[COMMITTED PATCH] Add sysdeps/init_array to produce empty crt[in].o and use .preinit_array for gcrt1.o

[Roland McGrath <roland at hack dot frob dot com>]

Seeing no feedback in the weeks since I posted this, and as it does not
affect anybody else's configurations, I've put this in.


Thanks,
Roland


2013-03-12  Roland McGrath  <roland@hack.frob.com>

	* sysdeps/init_array/elf-init.c: New file.
	* csu/elf-init.c
	(__libc_csu_init) [!NO_INITFINI]: Conditionalize _init call on this.
	(__libc_csu_fini) [!NO_INITFINI]: Conditionalize _fini call on this.

	* csu/gmon-start.c [GMON_START_ARRAY_SECTION]: Don't define
	__gmon_start__ as global, but as static with a .preinit_array pointer.
	* sysdeps/init_array/gmon-start.c: New file.  Use that.
	* sysdeps/init_array/crti.S: New file, empty except for comments.
	* sysdeps/init_array/crtn.S: Likewise.

--- a/csu/elf-init.c
+++ b/csu/elf-init.c
@@ -49,10 +49,13 @@ extern void (*__fini_array_start []) (void) attribute_hidden;
 extern void (*__fini_array_end []) (void) attribute_hidden;
 
 
+#ifndef NO_INITFINI
 /* These function symbols are provided for the .init/.fini section entry
    points automagically by the linker.  */
 extern void _init (void);
 extern void _fini (void);
+#endif
+
 
 /* These functions are passed to __libc_start_main by the startup code.
    These get statically linked into each program.  For dynamically linked
@@ -76,7 +79,9 @@ __libc_csu_init (int argc, char **argv, char **envp)
   }
 #endif
 
+#ifndef NO_INITFINI
   _init ();
+#endif
 
   const size_t size = __init_array_end - __init_array_start;
   for (size_t i = 0; i < size; i++)
@@ -94,6 +99,8 @@ __libc_csu_fini (void)
   while (i-- > 0)
     (*__fini_array_start [i]) ();
 
+# ifndef NO_INITFINI
   _fini ();
+# endif
 #endif
 }
--- a/csu/gmon-start.c
+++ b/csu/gmon-start.c
@@ -59,10 +59,17 @@ extern char etext[];
 # endif
 #endif
 
+#ifdef GMON_START_ARRAY_SECTION
+static void __gmon_start__ (void);
+static void (*const gmon_start_initializer) (void)
+  __attribute__ ((used, section (GMON_START_ARRAY_SECTION))) = &__gmon_start__;
+static
+#else
 /* We cannot use the normal constructor mechanism to call
    __gmon_start__ because gcrt1.o appears before crtbegin.o in the link.
    Instead crti.o calls it specially.  */
 extern void __gmon_start__ (void);
+#endif
 
 void
 __gmon_start__ (void)
--- /dev/null
+++ b/sysdeps/init_array/crti.S
@@ -0,0 +1,13 @@
+/* Dummy crti file.
+
+   In this configuration, crti.o and crtn.o are both empty because the
+   .init_array/.fini_array sections are used exclusively.
+
+   Older ports cannot use this because even if the linker used to
+   build libc itself has .init_array support, we don't want to produce
+   a crt[in].o that presume a linker that new will be used to link
+   other things later.
+
+   But new configurations without compatibility concerns for
+   toolchains without .init_array support can use this to avoid the
+   superfluous .init and .fini boilerplate code.  */
--- /dev/null
+++ b/sysdeps/init_array/crtn.S
@@ -0,0 +1,13 @@
+/* Dummy crtn file.
+
+   In this configuration, crti.o and crtn.o are both empty because the
+   .init_array/.fini_array sections are used exclusively.
+
+   Older ports cannot use this because even if the linker used to
+   build libc itself has .init_array support, we don't want to produce
+   a crt[in].o that presume a linker that new will be used to link
+   other things later.
+
+   But new configurations without compatibility concerns for
+   toolchains without .init_array support can use this to avoid the
+   superfluous .init and .fini boilerplate code.  */
--- /dev/null
+++ b/sysdeps/init_array/elf-init.c
@@ -0,0 +1,37 @@
+/* Startup support for ELF initializers/finalizers in the main executable.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   In addition to the permissions in the GNU Lesser General Public
+   License, the Free Software Foundation gives you unlimited
+   permission to link the compiled version of this file with other
+   programs, and to distribute those programs without any restriction
+   coming from the use of this file. (The GNU Lesser General Public
+   License restrictions do apply in other respects; for example, they
+   cover modification of the file, and distribution when not linked
+   into another program.)
+
+   Note that people who make modified versions of this file are not
+   obligated to grant this special exception for their modified
+   versions; it is their choice whether to do so. The GNU Lesser
+   General Public License gives permission to release a modified
+   version without this exception; this exception also makes it
+   possible to release a modified version which carries forward this
+   exception.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#define NO_INITFINI
+#include <csu/elf-init.c>
--- /dev/null
+++ b/sysdeps/init_array/gmon-start.c
@@ -0,0 +1,41 @@
+/* gmon startup hook using .preinit_array.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   In addition to the permissions in the GNU Lesser General Public
+   License, the Free Software Foundation gives you unlimited
+   permission to link the compiled version of this file with other
+   programs, and to distribute those programs without any restriction
+   coming from the use of this file.  (The GNU Lesser General Public
+   License restrictions do apply in other respects; for example, they
+   cover modification of the file, and distribution when not linked
+   into another program.)
+
+   Note that people who make modified versions of this file are not
+   obligated to grant this special exception for their modified
+   versions; it is their choice whether to do so.  The GNU Lesser
+   General Public License gives permission to release a modified
+   version without this exception; this exception also makes it
+   possible to release a modified version which carries forward this
+   exception.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Instead of defining __gmon_start__ globally in gcrt1.o, we make it
+   static and just put a pointer to it into the .preinit_array section.  */
+
+#define GMON_START_ARRAY_SECTION	".preinit_array"
+
+#include <csu/gmon-start.c>