> + || test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -lt 26; then
>>> gcc_cv_ld_compress_debug=0
>>> - elif test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -lt 26; then
>>> - gcc_cv_ld_compress_debug=1
>>> else
>>> gcc_cv_ld_compress_debug=3
>>> gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> fi
>>> - if test $ld_is_gold = yes; then
>>> - gcc_cv_ld_compress_debug=2
>>> - gcc_cv_ld_compress_debug_option="--compress-debug-sections"
>>> - fi
>>> else
>>> changequote(,)dnl
>>> case "${target}" in
>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>> index 757775ea576..467659cb094 100644
>>> --- a/gcc/doc/invoke.texi
>>> +++ b/gcc/doc/invoke.texi
>>> @@ -10775,12 +10775,11 @@ location views are enabled.
>>> Produce compressed debug sections in DWARF format, if that is supported.
>>> If @var{type} is not given, the default type depends on the capabilities
>>> of the assembler and linker used. @var{type} may be one of
>>> -@samp{none} (don't compress debug sections), @samp{zlib} (use zlib
>>> -compression in ELF gABI format), or @samp{zlib-gnu} (use zlib
>>> -compression in traditional GNU format). If the linker doesn't support
>>> -writing compressed debug sections, the option is rejected. Otherwise,
>>> -if the assembler does not support them, @option{-gz} is silently ignored
>>> -when producing object files.
>>> +@samp{none} (don't compress debug sections), or @samp{zlib} (use zlib
>>> +compression in ELF gABI format). If the linker doesn't support writing
>>> +compressed debug sections, the option is rejected. Otherwise, if the
>>> +assembler does not support them, @option{-gz} is silently ignored when
>>> +producing object files.
>>>
>>> @item -femit-struct-debug-baseonly
>>> @opindex femit-struct-debug-baseonly
>>> diff --git a/gcc/gcc.cc b/gcc/gcc.cc
>>> index 5cbb38560b2..660cd6f4ef4 100644
>>> --- a/gcc/gcc.cc
>>> +++ b/gcc/gcc.cc
>>> @@ -827,22 +827,11 @@ proper position among the other output files. */
>>> /* No linker support. */
>>> #define LINK_COMPRESS_DEBUG_SPEC \
>>> " %{gz*:%e-gz is not supported in this configuration} "
>>> -#elif HAVE_LD_COMPRESS_DEBUG == 1
>>> -/* GNU style on input, GNU ld options. Reject, not useful. */
>>> -#define LINK_COMPRESS_DEBUG_SPEC \
>>> - " %{gz*:%e-gz is not supported in this configuration} "
>>> -#elif HAVE_LD_COMPRESS_DEBUG == 2
>>> -/* GNU style, GNU gold options. */
>>> -#define LINK_COMPRESS_DEBUG_SPEC \
>>> - " %{gz|gz=zlib-gnu:" LD_COMPRESS_DEBUG_OPTION "=zlib}" \
>>> - " %{gz=none:" LD_COMPRESS_DEBUG_OPTION "=none}" \
>>> - " %{gz=zlib:%e-gz=zlib is not supported in this configuration} "
>>> #elif HAVE_LD_COMPRESS_DEBUG == 3
>>> /* ELF gABI style. */
>>> #define LINK_COMPRESS_DEBUG_SPEC \
>>> " %{gz|gz=zlib:" LD_COMPRESS_DEBUG_OPTION "=zlib}" \
>>> - " %{gz=none:" LD_COMPRESS_DEBUG_OPTION "=none}" \
>>> - " %{gz=zlib-gnu:" LD_COMPRESS_DEBUG_OPTION "=zlib-gnu} "
>>> + " %{gz=none:" LD_COMPRESS_DEBUG_OPTION "=none}"
>>> #else
>>> #error Unknown value for HAVE_LD_COMPRESS_DEBUG.
>>> #endif
>>> @@ -891,18 +880,11 @@ proper position among the other output files. */
>>> /* No assembler support. Ignore silently. */
>>> #define ASM_COMPRESS_DEBUG_SPEC \
>>> " %{gz*:} "
>>> -#elif HAVE_AS_COMPRESS_DEBUG == 1
>>> -/* GNU style, GNU as options. */
>>> -#define ASM_COMPRESS_DEBUG_SPEC \
>>> - " %{gz|gz=zlib-gnu:" AS_COMPRESS_DEBUG_OPTION "}" \
>>> - " %{gz=none:" AS_NO_COMPRESS_DEBUG_OPTION "}" \
>>> - " %{gz=zlib:%e-gz=zlib is not supported in this configuration} "
>>> #elif HAVE_AS_COMPRESS_DEBUG == 2
>>> /* ELF gABI style. */
>>> #define ASM_COMPRESS_DEBUG_SPEC \
>>> " %{gz|gz=zlib:" AS_COMPRESS_DEBUG_OPTION "=zlib}" \
>>> - " %{gz=none:" AS_COMPRESS_DEBUG_OPTION "=none}" \
>>> - " %{gz=zlib-gnu:" AS_COMPRESS_DEBUG_OPTION "=zlib-gnu} "
>>> + " %{gz=none:" AS_COMPRESS_DEBUG_OPTION "=none}"
>>> #else
>>> #error Unknown value for HAVE_AS_COMPRESS_DEBUG.
>>> #endif
>>> --
>>> 2.37.0.rc0.161.g10f37bed90-goog
>>>
