http://gcc.gnu.org/ml/gcc-patches/2008-10/msg00269.html

On glibc the libc.so carries a copy of the math function copysignl() but

contains unresolved symbols, any attempt to link against libgcc_s

without explicitely specifying -lm fails, resulting in a broken

bootstrap of the compiler.

diff -durN gcc-4.4.5.orig/gcc/config/t-slibgcc-elf-ver gcc-4.4.5/gcc/config/t-slibgcc-elf-ver

--- gcc-4.4.5.orig/gcc/config/t-slibgcc-elf-ver	2010-01-04 16:13:08.000000000 +0100

+++ gcc-4.4.5/gcc/config/t-slibgcc-elf-ver	2010-10-09 23:14:18.000000000 +0200

@@ -9,7 +9,7 @@

 SHLIB_OBJS = @shlib_objs@

 SHLIB_DIR = @multilib_dir@

 SHLIB_SLIBDIR_QUAL = @shlib_slibdir_qual@

-SHLIB_LC = -lc

+SHLIB_LC = @libgcc_libm@ -lc

 SHLIB_MAKE_SOLINK = $(LN_S) $(SHLIB_SONAME) $(SHLIB_DIR)/$(SHLIB_SOLINK)

 SHLIB_INSTALL_SOLINK = $(LN_S) $(SHLIB_SONAME) \

 	$$(DESTDIR)$$(slibdir)$(SHLIB_SLIBDIR_QUAL)/$(SHLIB_SOLINK)

diff -durN gcc-4.4.5.orig/libgcc/configure gcc-4.4.5/libgcc/configure

--- gcc-4.4.5.orig/libgcc/configure	2008-11-20 18:13:01.000000000 +0100

+++ gcc-4.4.5/libgcc/configure	2010-10-09 23:14:18.000000000 +0200

@@ -272,7 +272,7 @@

 PACKAGE_BUGREPORT=''

 ac_unique_file="static-object.mk"

-ac_subst_vars='SHELL PATH_SEPARATOR PACKAGE_NAME PACKAGE_TARNAME PACKAGE_VERSION PACKAGE_STRING PACKAGE_BUGREPORT exec_prefix prefix program_transform_name bindir sbindir libexecdir datadir sysconfdir sharedstatedir localstatedir libdir includedir oldincludedir infodir mandir build_alias host_alias target_alias DEFS ECHO_C ECHO_N ECHO_T LIBS libgcc_topdir enable_shared slibdir INSTALL_PROGRAM INSTALL_SCRIPT INSTALL_DATA AWK build build_cpu build_vendor build_os host host_cpu host_vendor host_os host_noncanonical build_libsubdir build_subdir host_subdir target_subdir AR ac_ct_AR LIPO ac_ct_LIPO NM ac_ct_NM RANLIB ac_ct_RANLIB STRIP ac_ct_STRIP LN_S CC CFLAGS LDFLAGS CPPFLAGS ac_ct_CC EXEEXT OBJEXT CPP decimal_float enable_decimal_float fixed_point vis_hide set_have_cc_tls tmake_file extra_parts asm_hidden_op LIBOBJS LTLIBOBJS'

+ac_subst_vars='SHELL PATH_SEPARATOR PACKAGE_NAME PACKAGE_TARNAME PACKAGE_VERSION PACKAGE_STRING PACKAGE_BUGREPORT exec_prefix prefix program_transform_name bindir sbindir libexecdir datadir sysconfdir sharedstatedir localstatedir libdir includedir oldincludedir infodir mandir build_alias host_alias target_alias DEFS ECHO_C ECHO_N ECHO_T LIBS libgcc_topdir enable_shared slibdir INSTALL_PROGRAM INSTALL_SCRIPT INSTALL_DATA AWK build build_cpu build_vendor build_os host host_cpu host_vendor host_os host_noncanonical build_libsubdir build_subdir host_subdir target_subdir AR ac_ct_AR LIPO ac_ct_LIPO NM ac_ct_NM RANLIB ac_ct_RANLIB STRIP ac_ct_STRIP LN_S CC CFLAGS LDFLAGS CPPFLAGS ac_ct_CC EXEEXT OBJEXT CPP decimal_float enable_decimal_float fixed_point vis_hide set_have_cc_tls LIBGCC_LIBM tmake_file extra_parts asm_hidden_op LIBOBJS LTLIBOBJS'

 ac_subst_files=''

 ac_pwd=`pwd`

@@ -3547,6 +3547,39 @@

 fi

+# On powerpc libgcc_s references copysignl which is a libm function but

+# glibc apparently also provides it via libc as opposed to uClibc where

+# it lives in libm.

+echo "$as_me:$LINENO: checking for library containing copysignl" >&5

+echo $ECHO_N "checking for library containing copysignl... $ECHO_C" >&6

+if test "${libgcc_cv_copysignl_lib+set}" = set; then

+  echo $ECHO_N "(cached) $ECHO_C" >&6

+else

+

+    echo '#include <features.h>' > conftest.c

+    echo 'int the_libc = __UCLIBC__ + __powerpc__;' >> conftest.c

+    libgcc_cv_copysignl_lib="-lc"

+    if { ac_try='${CC-cc} -S conftest.c -o conftest.s 1>&5'

+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5

+  (eval $ac_try) 2>&5

+  ac_status=$?

+  echo "$as_me:$LINENO: \$? = $ac_status" >&5

+  (exit $ac_status); }; }

+    then

+	libgcc_cv_copysignl_lib="-lm"

+    fi

+    rm -f conftest.*

+

+fi

+echo "$as_me:$LINENO: result: $libgcc_cv_copysignl_lib" >&5

+echo "${ECHO_T}$libgcc_cv_copysignl_lib" >&6

+

+case /${libgcc_cv_copysignl_lib}/ in

+  /-lm/) LIBGCC_LIBM="$LIBGCC_LIBM -lm" ;;

+  *) LIBGCC_LIBM= ;;

+esac

+

+

 # Conditionalize the makefile for this target machine.

 tmake_file_=

 for f in ${tmake_file}

@@ -4267,6 +4300,7 @@

 s,@fixed_point@,$fixed_point,;t t

 s,@vis_hide@,$vis_hide,;t t

 s,@set_have_cc_tls@,$set_have_cc_tls,;t t

+s,@LIBGCC_LIBM@,$LIBGCC_LIBM,;t t

 s,@tmake_file@,$tmake_file,;t t

 s,@extra_parts@,$extra_parts,;t t

 s,@asm_hidden_op@,$asm_hidden_op,;t t

diff -durN gcc-4.4.5.orig/libgcc/configure.ac gcc-4.4.5/libgcc/configure.ac

--- gcc-4.4.5.orig/libgcc/configure.ac	2008-11-20 18:13:01.000000000 +0100

+++ gcc-4.4.5/libgcc/configure.ac	2010-10-09 23:14:18.000000000 +0200

@@ -223,6 +223,27 @@

 fi

 AC_SUBST(set_have_cc_tls)

+# On powerpc libgcc_s references copysignl which is a libm function but

+# glibc apparently also provides it via libc as opposed to uClibc where

+# it lives in libm.

+AC_CACHE_CHECK

+  libgcc_cv_copysignl_lib,

+    echo '#include <features.h>' > conftest.c

+    echo 'int the_libc = __UCLIBC__ + __powerpc__;' >> conftest.c

+    libgcc_cv_copysignl_lib="-lc"

+    if AC_TRY_COMMAND(${CC-cc} -S conftest.c -o conftest.s 1>&AS_MESSAGE_LOG_FD)

+    then

+	libgcc_cv_copysignl_lib="-lm"

+    fi

+    rm -f conftest.*

+  ])

+

+case /${libgcc_cv_copysignl_lib}/ in

+  /-lm/) LIBGCC_LIBM="$LIBGCC_LIBM -lm" ;;

+  *) LIBGCC_LIBM= ;;

+esac

+AC_SUBST(LIBGCC_LIBM)

+

 # Conditionalize the makefile for this target machine.

 tmake_file_=

 for f in ${tmake_file}

diff -durN gcc-4.4.5.orig/libgcc/Makefile.in gcc-4.4.5/libgcc/Makefile.in

--- gcc-4.4.5.orig/libgcc/Makefile.in	2009-04-10 01:23:07.000000000 +0200

+++ gcc-4.4.5/libgcc/Makefile.in	2010-10-09 23:14:18.000000000 +0200

@@ -39,6 +39,7 @@

 decimal_float = @decimal_float@

 enable_decimal_float = @enable_decimal_float@

 fixed_point = @fixed_point@

+LIBGCC_LIBM = @LIBGCC_LIBM@

 host_noncanonical = @host_noncanonical@

@@ -787,9 +788,10 @@

 		@multilib_dir@,$(MULTIDIR),$(subst \

 		@shlib_objs@,$(objects),$(subst \

 		@shlib_base_name@,libgcc_s,$(subst \

+		@libgcc_libm@,$(LIBGCC_LIBM),$(subst \

 		@shlib_map_file@,$(mapfile),$(subst \

 		@shlib_slibdir_qual@,$(MULTIOSSUBDIR),$(subst \

-		@shlib_slibdir@,$(shlib_slibdir),$(SHLIB_LINK))))))))

+		@shlib_slibdir@,$(shlib_slibdir),$(SHLIB_LINK)))))))))

 libunwind$(SHLIB_EXT): $(libunwind-s-objects) $(extra-parts)

 	# @multilib_flags@ is still needed because this may use