libgcc/crtstuff.c

   1 /* Specialized bits of code needed to support construction and
   2    destruction of file-scope objects in C++ code.
   3    Copyright (C) 1991-2020 Free Software Foundation, Inc.
   4    Contributed by Ron Guilmette (rfg@monkeys.com).
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 Under Section 7 of GPL version 3, you are granted additional
  19 permissions described in the GCC Runtime Library Exception, version
  20 3.1, as published by the Free Software Foundation.
  21
  22 You should have received a copy of the GNU General Public License and
  23 a copy of the GCC Runtime Library Exception along with this program;
  24 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 <http://www.gnu.org/licenses/>.  */
  26
  27 /* This file is a bit like libgcc2.c in that it is compiled
  28    multiple times and yields multiple .o files.
  29
  30    This file is useful on target machines where the object file format
  31    supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE).  On
  32    such systems, this file allows us to avoid running collect (or any
  33    other such slow and painful kludge).  Additionally, if the target
  34    system supports a .init section, this file allows us to support the
  35    linking of C++ code with a non-C++ main program.
  36
  37    Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then
  38    this file *will* make use of the .init section.  If that symbol is
  39    not defined however, then the .init section will not be used.
  40
  41    Currently, only ELF and COFF are supported.  It is likely however that
  42    ROSE could also be supported, if someone was willing to do the work to
  43    make whatever (small?) adaptations are needed.  (Some work may be
  44    needed on the ROSE assembler and linker also.)
  45
  46    This file must be compiled with gcc.  */
  47
  48 /* Target machine header files require this define. */
  49 #define IN_LIBGCC2
  50
  51 /* FIXME: Including auto-host is incorrect, but until we have
  52    identified the set of defines that need to go into auto-target.h,
  53    this will have to do.  */
  54 #include "auto-host.h"
  55 #undef caddr_t
  56 #undef pid_t
  57 #undef rlim_t
  58 #undef ssize_t
  59 #undef vfork
  60 #include "tconfig.h"
  61 #include "tsystem.h"
  62 #include "coretypes.h"
  63 #include "tm.h"
  64 #include "libgcc_tm.h"
  65 #include "unwind-dw2-fde.h"
  66
  67 #ifndef FORCE_CODE_SECTION_ALIGN
  68 # define FORCE_CODE_SECTION_ALIGN
  69 #endif
  70
  71 #ifndef CRT_CALL_STATIC_FUNCTION
  72 # define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC)     \
  73 static void __attribute__((__used__))                   \
  74 call_ ## FUNC (void)                                    \
  75 {                                                       \
  76   asm (SECTION_OP);                                     \
  77   FUNC ();                                              \
  78   FORCE_CODE_SECTION_ALIGN                              \
  79   asm (__LIBGCC_TEXT_SECTION_ASM_OP__);                         \
  80 }
  81 #endif
  82
  83 #if defined(TARGET_DL_ITERATE_PHDR) && \
  84    (defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__))
  85 #define BSD_DL_ITERATE_PHDR_AVAILABLE
  86 #endif
  87
  88 #if defined(OBJECT_FORMAT_ELF) \
  89     && !defined(OBJECT_FORMAT_FLAT) \
  90     && defined(HAVE_LD_EH_FRAME_HDR) \
  91     && !defined(inhibit_libc) && !defined(CRTSTUFFT_O) \
  92     && defined(BSD_DL_ITERATE_PHDR_AVAILABLE)
  93 #include <link.h>
  94 # define USE_PT_GNU_EH_FRAME
  95 #endif
  96
  97 #if defined(OBJECT_FORMAT_ELF) \
  98     && !defined(OBJECT_FORMAT_FLAT) \
  99     && defined(HAVE_LD_EH_FRAME_HDR) && defined(TARGET_DL_ITERATE_PHDR) \
 100     && !defined(inhibit_libc) && !defined(CRTSTUFFT_O) \
 101     && defined(__sun__) && defined(__svr4__)
 102 #include <link.h>
 103 # define USE_PT_GNU_EH_FRAME
 104 #endif
 105
 106 #if defined(OBJECT_FORMAT_ELF) \
 107     && !defined(OBJECT_FORMAT_FLAT) \
 108     && defined(HAVE_LD_EH_FRAME_HDR) \
 109     && !defined(inhibit_libc) && !defined(CRTSTUFFT_O) \
 110     && defined(__GLIBC__) && __GLIBC__ >= 2
 111 #include <link.h>
 112 /* uClibc pretends to be glibc 2.2 and DT_CONFIG is defined in its link.h.
 113    But it doesn't use PT_GNU_EH_FRAME ELF segment currently.  */
 114 # if !defined(__UCLIBC__) \
 115      && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \
 116      || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG)))
 117 #  define USE_PT_GNU_EH_FRAME
 118 # endif
 119 #endif
 120
 121 #if defined(OBJECT_FORMAT_ELF) \
 122     && !defined(OBJECT_FORMAT_FLAT) \
 123     && defined(HAVE_LD_EH_FRAME_HDR) \
 124     && !defined(CRTSTUFFT_O) \
 125     && defined(inhibit_libc) \
 126     && (defined(__GLIBC__) || defined(__gnu_linux__) || defined(__GNU__))
 127 /* On systems using glibc, an inhibit_libc build of libgcc is only
 128    part of a bootstrap process.  Build the same crt*.o as would be
 129    built with headers present, so that it is not necessary to build
 130    glibc more than once for the bootstrap to converge.  */
 131 # define USE_PT_GNU_EH_FRAME
 132 #endif
 133
 134 #ifdef USE_EH_FRAME_REGISTRY_ALWAYS
 135 # ifndef __LIBGCC_EH_FRAME_SECTION_NAME__
 136 #  error "Can't use explicit exception-frame-registration without __LIBGCC_EH_FRAME_SECTION_NAME__"
 137 # endif
 138 #endif
 139 #if defined(__LIBGCC_EH_FRAME_SECTION_NAME__) && (!defined(USE_PT_GNU_EH_FRAME) || defined(USE_EH_FRAME_REGISTRY_ALWAYS))
 140 # define USE_EH_FRAME_REGISTRY
 141 #endif
 142 #if defined(__LIBGCC_EH_FRAME_SECTION_NAME__) \
 143     && __LIBGCC_EH_TABLES_CAN_BE_READ_ONLY__
 144 # define EH_FRAME_SECTION_CONST const
 145 #else
 146 # define EH_FRAME_SECTION_CONST
 147 #endif
 148
 149 #if !defined(DTOR_LIST_END) && defined(OBJECT_FORMAT_ELF) \
 150     && defined(HAVE_GAS_HIDDEN) && !defined(FINI_ARRAY_SECTION_ASM_OP)
 151 # define HIDDEN_DTOR_LIST_END
 152 #endif
 153
 154 #if !defined(USE_TM_CLONE_REGISTRY) && defined(OBJECT_FORMAT_ELF)
 155 # define USE_TM_CLONE_REGISTRY 1
 156 #elif !defined(USE_TM_CLONE_REGISTRY)
 157 # define USE_TM_CLONE_REGISTRY 0
 158 #endif
 159
 160 /* We do not want to add the weak attribute to the declarations of these
 161    routines in unwind-dw2-fde.h because that will cause the definition of
 162    these symbols to be weak as well.
 163
 164    This exposes a core issue, how to handle creating weak references vs
 165    how to create weak definitions.  Either we have to have the definition
 166    of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or
 167    have a second declaration if we want a function's references to be weak,
 168    but not its definition.
 169
 170    Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until
 171    one thinks about scaling to larger problems -- i.e., the condition under
 172    which TARGET_WEAK_ATTRIBUTE is active will eventually get far too
 173    complicated.
 174
 175    So, we take an approach similar to #pragma weak -- we have a second
 176    declaration for functions that we want to have weak references.
 177
 178    Neither way is particularly good.  */
 179
 180 /* References to __register_frame_info and __deregister_frame_info should
 181    be weak in this file if at all possible.  */
 182 extern void __register_frame_info (const void *, struct object *)
 183                                   TARGET_ATTRIBUTE_WEAK;
 184 extern void __register_frame_info_bases (const void *, struct object *,
 185                                          void *, void *)
 186                                   TARGET_ATTRIBUTE_WEAK;
 187 extern void *__deregister_frame_info (const void *)
 188                                      TARGET_ATTRIBUTE_WEAK;
 189 extern void *__deregister_frame_info_bases (const void *)
 190                                      TARGET_ATTRIBUTE_WEAK;
 191 extern void __do_global_ctors_1 (void);
 192
 193 /* Likewise for transactional memory clone tables.  */
 194 extern void _ITM_registerTMCloneTable (void *, size_t) TARGET_ATTRIBUTE_WEAK;
 195 extern void _ITM_deregisterTMCloneTable (void *) TARGET_ATTRIBUTE_WEAK;
 196
 197 #ifdef OBJECT_FORMAT_ELF
 198
 199 /*  Declare a pointer to void function type.  */
 200 typedef void (*func_ptr) (void);
 201 #define STATIC static
 202
 203 #else  /* OBJECT_FORMAT_ELF */
 204
 205 #include "gbl-ctors.h"
 206
 207 #define STATIC
 208
 209 #endif /* OBJECT_FORMAT_ELF */
 210
 211 #ifdef CRT_BEGIN
 212
 213 /* NOTE:  In order to be able to support SVR4 shared libraries, we arrange
 214    to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__,
 215    __DTOR_END__ } per root executable and also one set of these symbols
 216    per shared library.  So in any given whole process image, we may have
 217    multiple definitions of each of these symbols.  In order to prevent
 218    these definitions from conflicting with one another, and in order to
 219    ensure that the proper lists are used for the initialization/finalization
 220    of each individual shared library (respectively), we give these symbols
 221    only internal (i.e. `static') linkage, and we also make it a point to
 222    refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
 223    symbol in crtbegin.o, where they are defined.  */
 224
 225 /* No need for .ctors/.dtors section if linker can place them in
 226    .init_array/.fini_array section.  */
 227 #ifndef USE_INITFINI_ARRAY
 228 /* The -1 is a flag to __do_global_[cd]tors indicating that this table
 229    does not start with a count of elements.  */
 230 #ifdef CTOR_LIST_BEGIN
 231 CTOR_LIST_BEGIN;
 232 #elif defined(__LIBGCC_CTORS_SECTION_ASM_OP__)
 233 /* Hack: force cc1 to switch to .data section early, so that assembling
 234    __CTOR_LIST__ does not undo our behind-the-back change to .ctors.  */
 235 static func_ptr force_to_data[1] __attribute__ ((__used__)) = { };
 236 asm (__LIBGCC_CTORS_SECTION_ASM_OP__);
 237 STATIC func_ptr __CTOR_LIST__[1]
 238   __attribute__ ((__used__, aligned(__alignof__(func_ptr))))
 239   = { (func_ptr) (-1) };
 240 #else
 241 STATIC func_ptr __CTOR_LIST__[1]
 242   __attribute__ ((__used__, section(".ctors"), aligned(__alignof__(func_ptr))))
 243   = { (func_ptr) (-1) };
 244 #endif /* __CTOR_LIST__ alternatives */
 245
 246 #ifdef DTOR_LIST_BEGIN
 247 DTOR_LIST_BEGIN;
 248 #elif defined(__LIBGCC_DTORS_SECTION_ASM_OP__)
 249 asm (__LIBGCC_DTORS_SECTION_ASM_OP__);
 250 STATIC func_ptr __DTOR_LIST__[1]
 251   __attribute__ ((aligned(__alignof__(func_ptr))))
 252   = { (func_ptr) (-1) };
 253 #else
 254 STATIC func_ptr __DTOR_LIST__[1]
 255   __attribute__((section(".dtors"), aligned(__alignof__(func_ptr))))
 256   = { (func_ptr) (-1) };
 257 #endif /* __DTOR_LIST__ alternatives */
 258 #endif /* USE_INITFINI_ARRAY */
 259
 260 #ifdef USE_EH_FRAME_REGISTRY
 261 /* Stick a label at the beginning of the frame unwind info so we can register
 262    and deregister it with the exception handling library code.  */
 263 STATIC EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
 264      __attribute__((section(__LIBGCC_EH_FRAME_SECTION_NAME__), aligned(4)))
 265      = { };
 266 #endif /* USE_EH_FRAME_REGISTRY */
 267
 268 #if USE_TM_CLONE_REGISTRY
 269 STATIC func_ptr __TMC_LIST__[]
 270   __attribute__((used, section(".tm_clone_table"), aligned(__alignof__(void*))))
 271   = { };
 272 # ifdef HAVE_GAS_HIDDEN
 273 extern func_ptr __TMC_END__[] __attribute__((__visibility__ ("hidden")));
 274 # endif
 275
 276 static inline void
 277 deregister_tm_clones (void)
 278 {
 279   void (*fn) (void *);
 280
 281 #ifdef HAVE_GAS_HIDDEN
 282   func_ptr *end = __TMC_END__;
 283   // Do not optimize the comparison to false.
 284   __asm ("" : "+g" (end));
 285   if (__TMC_LIST__ == end)
 286     return;
 287 #else
 288   if (__TMC_LIST__[0] == NULL)
 289     return;
 290 #endif
 291
 292   fn = _ITM_deregisterTMCloneTable;
 293   __asm ("" : "+r" (fn));
 294   if (fn)
 295     fn (__TMC_LIST__);
 296 }
 297
 298 static inline void
 299 register_tm_clones (void)
 300 {
 301   void (*fn) (void *, size_t);
 302   size_t size;
 303
 304 #ifdef HAVE_GAS_HIDDEN
 305   func_ptr *end = __TMC_END__;
 306   // Do not optimize the comparison to false.
 307   __asm ("" : "+g" (end));
 308   size = (end - __TMC_LIST__) / 2;
 309 #else
 310   for (size = 0; __TMC_LIST__[size * 2] != NULL; size++)
 311     continue;
 312 #endif
 313   if (size == 0)
 314     return;
 315
 316   fn = _ITM_registerTMCloneTable;
 317   __asm ("" : "+r" (fn));
 318   if (fn)
 319     fn (__TMC_LIST__, size);
 320 }
 321 #endif /* USE_TM_CLONE_REGISTRY */
 322
 323 #if defined(__LIBGCC_INIT_SECTION_ASM_OP__) \
 324     || defined(__LIBGCC_INIT_ARRAY_SECTION_ASM_OP__)
 325
 326 #ifdef OBJECT_FORMAT_ELF
 327
 328 #if DEFAULT_USE_CXA_ATEXIT
 329 /* Declare the __dso_handle variable.  It should have a unique value
 330    in every shared-object; in a main program its value is zero.  The
 331    object should in any case be protected.  This means the instance
 332    in one DSO or the main program is not used in another object.  The
 333    dynamic linker takes care of this.
 334    If __cxa_atexit is not being used, __dso_handle will not be used and
 335    doesn't need to be defined.  */
 336
 337 #ifdef TARGET_LIBGCC_SDATA_SECTION
 338 extern void *__dso_handle __attribute__ ((__section__ (TARGET_LIBGCC_SDATA_SECTION)));
 339 #endif
 340 #ifdef HAVE_GAS_HIDDEN
 341 extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
 342 #endif
 343 #ifdef CRTSTUFFS_O
 344 void *__dso_handle = &__dso_handle;
 345 #else
 346 void *__dso_handle = 0;
 347 #endif
 348 #endif /* DEFAULT_USE_CXA_ATEXIT */
 349
 350 /* The __cxa_finalize function may not be available so we use only a
 351    weak declaration.  */
 352 extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK;
 353
 354 /* Run all the global destructors on exit from the program.  */
 355
 356 /* Some systems place the number of pointers in the first word of the
 357    table.  On SVR4 however, that word is -1.  In all cases, the table is
 358    null-terminated.  On SVR4, we start from the beginning of the list and
 359    invoke each per-compilation-unit destructor routine in order
 360    until we find that null.
 361
 362    Note that this function MUST be static.  There will be one of these
 363    functions in each root executable and one in each shared library, but
 364    although they all have the same code, each one is unique in that it
 365    refers to one particular associated `__DTOR_LIST__' which belongs to the
 366    same particular root executable or shared library file.
 367
 368    On some systems, this routine is run more than once from the .fini,
 369    when exit is called recursively, so we arrange to remember where in
 370    the list we left off processing, and we resume at that point,
 371    should we be re-invoked.
 372
 373    This routine does not need to be run if none of the following clauses are
 374    true, as it will not do anything, so can be removed.  */
 375 #if defined(CRTSTUFFS_O) || !defined(FINI_ARRAY_SECTION_ASM_OP) \
 376   || USE_TM_CLONE_REGISTRY || defined(USE_EH_FRAME_REGISTRY)
 377 static void __attribute__((used))
 378 __do_global_dtors_aux (void)
 379 {
 380   static _Bool completed;
 381
 382   if (__builtin_expect (completed, 0))
 383     return;
 384
 385 #ifdef CRTSTUFFS_O
 386   if (__cxa_finalize)
 387     __cxa_finalize (__dso_handle);
 388 #endif
 389
 390 #ifdef FINI_ARRAY_SECTION_ASM_OP
 391   /* If we are using .fini_array then destructors will be run via that
 392      mechanism.  */
 393 #elif defined(HIDDEN_DTOR_LIST_END)
 394   {
 395     /* Safer version that makes sure only .dtors function pointers are
 396        called even if the static variable is maliciously changed.  */
 397     extern func_ptr __DTOR_END__[] __attribute__((visibility ("hidden")));
 398     static size_t dtor_idx;
 399     const size_t max_idx = __DTOR_END__ - __DTOR_LIST__ - 1;
 400     func_ptr *dtor_list;
 401
 402     __asm ("" : "=g" (dtor_list) : "0" (__DTOR_LIST__));
 403     while (dtor_idx < max_idx)
 404       dtor_list[++dtor_idx] ();
 405   }
 406 #else /* !defined (FINI_ARRAY_SECTION_ASM_OP) */
 407   {
 408     static func_ptr *p = __DTOR_LIST__ + 1;
 409     func_ptr f;
 410
 411     while ((f = *p))
 412       {
 413         p++;
 414         f ();
 415       }
 416   }
 417 #endif /* !defined(FINI_ARRAY_SECTION_ASM_OP) */
 418
 419 #if USE_TM_CLONE_REGISTRY
 420   deregister_tm_clones ();
 421 #endif /* USE_TM_CLONE_REGISTRY */
 422
 423 #ifdef USE_EH_FRAME_REGISTRY
 424 #ifdef CRT_GET_RFIB_DATA
 425   /* If we used the new __register_frame_info_bases interface,
 426      make sure that we deregister from the same place.  */
 427   if (__deregister_frame_info_bases)
 428     __deregister_frame_info_bases (__EH_FRAME_BEGIN__);
 429 #else
 430   if (__deregister_frame_info)
 431     __deregister_frame_info (__EH_FRAME_BEGIN__);
 432 #endif
 433 #endif
 434
 435   completed = 1;
 436 }
 437
 438 /* Stick a call to __do_global_dtors_aux into the .fini section.  */
 439 #ifdef FINI_SECTION_ASM_OP
 440 CRT_CALL_STATIC_FUNCTION (FINI_SECTION_ASM_OP, __do_global_dtors_aux)
 441 #elif defined (FINI_ARRAY_SECTION_ASM_OP)
 442 #if defined(__FDPIC__)
 443 __asm__("\t.equ\t__do_global_dtors_aux_alias, __do_global_dtors_aux\n");
 444 extern char __do_global_dtors_aux_alias;
 445 static void *__do_global_dtors_aux_fini_array_entry[]
 446 __attribute__ ((__used__, section(".fini_array"), aligned(sizeof(void *))))
 447      = { &__do_global_dtors_aux_alias };
 448 #else /* defined(__FDPIC__) */
 449 static func_ptr __do_global_dtors_aux_fini_array_entry[]
 450   __attribute__ ((__used__, section(".fini_array"),
 451                   aligned(__alignof__(func_ptr)))) = { __do_global_dtors_aux };
 452 #endif /* defined(__FDPIC__) */
 453 #else /* !FINI_SECTION_ASM_OP && !FINI_ARRAY_SECTION_ASM_OP */
 454 static void __attribute__((used))
 455 __do_global_dtors_aux_1 (void)
 456 {
 457   atexit (__do_global_dtors_aux);
 458 }
 459 CRT_CALL_STATIC_FUNCTION (__LIBGCC_INIT_SECTION_ASM_OP__,
 460                           __do_global_dtors_aux_1)
 461 #endif
 462 #endif /* defined(CRTSTUFFS_O) || !defined(FINI_ARRAY_SECTION_ASM_OP)
 463   || USE_TM_CLONE_REGISTRY || defined(USE_EH_FRAME_REGISTRY) */
 464
 465 #if defined(USE_EH_FRAME_REGISTRY) || USE_TM_CLONE_REGISTRY
 466 /* Stick a call to __register_frame_info into the .init section.  For some
 467    reason calls with no arguments work more reliably in .init, so stick the
 468    call in another function.  */
 469
 470 static void __attribute__((used))
 471 frame_dummy (void)
 472 {
 473 #ifdef USE_EH_FRAME_REGISTRY
 474   static struct object object;
 475 #ifdef CRT_GET_RFIB_DATA
 476   void *tbase, *dbase;
 477   tbase = 0;
 478   CRT_GET_RFIB_DATA (dbase);
 479   if (__register_frame_info_bases)
 480     __register_frame_info_bases (__EH_FRAME_BEGIN__, &object, tbase, dbase);
 481 #else
 482   if (__register_frame_info)
 483     __register_frame_info (__EH_FRAME_BEGIN__, &object);
 484 #endif /* CRT_GET_RFIB_DATA */
 485 #endif /* USE_EH_FRAME_REGISTRY */
 486
 487 #if USE_TM_CLONE_REGISTRY
 488   register_tm_clones ();
 489 #endif /* USE_TM_CLONE_REGISTRY */
 490 }
 491
 492 #ifdef __LIBGCC_INIT_SECTION_ASM_OP__
 493 CRT_CALL_STATIC_FUNCTION (__LIBGCC_INIT_SECTION_ASM_OP__, frame_dummy)
 494 #else /* defined(__LIBGCC_INIT_SECTION_ASM_OP__) */
 495 #if defined(__FDPIC__)
 496 __asm__("\t.equ\t__frame_dummy_alias, frame_dummy\n");
 497 extern char __frame_dummy_alias;
 498 static void *__frame_dummy_init_array_entry[]
 499 __attribute__ ((__used__, section(".init_array"), aligned(sizeof(void *))))
 500      = { &__frame_dummy_alias };
 501 #else /* defined(__FDPIC__) */
 502 static func_ptr __frame_dummy_init_array_entry[]
 503   __attribute__ ((__used__, section(".init_array"),
 504                   aligned(__alignof__(func_ptr)))) = { frame_dummy };
 505 #endif /* defined(__FDPIC__) */
 506 #endif /* !defined(__LIBGCC_INIT_SECTION_ASM_OP__) */
 507 #endif /* USE_EH_FRAME_REGISTRY || USE_TM_CLONE_REGISTRY */
 508
 509 #else  /* OBJECT_FORMAT_ELF */
 510
 511 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
 512    and once in crtend.o).  It must be declared static to avoid a link
 513    error.  Here, we define __do_global_ctors as an externally callable
 514    function.  It is externally callable so that __main can invoke it when
 515    INVOKE__main is defined.  This has the additional effect of forcing cc1
 516    to switch to the .text section.  */
 517
 518 static void __do_global_ctors_aux (void);
 519 void
 520 __do_global_ctors (void)
 521 {
 522 #ifdef INVOKE__main
 523   /* If __main won't actually call __do_global_ctors then it doesn't matter
 524      what's inside the function.  The inside of __do_global_ctors_aux is
 525      called automatically in that case.  And the Alliant fx2800 linker
 526      crashes on this reference.  So prevent the crash.  */
 527   __do_global_ctors_aux ();
 528 #endif
 529 }
 530
 531 asm (__LIBGCC_INIT_SECTION_ASM_OP__);   /* cc1 doesn't know that we are switching! */
 532
 533 /* A routine to invoke all of the global constructors upon entry to the
 534    program.  We put this into the .init section (for systems that have
 535    such a thing) so that we can properly perform the construction of
 536    file-scope static-storage C++ objects within shared libraries.  */
 537
 538 static void __attribute__((used))
 539 __do_global_ctors_aux (void)    /* prologue goes in .init section */
 540 {
 541   FORCE_CODE_SECTION_ALIGN      /* explicit align before switch to .text */
 542   asm (__LIBGCC_TEXT_SECTION_ASM_OP__); /* don't put epilogue and body in .init */
 543   DO_GLOBAL_CTORS_BODY;
 544   atexit (__do_global_dtors);
 545 }
 546
 547 #endif /* OBJECT_FORMAT_ELF */
 548
 549 #elif defined(HAS_INIT_SECTION) /* ! __LIBGCC_INIT_SECTION_ASM_OP__ */
 550
 551 extern void __do_global_dtors (void);
 552
 553 /* This case is used by the Irix 6 port, which supports named sections but
 554    not an SVR4-style .fini section.  __do_global_dtors can be non-static
 555    in this case because we protect it with -hidden_symbol.  */
 556
 557 void
 558 __do_global_dtors (void)
 559 {
 560   func_ptr *p, f;
 561   for (p = __DTOR_LIST__ + 1; (f = *p); p++)
 562     f ();
 563
 564 #if USE_TM_CLONE_REGISTRY
 565   deregister_tm_clones ();
 566 #endif /* USE_TM_CLONE_REGISTRY */
 567
 568 #ifdef USE_EH_FRAME_REGISTRY
 569   if (__deregister_frame_info)
 570     __deregister_frame_info (__EH_FRAME_BEGIN__);
 571 #endif
 572 }
 573
 574 #if defined(USE_EH_FRAME_REGISTRY) || USE_TM_CLONE_REGISTRY
 575 /* A helper function for __do_global_ctors, which is in crtend.o.  Here
 576    in crtbegin.o, we can reference a couple of symbols not visible there.
 577    Plus, since we're before libgcc.a, we have no problems referencing
 578    functions from there.  */
 579 void
 580 __do_global_ctors_1(void)
 581 {
 582 #ifdef USE_EH_FRAME_REGISTRY
 583   static struct object object;
 584   if (__register_frame_info)
 585     __register_frame_info (__EH_FRAME_BEGIN__, &object);
 586 #endif
 587
 588 #if USE_TM_CLONE_REGISTRY
 589   register_tm_clones ();
 590 #endif /* USE_TM_CLONE_REGISTRY */
 591 }
 592 #endif /* USE_EH_FRAME_REGISTRY || USE_TM_CLONE_REGISTRY */
 593
 594 #else /* ! __LIBGCC_INIT_SECTION_ASM_OP__ && ! HAS_INIT_SECTION */
 595 #error "What are you doing with crtstuff.c, then?"
 596 #endif
 597
 598 #elif defined(CRT_END) /* ! CRT_BEGIN */
 599
 600 /* No need for .ctors/.dtors section if linker can place them in
 601    .init_array/.fini_array section.  */
 602 #ifndef USE_INITFINI_ARRAY
 603 /* Put a word containing zero at the end of each of our two lists of function
 604    addresses.  Note that the words defined here go into the .ctors and .dtors
 605    sections of the crtend.o file, and since that file is always linked in
 606    last, these words naturally end up at the very ends of the two lists
 607    contained in these two sections.  */
 608
 609 #ifdef CTOR_LIST_END
 610 CTOR_LIST_END;
 611 #elif defined(__LIBGCC_CTORS_SECTION_ASM_OP__)
 612 /* Hack: force cc1 to switch to .data section early, so that assembling
 613    __CTOR_LIST__ does not undo our behind-the-back change to .ctors.  */
 614 static func_ptr force_to_data[1] __attribute__ ((__used__)) = { };
 615 asm (__LIBGCC_CTORS_SECTION_ASM_OP__);
 616 STATIC func_ptr __CTOR_END__[1]
 617   __attribute__((aligned(__alignof__(func_ptr))))
 618   = { (func_ptr) 0 };
 619 #else
 620 STATIC func_ptr __CTOR_END__[1]
 621   __attribute__((section(".ctors"), aligned(__alignof__(func_ptr))))
 622   = { (func_ptr) 0 };
 623 #endif
 624
 625 #ifdef DTOR_LIST_END
 626 DTOR_LIST_END;
 627 #elif defined(HIDDEN_DTOR_LIST_END)
 628 #ifdef __LIBGCC_DTORS_SECTION_ASM_OP__
 629 asm (__LIBGCC_DTORS_SECTION_ASM_OP__);
 630 #endif
 631 func_ptr __DTOR_END__[1]
 632   __attribute__ ((used,
 633 #ifndef __LIBGCC_DTORS_SECTION_ASM_OP__
 634                   section(".dtors"),
 635 #endif
 636                   aligned(__alignof__(func_ptr)), visibility ("hidden")))
 637   = { (func_ptr) 0 };
 638 #elif defined(__LIBGCC_DTORS_SECTION_ASM_OP__)
 639 asm (__LIBGCC_DTORS_SECTION_ASM_OP__);
 640 STATIC func_ptr __DTOR_END__[1]
 641   __attribute__ ((used, aligned(__alignof__(func_ptr))))
 642   = { (func_ptr) 0 };
 643 #else
 644 STATIC func_ptr __DTOR_END__[1]
 645   __attribute__((used, section(".dtors"), aligned(__alignof__(func_ptr))))
 646   = { (func_ptr) 0 };
 647 #endif
 648 #endif /* USE_INITFINI_ARRAY */
 649
 650 #ifdef __LIBGCC_EH_FRAME_SECTION_NAME__
 651 /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
 652    this would be the 'length' field in a real FDE.  */
 653 # if __INT_MAX__ == 2147483647
 654 typedef int int32;
 655 # elif __LONG_MAX__ == 2147483647
 656 typedef long int32;
 657 # elif __SHRT_MAX__ == 2147483647
 658 typedef short int32;
 659 # else
 660 #  error "Missing a 4 byte integer"
 661 # endif
 662 STATIC EH_FRAME_SECTION_CONST int32 __FRAME_END__[]
 663      __attribute__ ((used, section(__LIBGCC_EH_FRAME_SECTION_NAME__),
 664                      aligned(__alignof__(int32))))
 665      = { 0 };
 666 #endif /* __LIBGCC_EH_FRAME_SECTION_NAME__ */
 667
 668 #if USE_TM_CLONE_REGISTRY
 669 # ifndef HAVE_GAS_HIDDEN
 670 static
 671 # endif
 672 func_ptr __TMC_END__[]
 673   __attribute__((used, section(".tm_clone_table"),
 674                  aligned(__alignof__(void *))))
 675 # ifdef HAVE_GAS_HIDDEN
 676   __attribute__((__visibility__ ("hidden"))) = { };
 677 # else
 678   = { 0, 0 };
 679 # endif
 680 #endif /* USE_TM_CLONE_REGISTRY */
 681
 682 #ifdef __LIBGCC_INIT_ARRAY_SECTION_ASM_OP__
 683
 684 /* If we are using .init_array, there is nothing to do.  */
 685
 686 #elif defined(__LIBGCC_INIT_SECTION_ASM_OP__)
 687
 688 #ifdef OBJECT_FORMAT_ELF
 689 static void __attribute__((used))
 690 __do_global_ctors_aux (void)
 691 {
 692   func_ptr *p;
 693   for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
 694     (*p) ();
 695 }
 696
 697 /* Stick a call to __do_global_ctors_aux into the .init section.  */
 698 CRT_CALL_STATIC_FUNCTION (__LIBGCC_INIT_SECTION_ASM_OP__, __do_global_ctors_aux)
 699 #else  /* OBJECT_FORMAT_ELF */
 700
 701 /* Stick the real initialization code, followed by a normal sort of
 702    function epilogue at the very end of the .init section for this
 703    entire root executable file or for this entire shared library file.
 704
 705    Note that we use some tricks here to get *just* the body and just
 706    a function epilogue (but no function prologue) into the .init
 707    section of the crtend.o file.  Specifically, we switch to the .text
 708    section, start to define a function, and then we switch to the .init
 709    section just before the body code.
 710
 711    Earlier on, we put the corresponding function prologue into the .init
 712    section of the crtbegin.o file (which will be linked in first).
 713
 714    Note that we want to invoke all constructors for C++ file-scope static-
 715    storage objects AFTER any other possible initialization actions which
 716    may be performed by the code in the .init section contributions made by
 717    other libraries, etc.  That's because those other initializations may
 718    include setup operations for very primitive things (e.g. initializing
 719    the state of the floating-point coprocessor, etc.) which should be done
 720    before we start to execute any of the user's code.  */
 721
 722 static void
 723 __do_global_ctors_aux (void)    /* prologue goes in .text section */
 724 {
 725   asm (__LIBGCC_INIT_SECTION_ASM_OP__);
 726   DO_GLOBAL_CTORS_BODY;
 727   atexit (__do_global_dtors);
 728 }                               /* epilogue and body go in .init section */
 729
 730 FORCE_CODE_SECTION_ALIGN
 731 asm (__LIBGCC_TEXT_SECTION_ASM_OP__);
 732
 733 #endif /* OBJECT_FORMAT_ELF */
 734
 735 #elif defined(HAS_INIT_SECTION) /* ! __LIBGCC_INIT_SECTION_ASM_OP__ */
 736
 737 extern void __do_global_ctors (void);
 738
 739 /* This case is used by the Irix 6 port, which supports named sections but
 740    not an SVR4-style .init section.  __do_global_ctors can be non-static
 741    in this case because we protect it with -hidden_symbol.  */
 742 void
 743 __do_global_ctors (void)
 744 {
 745   func_ptr *p;
 746 #if defined(USE_EH_FRAME_REGISTRY) || USE_TM_CLONE_REGISTRY
 747   __do_global_ctors_1();
 748 #endif
 749   for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
 750     (*p) ();
 751 }
 752
 753 #else /* ! __LIBGCC_INIT_SECTION_ASM_OP__ && ! HAS_INIT_SECTION */
 754 #error "What are you doing with crtstuff.c, then?"
 755 #endif
 756
 757 #else /* ! CRT_BEGIN && ! CRT_END */
 758 #error "One of CRT_BEGIN or CRT_END must be defined."
 759 #endif