Bring back nocombreloc if dumping

Without this patch, Emacs dumps core on Fedora 28 x86-64
when configured via "CC='gcc -m32' --enable-gcc-warnings
--without-imagemagick --without-gif --with-modules
PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig:/usr/share/pkgconfig".
and then when run normally in a windowing system.
'make check' and 'emacs -nw' work OK even without the patch.
* configure.ac (LD_SWITCH_SYSTEM_TEMACS): Prepend
-znocombreloc if supported and if dumping.  This mostly
reverts 2018-06-15T21:37:39!eggert@cs.ucla.edu "Remove old
combreloc hack".

diff --git a/configure.ac b/configure.ac
index bfd9d5d177c4afb038dad92d02ebee0887fd8147..3a610909026a4a49dd9be813ed9a2c580bc61bcd 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1336,6 +1336,37 @@ else
     ac_link="$ac_link $NON_GCC_LINK_TEST_OPTIONS"
 fi
 
+dnl On some platforms using GNU ld, linking temacs needs -znocombreloc.
+dnl Although this has something to do with dumping, the details are unknown.
+dnl If the flag is used but not needed,
+dnl Emacs should still work (albeit a bit more slowly),
+dnl so use the flag everywhere that it is supported.
+dnl When testing whether the flag works, treat GCC specially
+dnl since it just gives a non-fatal 'unrecognized option'
+dnl if not built to support GNU ld.
+if test "$GCC" = yes; then
+  LDFLAGS_NOCOMBRELOC="-Wl,-znocombreloc"
+else
+  LDFLAGS_NOCOMBRELOC="-znocombreloc"
+fi
+
+AC_CACHE_CHECK([for -znocombreloc], [emacs_cv_znocombreloc],
+  [if test "$CANNOT_DUMP" = "yes"; then
+     emacs_cv_znocombreloc='not needed'
+   else
+     save_LDFLAGS=$LDFLAGS
+     LDFLAGS="$LDFLAGS $LDFLAGS_NOCOMBRELOC"
+     AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
+       [emacs_cv_znocombreloc=yes], [emacs_cv_znocombreloc=no])
+     LDFLAGS=$save_LDFLAGS
+   fi])
+
+case $emacs_cv_znocombreloc in
+  no*)
+    LDFLAGS_NOCOMBRELOC= ;;
+esac
+
+
 AC_CACHE_CHECK([whether addresses are sanitized],
   [emacs_cv_sanitize_address],
   [AC_COMPILE_IFELSE(
@@ -5346,6 +5377,8 @@ if test x$ac_enable_profiling != x ; then
   esac
 fi
 
+LD_SWITCH_SYSTEM_TEMACS="$LDFLAGS_NOCOMBRELOC $LD_SWITCH_SYSTEM_TEMACS"
+
 AC_SUBST(LD_SWITCH_SYSTEM_TEMACS)
 
 ## Common for all window systems

diff --git a/etc/PROBLEMS b/etc/PROBLEMS
index eba3420fcb8a6857d3f18b803b9a238e3ad8c898..6805e8733d52f1704106c7cd37cb83ad7805595d 100644 (file)
--- a/etc/PROBLEMS
+++ b/etc/PROBLEMS
@@ -192,6 +192,18 @@ Upgrading to a newer version of Exceed has been reported to prevent
 these crashes.  You should consider switching to a free X server, such
 as Xming or Cygwin/X.
 
+** Emacs crashes with SIGSEGV in XtInitializeWidgetClass.
+
+It crashes on X, but runs fine when called with option "-nw".
+
+This has been observed when Emacs is linked with GNU ld but without passing
+the -z nocombreloc flag.  Emacs normally knows to pass the -z nocombreloc
+flag when needed, so if you come across a situation where the flag is
+necessary but missing, please report it via M-x report-emacs-bug.
+
+On platforms such as Solaris, you can also work around this problem by
+configuring your compiler to use the native linker instead of GNU ld.
+
 ** When Emacs is compiled with Gtk+, closing a display kills Emacs.
 
 There is a long-standing bug in GTK that prevents it from recovering