Simplify data_start configuration.

This is a followon simplification to the fix for Bug#13650.
* admin/CPP-DEFINES (DATA_START, ORDINARY_LINK): Remove.
* configure.ac (CRT_DIR, LIB_STANDARD, START_FILES, DATA_START)
(LD_FIRSTFLAG, ORDINARY_LINK, LIB_GCC): Remove.
(AC_CHECK_HEADERS_ONCE): Remove sys/resource.h, as it's
not always needed.
(HAVE_DATA_START): New macro.
* etc/PROBLEMS (LIBS_SYSTEM, LIBS_MACHINE, LIBS_STANDARD): Remove.
Remove legacy-systems section, as this stuff is no longer
applicable with current linking strategies.
* src/Makefile.in (LD_FIRSTFLAG, LIB_GCC, CRT_DIR, LIB_STANDARD)
(START_FILES): Remove.  All uses removed.
(otherobj): Remove $(VMLIMIT_OBJ), as it's now first.
(ALLOBJS): Move here from autodeps.mk, and with VMLIMITS_OBJ first.
(buildobj.h): Use it.
($(ALLOBJS)): Depend on globals.h.
(temacs$(EXEEXT)): Use $(ALLOBJS).
* src/autodeps.mk (ALLOBJS): Move to Makefile.in.
* src/deps.mk (vm-limit.o):
* src/makefile.w32-in ($(BLD)/vm-limit.$(O)):
Do not depend on mem-limits.h.
* src/emacs.c (__do_global_ctors, __do_global_ctors_aux)
(__do_global_dtors, __CTOR_LIST__, __DTOR_LIST__)
[__GNUC__ && !ORDINARY_LINK]: Remove.
* src/mem-limits.h, src/pre-crt0.c: Remove.
* src/unexaix.c, src/unexcoff.c: Don't include mem-limits.h.
* src/unexcoff.c (etext): New decl.
(make_hdr): Use it instead of start_of_data.
* src/vm-limit.c: Move most of mem-limits.h's contents here.
(data_start): New decl.  It's OK if this is approximate,
so simplify-away some unnecessary exactness.
(POINTER): Remove; all uses removed.
(data_space_start): Now char *, to avoid casts.
(exceeds_lisp_ptr): New function, replacing the old
EXCEEDS_LISP_PTR macro.  All uses changed.
(check_memory_limits): Simplify and remove casts.
(start_of_data) [!CANNOT_DUMP || !SYSTEM_MALLOC]: Remove.
(memory_warnings): Use data_start instead of start_of_data.

Fixes: debbugs:13783

11 files changed, 95 insertions, 164 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 8d3fc1e56fb..00d1f30dd46 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,36 @@
+2013-02-25  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Simplify data_start configuration (Bug#13783).
+        This is a followon simplification to the fix for Bug#13650.
+        * Makefile.in (LD_FIRSTFLAG, LIB_GCC, CRT_DIR, LIB_STANDARD)
+        (START_FILES): Remove.  All uses removed.
+        (otherobj): Remove $(VMLIMIT_OBJ), as it's now first.
+        (ALLOBJS): Move here from autodeps.mk, and with VMLIMITS_OBJ first.
+        (buildobj.h): Use it.
+        ($(ALLOBJS)): Depend on globals.h.
+        (temacs$(EXEEXT)): Use $(ALLOBJS).
+        * autodeps.mk (ALLOBJS): Move to Makefile.in.
+        * deps.mk (vm-limit.o):
+        * makefile.w32-in ($(BLD)/vm-limit.$(O)):
+        Do not depend on mem-limits.h.
+        * emacs.c (__do_global_ctors, __do_global_ctors_aux)
+        (__do_global_dtors, __CTOR_LIST__, __DTOR_LIST__)
+        [__GNUC__ && !ORDINARY_LINK]: Remove.
+        * mem-limits.h, pre-crt0.c: Remove.
+        * unexaix.c, unexcoff.c: Don't include mem-limits.h.
+        * unexcoff.c (etext): New decl.
+        (make_hdr): Use DATA_START instead of start_of_data.
+        * vm-limit.c: Move most of mem-limits.h's contents here.
+        (data_start): New decl.  It's OK if this is approximate,
+        so simplify-away some unnecessary exactness.
+        (POINTER): Remove; all uses removed.
+        (data_space_start): Now char *, to avoid casts.
+        (exceeds_lisp_ptr): New function, replacing the old
+        EXCEEDS_LISP_PTR macro.  All uses changed.
+        (check_memory_limits): Simplify and remove casts.
+        (start_of_data) [!CANNOT_DUMP || !SYSTEM_MALLOC]: Remove.
+        (memory_warnings): Use data_start instead of start_of_data.
+
 2013-02-24  Andreas Schwab  <schwab@linux-m68k.org>
 
         * xdisp.c (set_message): Only check for debug-on-message if STRING
diff --git a/src/Makefile.in b/src/Makefile.in
index 6ee03177861..b2034a3379d 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -36,7 +36,6 @@ WINDRES = @WINDRES@
 CFLAGS = @CFLAGS@
 CPPFLAGS = @CPPFLAGS@
 LDFLAGS = @LDFLAGS@
-LD_FIRSTFLAG=@LD_FIRSTFLAG@
 EXEEXT = @EXEEXT@
 version = @version@
 # Substitute an assignment for the MAKE variable, because
@@ -102,10 +101,8 @@ LD_SWITCH_X_SITE_RPATH=@LD_SWITCH_X_SITE_RPATH@
 ## System-specific LDFLAGS.
 LD_SWITCH_SYSTEM=@LD_SWITCH_SYSTEM@
 
-## This holds any special options for linking temacs only (ie, not
-## used by configure).  Not used elsewhere because it sometimes
-## contains options that have to do with using Emacs's crt0,
-## which are only good with temacs.
+## This holds any special options for linking temacs only (i.e., not
+## used by configure).
 LD_SWITCH_SYSTEM_TEMACS=@LD_SWITCH_SYSTEM_TEMACS@
 
 ## Flags to pass to ld only for temacs.
@@ -120,14 +117,6 @@ PAXCTL = @PAXCTL@
 ## Some systems define this to request special libraries.
 LIBS_SYSTEM=@LIBS_SYSTEM@
 
-## Where to find libgcc.a, if using gcc and necessary.
-LIB_GCC=@LIB_GCC@
-
-CRT_DIR=@CRT_DIR@
-## May use $CRT_DIR.
-LIB_STANDARD=@LIB_STANDARD@
-START_FILES = @START_FILES@
-
 ## -lm, or empty.
 LIB_MATH=@LIB_MATH@
 
@@ -389,17 +378,16 @@ POST_ALLOC_OBJ=@POST_ALLOC_OBJ@
 
 ## List of object files that make-docfile should not be told about.
 otherobj= $(TERMCAP_OBJ) $(PRE_ALLOC_OBJ) $(GMALLOC_OBJ) $(RALLOC_OBJ) \
-  $(POST_ALLOC_OBJ) $(VMLIMIT_OBJ) $(WIDGET_OBJ) $(LIBOBJS)
+  $(POST_ALLOC_OBJ) $(WIDGET_OBJ) $(LIBOBJS)
 
+## All object files linked into temacs.  $(VMLIMIT_OBJ) should be first.
+ALLOBJS = $(VMLIMIT_OBJ) $(obj) $(otherobj)
 
 ## Configure inserts the file lisp.mk at this point, defining $lisp.
 @lisp_frag@
 
 
 ## Construct full set of libraries to be linked.
-## Note that SunOS needs -lm to come before -lc; otherwise, you get
-## duplicated symbols.  If the standard libraries were compiled
-## with GCC, we might need LIB_GCC again after them.
 LIBES = $(LIBS) $(W32_LIBS) $(LIBS_GNUSTEP) $(LIBX_BASE) $(LIBIMAGE) \
    $(LIBX_OTHER) $(LIBSOUND) \
    $(RSVG_LIBS) $(IMAGEMAGICK_LIBS) $(LIB_CLOCK_GETTIME) \
@@ -409,7 +397,7 @@ LIBES = $(LIBS) $(W32_LIBS) $(LIBS_GNUSTEP) $(LIBX_BASE) $(LIBIMAGE) \
    $(LIBS_TERMCAP) $(GETLOADAVG_LIBS) $(SETTINGS_LIBS) $(LIBSELINUX_LIBS) \
    $(FREETYPE_LIBS) $(FONTCONFIG_LIBS) $(LIBOTF_LIBS) $(M17N_FLT_LIBS) \
    $(LIBACL_LIBS) $(LIBGNUTLS_LIBS) $(LIB_PTHREAD) $(LIB_PTHREAD_SIGMASK) \
-   $(LIB_GCC) $(LIB_MATH) $(LIB_STANDARD) $(LIB_GCC)
+   $(LIB_MATH)
 
 all: emacs$(EXEEXT) $(OTHER_FILES)
 .PHONY: all
@@ -456,7 +444,7 @@ $(libsrc)/make-docfile$(EXEEXT):
         cd $(libsrc); $(MAKE) $(MFLAGS) make-docfile$(EXEEXT)
 
 buildobj.h: Makefile
-        echo "#define BUILDOBJ \"$(obj) $(otherobj) " "\"" > buildobj.h
+        echo "#define BUILDOBJ \"$(ALLOBJS) " "\"" >$@
 
 globals.h: gl-stamp; @true
 
@@ -468,15 +456,15 @@ gl-stamp: $(libsrc)/make-docfile$(EXEEXT) $(GLOBAL_SOURCES)
         $(srcdir)/../build-aux/move-if-change gl-tmp globals.h
         echo timestamp > $@
 
-$(obj) $(otherobj): globals.h
+$(ALLOBJS): globals.h
 
 $(lib)/libgnu.a: $(config_h)
         cd $(lib) && $(MAKE) libgnu.a
 
-temacs$(EXEEXT): $(START_FILES) stamp-oldxmenu $(obj) $(otherobj) \
+temacs$(EXEEXT): stamp-oldxmenu $(ALLOBJS) \
                  $(lib)/libgnu.a $(W32_RES)
-        $(CC) $(LD_FIRSTFLAG) $(ALL_CFLAGS) $(TEMACS_LDFLAGS) $(LDFLAGS) \
-          -o temacs $(START_FILES) $(obj) $(otherobj) $(lib)/libgnu.a $(LIBES) \
+        $(CC) $(ALL_CFLAGS) $(TEMACS_LDFLAGS) $(LDFLAGS) \
+          -o temacs $(ALLOBJS) $(lib)/libgnu.a $(LIBES) \
           $(W32_RES_LINK)
         test "$(CANNOT_DUMP)" = "yes" || \
           test "X$(PAXCTL)" = X || $(PAXCTL) -r temacs$(EXEEXT)
diff --git a/src/autodeps.mk b/src/autodeps.mk
index fb0e21366c7..8b014a7508c 100644
--- a/src/autodeps.mk
+++ b/src/autodeps.mk
@@ -2,5 +2,4 @@
 
 ## This is inserted in src/Makefile if AUTO_DEPEND=yes.
 
-ALLOBJS=$(START_FILES) ${obj} ${otherobj}
 -include $(ALLOBJS:%.o=${DEPDIR}/%.d)
diff --git a/src/deps.mk b/src/deps.mk
index 47185c9262c..83444474c59 100644
--- a/src/deps.mk
+++ b/src/deps.mk
@@ -144,7 +144,7 @@ macros.o: macros.c window.h buffer.h commands.h macros.h keyboard.h msdos.h \
    dispextern.h lisp.h globals.h $(config_h) systime.h coding.h composite.h
 gmalloc.o: gmalloc.c $(config_h)
 ralloc.o: ralloc.c lisp.h $(config_h)
-vm-limit.o: vm-limit.c mem-limits.h lisp.h globals.h $(config_h)
+vm-limit.o: vm-limit.c lisp.h globals.h $(config_h)
 marker.o: marker.c buffer.h character.h lisp.h globals.h $(config_h)
 minibuf.o: minibuf.c syntax.h frame.h window.h keyboard.h systime.h \
    buffer.h commands.h character.h msdos.h $(INTERVALS_H) keymap.h \
diff --git a/src/emacs.c b/src/emacs.c
index c494dff8cac..b96076b1340 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -521,32 +521,6 @@ DEFUN ("invocation-directory", Finvocation_directory, Sinvocation_directory,
 static char const dump_tz[] = "UtC0";
 #endif
 
-#ifndef ORDINARY_LINK
-/* We don't include crtbegin.o and crtend.o in the link,
-   so these functions and variables might be missed.
-   Provide dummy definitions to avoid error.
-   (We don't have any real constructors or destructors.)  */
-#ifdef __GNUC__
-
-/* Define a dummy function F.  Declare F too, to pacify gcc
-   -Wmissing-prototypes.  */
-#define DEFINE_DUMMY_FUNCTION(f) \
-  void f (void) ATTRIBUTE_CONST EXTERNALLY_VISIBLE; void f (void) {}
-
-#ifndef GCC_CTORS_IN_LIBC
-DEFINE_DUMMY_FUNCTION (__do_global_ctors)
-DEFINE_DUMMY_FUNCTION (__do_global_ctors_aux)
-DEFINE_DUMMY_FUNCTION (__do_global_dtors)
-/* GNU/Linux has a bug in its library; avoid an error.  */
-#ifndef GNU_LINUX
-char * __CTOR_LIST__[2] EXTERNALLY_VISIBLE = { (char *) (-1), 0 };
-#endif
-char * __DTOR_LIST__[2] EXTERNALLY_VISIBLE = { (char *) (-1), 0 };
-#endif /* GCC_CTORS_IN_LIBC */
-DEFINE_DUMMY_FUNCTION (__main)
-#endif /* __GNUC__ */
-#endif /* ORDINARY_LINK */
-
 /* Test whether the next argument in ARGV matches SSTR or a prefix of
    LSTR (at least MINLEN characters).  If so, then if VALPTR is non-null
    (the argument is supposed to have a value) store in *VALPTR either
diff --git a/src/makefile.w32-in b/src/makefile.w32-in
index 6e1873f8e49..d60331198db 100644
--- a/src/makefile.w32-in
+++ b/src/makefile.w32-in
@@ -1492,7 +1492,6 @@ $(BLD)/unexw32.$(O) : \
 
 $(BLD)/vm-limit.$(O) : \
         $(SRC)/vm-limit.c \
-        $(SRC)/mem-limits.h \
         $(SRC)/w32heap.h \
         $(NT_INC)/unistd.h \
         $(CONFIG_H) \
diff --git a/src/mem-limits.h b/src/mem-limits.h
deleted file mode 100644
index 941ccf5f121..00000000000
--- a/src/mem-limits.h
+++ /dev/null
@@ -1,43 +0,0 @@
-/* Includes for memory limit warnings.
-   Copyright (C) 1990, 1993-1996, 2001-2013 Free Software Foundation,
-   Inc.
-
-This file is part of GNU Emacs.
-
-GNU Emacs is free software: you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation, either version 3 of the License, or
-(at your option) any later version.
-
-GNU Emacs is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
-
-#ifdef MSDOS
-#include <dpmi.h>
-extern int etext;
-#endif
-
-/* Some systems need this before <sys/resource.h>.  */
-#include <sys/types.h>
-
-#ifdef HAVE_SYS_RESOURCE_H
-# include <sys/time.h>
-# include <sys/resource.h>
-#else
-# if HAVE_SYS_VLIMIT_H
-#  include <sys/vlimit.h>       /* Obsolete, says glibc */
-# endif
-#endif
-
-extern char *start_of_data (void) ATTRIBUTE_CONST;
-#if USE_LSB_TAG || UINTPTR_MAX <= VAL_MAX
-#define EXCEEDS_LISP_PTR(ptr) 0
-#else
-#define EXCEEDS_LISP_PTR(ptr) \
-  (((uintptr_t) (ptr) & ~DATA_SEG_BITS) >> VALBITS)
-#endif
diff --git a/src/pre-crt0.c b/src/pre-crt0.c
deleted file mode 100644
index 6b9618c8dc3..00000000000
--- a/src/pre-crt0.c
+++ /dev/null
@@ -1,10 +0,0 @@
-/* This file is loaded before crt0.o on machines where we do not
-   remap part of the data space into text space in unexec.
-   On these machines, there is no problem with standard crt0.o's
-   that make environ an initialized variable.  However, we do
-   need to make sure the label data_start exists anyway.  */
-
-/* Create a label to appear at the beginning of data space.
-   Its value is nonzero so that it cannot be put into bss.  */
-
-int data_start = 1;
diff --git a/src/unexaix.c b/src/unexaix.c
index da44480fdca..44a824b8c12 100644
--- a/src/unexaix.c
+++ b/src/unexaix.c
@@ -59,8 +59,6 @@ what you give them.   Help stamp out software-hoarding!  */
 #include <unistd.h>
 #include <fcntl.h>
 
-#include "mem-limits.h"
-
 extern char _data[];
 extern char _text[];
 
diff --git a/src/unexcoff.c b/src/unexcoff.c
index 466a5c0e491..2e662a34145 100644
--- a/src/unexcoff.c
+++ b/src/unexcoff.c
@@ -99,7 +99,7 @@ struct aouthdr
 
 #include <sys/file.h>
 
-#include "mem-limits.h"
+extern int etext;
 
 static long block_copy_start;           /* Old executable start point */
 static struct filehdr f_hdr;            /* File header */
@@ -168,7 +168,7 @@ make_hdr (int new, int a_out,
   pagemask = getpagesize () - 1;
 
   /* Adjust text/data boundary. */
-  data_start = (int) start_of_data ();
+  data_start = (int) DATA_START;
   data_start = ADDR_CORRECT (data_start);
   data_start = data_start & ~pagemask; /* (Down) to page boundary. */
 
diff --git a/src/vm-limit.c b/src/vm-limit.c
index fc7a253325a..3fca8bd26c1 100644
--- a/src/vm-limit.c
+++ b/src/vm-limit.c
@@ -19,7 +19,37 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <config.h>
 #include <unistd.h> /* for 'environ', on AIX */
 #include "lisp.h"
-#include "mem-limits.h"
+
+#ifdef MSDOS
+#include <dpmi.h>
+extern int etext;
+#endif
+
+/* Some systems need this before <sys/resource.h>.  */
+#include <sys/types.h>
+
+#ifdef HAVE_SYS_RESOURCE_H
+# include <sys/time.h>
+# include <sys/resource.h>
+#else
+# if HAVE_SYS_VLIMIT_H
+#  include <sys/vlimit.h>       /* Obsolete, says glibc */
+# endif
+#endif
+
+/* Start of data.  It is OK if this is approximate; it's used only as
+   a heuristic.  */
+#ifdef DATA_START
+# define data_start ((char *) DATA_START)
+#else
+extern char data_start[];
+# ifndef HAVE_DATA_START
+/* Initialize to nonzero, so that it's put into data and not bss.
+   Link this file's object code first, so that this symbol is near the
+   start of data.  */
+char data_start[1] = { 1 };
+# endif
+#endif
 
 /*
   Level number of warnings already issued.
@@ -35,12 +65,20 @@ static enum warnlevel warnlevel;
    0 means don't issue them.  */
 static void (*warn_function) (const char *);
 
-/* Start of data space; can be changed by calling malloc_init.  */
-static void *data_space_start;
+/* Start of data space; can be changed by calling memory_warnings.  */
+static char *data_space_start;
 
 /* Number of bytes of writable memory we can expect to be able to get.  */
 static size_t lim_data;
 
+/* Return true if PTR cannot be represented as an Emacs Lisp object.  */
+static bool
+exceeds_lisp_ptr (void *ptr)
+{
+  return (! USE_LSB_TAG
+          && VAL_MAX < UINTPTR_MAX
+          && ((uintptr_t) ptr & ~DATA_SEG_BITS) >> VALBITS != 0);
+}
 
 #ifdef HAVE_GETRLIMIT
 
@@ -122,10 +160,12 @@ check_memory_limits (void)
 {
 #ifdef REL_ALLOC
   extern void *(*real_morecore) (ptrdiff_t);
+#else
+  void *(*real_morecore) (ptrdiff_t) = 0;
 #endif
   extern void *(*__morecore) (ptrdiff_t);
 
-  void *cp;
+  char *cp;
   size_t five_percent;
   size_t data_size;
   enum warnlevel new_warnlevel;
@@ -135,13 +175,8 @@ check_memory_limits (void)
   five_percent = lim_data / 20;
 
   /* Find current end of memory and issue warning if getting near max */
-#ifdef REL_ALLOC
-  if (real_morecore)
-    cp = (char *) (*real_morecore) (0);
-  else
-#endif
-  cp = (char *) (*__morecore) (0);
-  data_size = (char *) cp - (char *) data_space_start;
+  cp = (real_morecore ? real_morecore : __morecore) (0);
+  data_size = cp - data_space_start;
 
   if (!warn_function)
     return;
@@ -188,49 +223,10 @@ check_memory_limits (void)
         warnlevel = warned_85;
     }
 
-  if (EXCEEDS_LISP_PTR (cp))
+  if (exceeds_lisp_ptr (cp))
     (*warn_function) ("Warning: memory in use exceeds lisp pointer size");
 }
 
-#if !defined (CANNOT_DUMP) || !defined (SYSTEM_MALLOC)
-/* Some systems that cannot dump also cannot implement these.  */
-
-/*
- *      Return the address of the start of the data segment prior to
- *      doing an unexec.  After unexec the return value is undefined.
- *      See crt0.c for further information and definition of data_start.
- *
- *      Apparently, on BSD systems this is etext at startup.  On
- *      USG systems (swapping) this is highly mmu dependent and
- *      is also dependent on whether or not the program is running
- *      with shared text.  Generally there is a (possibly large)
- *      gap between end of text and start of data with shared text.
- *
- */
-
-char *
-start_of_data (void)
-{
-#ifdef BSD_SYSTEM
-  extern char etext;
-  return (void *) &etext;
-#elif defined DATA_START
-  return (void *) DATA_START;
-#elif defined ORDINARY_LINK
-  /*
-   * This is a hack.  Since we're not linking crt0.c or pre_crt0.c,
-   * data_start isn't defined.  We take the address of environ, which
-   * is known to live at or near the start of the system crt0.c, and
-   * we don't sweat the handful of bytes that might lose.
-   */
-  return (void *) &environ;
-#else
-  extern int data_start;
-  return (void *) &data_start;
-#endif
-}
-#endif /* (not CANNOT_DUMP or not SYSTEM_MALLOC) */
-
 /* Enable memory usage warnings.
    START says where the end of pure storage is.
    WARNFUN specifies the function to call to issue a warning.  */
@@ -240,10 +236,7 @@ memory_warnings (void *start, void (*warnfun) (const char *))
 {
   extern void (* __after_morecore_hook) (void);     /* From gmalloc.c */
 
-  if (start)
-    data_space_start = start;
-  else
-    data_space_start = start_of_data ();
+  data_space_start = start ? start : data_start;
 
   warn_function = warnfun;
   __after_morecore_hook = check_memory_limits;