Re: [PATCH] Remove legacy -gz=zlib-gnu

Fri, 01 Jul 2022 00:21:15 -0700 

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?


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.

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.


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























					Reply via email to