1 /* Specialized bits of code needed to support construction and
2 destruction of file-scope objects in C++ code.
3 Copyright (C) 1991, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001
4 2002, 2003, 2004, 2005, 2006, 2007, 2009 Free Software Foundation, Inc.
5 Contributed by Ron Guilmette (rfg@monkeys.com).
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify it under
10 the terms of the GNU General Public License as published by the Free
11 Software Foundation; either version 2, or (at your option) any later
14 In addition to the permissions in the GNU General Public License, the
15 Free Software Foundation gives you unlimited permission to link the
16 compiled version of this file into combinations with other programs,
17 and to distribute those combinations without any restriction coming
18 from the use of this file. (The General Public License restrictions
19 do apply in other respects; for example, they cover modification of
20 the file, and distribution when not linked into a combine
23 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
24 WARRANTY; without even the implied warranty of MERCHANTABILITY or
25 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
28 You should have received a copy of the GNU General Public License
29 along with GCC; see the file COPYING. If not, write to the Free
30 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
33 /* This file is a bit like libgcc2.c in that it is compiled
34 multiple times and yields multiple .o files.
36 This file is useful on target machines where the object file format
37 supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE). On
38 such systems, this file allows us to avoid running collect (or any
39 other such slow and painful kludge). Additionally, if the target
40 system supports a .init section, this file allows us to support the
41 linking of C++ code with a non-C++ main program.
43 Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then
44 this file *will* make use of the .init section. If that symbol is
45 not defined however, then the .init section will not be used.
47 Currently, only ELF and COFF are supported. It is likely however that
48 ROSE could also be supported, if someone was willing to do the work to
49 make whatever (small?) adaptations are needed. (Some work may be
50 needed on the ROSE assembler and linker also.)
52 This file must be compiled with gcc. */
54 /* Target machine header files require this define. */
57 /* FIXME: Including auto-host is incorrect, but until we have
58 identified the set of defines that need to go into auto-target.h,
59 this will have to do. */
60 #include "auto-host.h"
67 #include "coretypes.h"
69 #include "unwind-dw2-fde.h"
71 #ifndef FORCE_CODE_SECTION_ALIGN
72 # define FORCE_CODE_SECTION_ALIGN
75 #ifndef CRT_CALL_STATIC_FUNCTION
76 # define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC) \
77 static void __attribute__((__used__)) \
78 call_ ## FUNC (void) \
82 FORCE_CODE_SECTION_ALIGN \
83 asm (TEXT_SECTION_ASM_OP); \
87 #if defined(OBJECT_FORMAT_ELF) \
88 && !defined(OBJECT_FORMAT_FLAT) \
89 && defined(HAVE_LD_EH_FRAME_HDR) \
90 && !defined(inhibit_libc) && !defined(CRTSTUFFT_O) \
91 && defined(__GLIBC__) && __GLIBC__ >= 2
93 /* uClibc pretends to be glibc 2.2 and DT_CONFIG is defined in its link.h.
94 But it doesn't use PT_GNU_EH_FRAME ELF segment currently. */
95 # if !defined(__UCLIBC__) \
96 && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \
97 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG)))
98 # define USE_PT_GNU_EH_FRAME
101 #if defined(EH_FRAME_SECTION_NAME) && !defined(USE_PT_GNU_EH_FRAME)
102 # define USE_EH_FRAME_REGISTRY
104 #if defined(EH_FRAME_SECTION_NAME) && EH_TABLES_CAN_BE_READ_ONLY
105 # define EH_FRAME_SECTION_CONST const
107 # define EH_FRAME_SECTION_CONST
110 #if !defined(DTOR_LIST_END) && defined(OBJECT_FORMAT_ELF) \
111 && defined(HAVE_GAS_HIDDEN) && !defined(FINI_ARRAY_SECTION_ASM_OP)
112 # define HIDDEN_DTOR_LIST_END
115 /* We do not want to add the weak attribute to the declarations of these
116 routines in unwind-dw2-fde.h because that will cause the definition of
117 these symbols to be weak as well.
119 This exposes a core issue, how to handle creating weak references vs
120 how to create weak definitions. Either we have to have the definition
121 of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or
122 have a second declaration if we want a function's references to be weak,
123 but not its definition.
125 Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until
126 one thinks about scaling to larger problems -- i.e., the condition under
127 which TARGET_WEAK_ATTRIBUTE is active will eventually get far too
130 So, we take an approach similar to #pragma weak -- we have a second
131 declaration for functions that we want to have weak references.
133 Neither way is particularly good. */
135 /* References to __register_frame_info and __deregister_frame_info should
136 be weak in this file if at all possible. */
137 extern void __register_frame_info (const void *, struct object *)
138 TARGET_ATTRIBUTE_WEAK;
139 extern void __register_frame_info_bases (const void *, struct object *,
141 TARGET_ATTRIBUTE_WEAK;
142 extern void *__deregister_frame_info (const void *)
143 TARGET_ATTRIBUTE_WEAK;
144 extern void *__deregister_frame_info_bases (const void *)
145 TARGET_ATTRIBUTE_WEAK;
146 extern void __do_global_ctors_1 (void);
148 /* Likewise for _Jv_RegisterClasses. */
149 extern void _Jv_RegisterClasses (void *) TARGET_ATTRIBUTE_WEAK;
151 #ifdef OBJECT_FORMAT_ELF
153 /* Declare a pointer to void function type. */
154 typedef void (*func_ptr) (void);
155 #define STATIC static
157 #else /* OBJECT_FORMAT_ELF */
159 #include "gbl-ctors.h"
163 #endif /* OBJECT_FORMAT_ELF */
167 /* NOTE: In order to be able to support SVR4 shared libraries, we arrange
168 to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__,
169 __DTOR_END__ } per root executable and also one set of these symbols
170 per shared library. So in any given whole process image, we may have
171 multiple definitions of each of these symbols. In order to prevent
172 these definitions from conflicting with one another, and in order to
173 ensure that the proper lists are used for the initialization/finalization
174 of each individual shared library (respectively), we give these symbols
175 only internal (i.e. `static') linkage, and we also make it a point to
176 refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
177 symbol in crtbegin.o, where they are defined. */
179 /* The -1 is a flag to __do_global_[cd]tors indicating that this table
180 does not start with a count of elements. */
181 #ifdef CTOR_LIST_BEGIN
183 #elif defined(CTORS_SECTION_ASM_OP)
184 /* Hack: force cc1 to switch to .data section early, so that assembling
185 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */
186 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
187 asm (CTORS_SECTION_ASM_OP);
188 STATIC func_ptr __CTOR_LIST__[1]
189 __attribute__ ((__unused__, aligned(sizeof(func_ptr))))
190 = { (func_ptr) (-1) };
192 STATIC func_ptr __CTOR_LIST__[1]
193 __attribute__ ((__unused__, section(".ctors"), aligned(sizeof(func_ptr))))
194 = { (func_ptr) (-1) };
195 #endif /* __CTOR_LIST__ alternatives */
197 #ifdef DTOR_LIST_BEGIN
199 #elif defined(DTORS_SECTION_ASM_OP)
200 asm (DTORS_SECTION_ASM_OP);
201 STATIC func_ptr __DTOR_LIST__[1]
202 __attribute__ ((aligned(sizeof(func_ptr))))
203 = { (func_ptr) (-1) };
205 STATIC func_ptr __DTOR_LIST__[1]
206 __attribute__((section(".dtors"), aligned(sizeof(func_ptr))))
207 = { (func_ptr) (-1) };
208 #endif /* __DTOR_LIST__ alternatives */
210 #ifdef USE_EH_FRAME_REGISTRY
211 /* Stick a label at the beginning of the frame unwind info so we can register
212 and deregister it with the exception handling library code. */
213 STATIC EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
214 __attribute__((section(EH_FRAME_SECTION_NAME), aligned(4)))
216 #endif /* USE_EH_FRAME_REGISTRY */
218 #ifdef JCR_SECTION_NAME
219 /* Stick a label at the beginning of the java class registration info
220 so we can register them properly. */
221 STATIC void *__JCR_LIST__[]
222 __attribute__ ((unused, section(JCR_SECTION_NAME), aligned(sizeof(void*))))
224 #endif /* JCR_SECTION_NAME */
226 #if defined(INIT_SECTION_ASM_OP) || defined(INIT_ARRAY_SECTION_ASM_OP)
228 #ifdef OBJECT_FORMAT_ELF
230 /* Declare the __dso_handle variable. It should have a unique value
231 in every shared-object; in a main program its value is zero. The
232 object should in any case be protected. This means the instance
233 in one DSO or the main program is not used in another object. The
234 dynamic linker takes care of this. */
236 #ifdef TARGET_LIBGCC_SDATA_SECTION
237 extern void *__dso_handle __attribute__ ((__section__ (TARGET_LIBGCC_SDATA_SECTION)));
239 #ifdef HAVE_GAS_HIDDEN
240 extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
243 void *__dso_handle = &__dso_handle;
245 void *__dso_handle = 0;
248 /* The __cxa_finalize function may not be available so we use only a
250 extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK;
252 /* Run all the global destructors on exit from the program. */
254 /* Some systems place the number of pointers in the first word of the
255 table. On SVR4 however, that word is -1. In all cases, the table is
256 null-terminated. On SVR4, we start from the beginning of the list and
257 invoke each per-compilation-unit destructor routine in order
258 until we find that null.
260 Note that this function MUST be static. There will be one of these
261 functions in each root executable and one in each shared library, but
262 although they all have the same code, each one is unique in that it
263 refers to one particular associated `__DTOR_LIST__' which belongs to the
264 same particular root executable or shared library file.
266 On some systems, this routine is run more than once from the .fini,
267 when exit is called recursively, so we arrange to remember where in
268 the list we left off processing, and we resume at that point,
269 should we be re-invoked. */
271 static void __attribute__((used))
272 __do_global_dtors_aux (void)
274 static _Bool completed;
276 if (__builtin_expect (completed, 0))
281 __cxa_finalize (__dso_handle);
284 #ifdef FINI_ARRAY_SECTION_ASM_OP
285 /* If we are using .fini_array then destructors will be run via that
287 #elif defined(HIDDEN_DTOR_LIST_END)
289 /* Safer version that makes sure only .dtors function pointers are
290 called even if the static variable is maliciously changed. */
291 extern func_ptr __DTOR_END__[] __attribute__((visibility ("hidden")));
292 static size_t dtor_idx;
293 const size_t max_idx = __DTOR_END__ - __DTOR_LIST__ - 1;
296 while (dtor_idx < max_idx)
298 f = __DTOR_LIST__[++dtor_idx];
302 #else /* !defined (FINI_ARRAY_SECTION_ASM_OP) */
304 static func_ptr *p = __DTOR_LIST__ + 1;
313 #endif /* !defined(FINI_ARRAY_SECTION_ASM_OP) */
315 #ifdef USE_EH_FRAME_REGISTRY
316 #ifdef CRT_GET_RFIB_DATA
317 /* If we used the new __register_frame_info_bases interface,
318 make sure that we deregister from the same place. */
319 if (__deregister_frame_info_bases)
320 __deregister_frame_info_bases (__EH_FRAME_BEGIN__);
322 if (__deregister_frame_info)
323 __deregister_frame_info (__EH_FRAME_BEGIN__);
330 /* Stick a call to __do_global_dtors_aux into the .fini section. */
331 #ifdef FINI_SECTION_ASM_OP
332 CRT_CALL_STATIC_FUNCTION (FINI_SECTION_ASM_OP, __do_global_dtors_aux)
333 #else /* !defined(FINI_SECTION_ASM_OP) */
334 static func_ptr __do_global_dtors_aux_fini_array_entry[]
335 __attribute__ ((__unused__, section(".fini_array")))
336 = { __do_global_dtors_aux };
337 #endif /* !defined(FINI_SECTION_ASM_OP) */
339 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
340 /* Stick a call to __register_frame_info into the .init section. For some
341 reason calls with no arguments work more reliably in .init, so stick the
342 call in another function. */
344 static void __attribute__((used))
347 #ifdef USE_EH_FRAME_REGISTRY
348 static struct object object;
349 #ifdef CRT_GET_RFIB_DATA
352 CRT_GET_RFIB_DATA (dbase);
353 if (__register_frame_info_bases)
354 __register_frame_info_bases (__EH_FRAME_BEGIN__, &object, tbase, dbase);
356 if (__register_frame_info)
357 __register_frame_info (__EH_FRAME_BEGIN__, &object);
358 #endif /* CRT_GET_RFIB_DATA */
359 #endif /* USE_EH_FRAME_REGISTRY */
360 #ifdef JCR_SECTION_NAME
363 void (*register_classes) (void *) = _Jv_RegisterClasses;
364 __asm ("" : "+r" (register_classes));
365 if (register_classes)
366 register_classes (__JCR_LIST__);
368 #endif /* JCR_SECTION_NAME */
371 #ifdef INIT_SECTION_ASM_OP
372 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, frame_dummy)
373 #else /* defined(INIT_SECTION_ASM_OP) */
374 static func_ptr __frame_dummy_init_array_entry[]
375 __attribute__ ((__unused__, section(".init_array")))
377 #endif /* !defined(INIT_SECTION_ASM_OP) */
378 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
380 #else /* OBJECT_FORMAT_ELF */
382 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
383 and once in crtend.o). It must be declared static to avoid a link
384 error. Here, we define __do_global_ctors as an externally callable
385 function. It is externally callable so that __main can invoke it when
386 INVOKE__main is defined. This has the additional effect of forcing cc1
387 to switch to the .text section. */
389 static void __do_global_ctors_aux (void);
391 __do_global_ctors (void)
394 /* If __main won't actually call __do_global_ctors then it doesn't matter
395 what's inside the function. The inside of __do_global_ctors_aux is
396 called automatically in that case. And the Alliant fx2800 linker
397 crashes on this reference. So prevent the crash. */
398 __do_global_ctors_aux ();
402 asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
404 /* A routine to invoke all of the global constructors upon entry to the
405 program. We put this into the .init section (for systems that have
406 such a thing) so that we can properly perform the construction of
407 file-scope static-storage C++ objects within shared libraries. */
409 static void __attribute__((used))
410 __do_global_ctors_aux (void) /* prologue goes in .init section */
412 FORCE_CODE_SECTION_ALIGN /* explicit align before switch to .text */
413 asm (TEXT_SECTION_ASM_OP); /* don't put epilogue and body in .init */
414 DO_GLOBAL_CTORS_BODY;
415 atexit (__do_global_dtors);
418 #endif /* OBJECT_FORMAT_ELF */
420 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
422 extern void __do_global_dtors (void);
424 /* This case is used by the Irix 6 port, which supports named sections but
425 not an SVR4-style .fini section. __do_global_dtors can be non-static
426 in this case because we protect it with -hidden_symbol. */
429 __do_global_dtors (void)
432 for (p = __DTOR_LIST__ + 1; (f = *p); p++)
435 #ifdef USE_EH_FRAME_REGISTRY
436 if (__deregister_frame_info)
437 __deregister_frame_info (__EH_FRAME_BEGIN__);
441 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
442 /* A helper function for __do_global_ctors, which is in crtend.o. Here
443 in crtbegin.o, we can reference a couple of symbols not visible there.
444 Plus, since we're before libgcc.a, we have no problems referencing
445 functions from there. */
447 __do_global_ctors_1(void)
449 #ifdef USE_EH_FRAME_REGISTRY
450 static struct object object;
451 if (__register_frame_info)
452 __register_frame_info (__EH_FRAME_BEGIN__, &object);
454 #ifdef JCR_SECTION_NAME
457 void (*register_classes) (void *) = _Jv_RegisterClasses;
458 __asm ("" : "+r" (register_classes));
459 if (register_classes)
460 register_classes (__JCR_LIST__);
464 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
466 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
467 #error "What are you doing with crtstuff.c, then?"
470 #elif defined(CRT_END) /* ! CRT_BEGIN */
472 /* Put a word containing zero at the end of each of our two lists of function
473 addresses. Note that the words defined here go into the .ctors and .dtors
474 sections of the crtend.o file, and since that file is always linked in
475 last, these words naturally end up at the very ends of the two lists
476 contained in these two sections. */
480 #elif defined(CTORS_SECTION_ASM_OP)
481 /* Hack: force cc1 to switch to .data section early, so that assembling
482 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */
483 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
484 asm (CTORS_SECTION_ASM_OP);
485 STATIC func_ptr __CTOR_END__[1]
486 __attribute__((aligned(sizeof(func_ptr))))
489 STATIC func_ptr __CTOR_END__[1]
490 __attribute__((section(".ctors"), aligned(sizeof(func_ptr))))
496 #elif defined(HIDDEN_DTOR_LIST_END)
497 #ifdef DTORS_SECTION_ASM_OP
498 asm (DTORS_SECTION_ASM_OP);
500 func_ptr __DTOR_END__[1]
501 __attribute__ ((unused,
502 #ifndef DTORS_SECTION_ASM_OP
505 aligned(sizeof(func_ptr)), visibility ("hidden")))
507 #elif defined(DTORS_SECTION_ASM_OP)
508 asm (DTORS_SECTION_ASM_OP);
509 STATIC func_ptr __DTOR_END__[1]
510 __attribute__ ((unused, aligned(sizeof(func_ptr))))
513 STATIC func_ptr __DTOR_END__[1]
514 __attribute__((unused, section(".dtors"), aligned(sizeof(func_ptr))))
518 #ifdef EH_FRAME_SECTION_NAME
519 /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
520 this would be the 'length' field in a real FDE. */
521 # if __INT_MAX__ == 2147483647
523 # elif __LONG_MAX__ == 2147483647
525 # elif __SHRT_MAX__ == 2147483647
528 # error "Missing a 4 byte integer"
530 STATIC EH_FRAME_SECTION_CONST int32 __FRAME_END__[]
531 __attribute__ ((unused, section(EH_FRAME_SECTION_NAME),
532 aligned(sizeof(int32))))
534 #endif /* EH_FRAME_SECTION_NAME */
536 #ifdef JCR_SECTION_NAME
537 /* Null terminate the .jcr section array. */
538 STATIC void *__JCR_END__[1]
539 __attribute__ ((unused, section(JCR_SECTION_NAME),
540 aligned(sizeof(void *))))
542 #endif /* JCR_SECTION_NAME */
544 #ifdef INIT_ARRAY_SECTION_ASM_OP
546 /* If we are using .init_array, there is nothing to do. */
548 #elif defined(INIT_SECTION_ASM_OP)
550 #ifdef OBJECT_FORMAT_ELF
551 static void __attribute__((used))
552 __do_global_ctors_aux (void)
555 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
559 /* Stick a call to __do_global_ctors_aux into the .init section. */
560 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, __do_global_ctors_aux)
561 #else /* OBJECT_FORMAT_ELF */
563 /* Stick the real initialization code, followed by a normal sort of
564 function epilogue at the very end of the .init section for this
565 entire root executable file or for this entire shared library file.
567 Note that we use some tricks here to get *just* the body and just
568 a function epilogue (but no function prologue) into the .init
569 section of the crtend.o file. Specifically, we switch to the .text
570 section, start to define a function, and then we switch to the .init
571 section just before the body code.
573 Earlier on, we put the corresponding function prologue into the .init
574 section of the crtbegin.o file (which will be linked in first).
576 Note that we want to invoke all constructors for C++ file-scope static-
577 storage objects AFTER any other possible initialization actions which
578 may be performed by the code in the .init section contributions made by
579 other libraries, etc. That's because those other initializations may
580 include setup operations for very primitive things (e.g. initializing
581 the state of the floating-point coprocessor, etc.) which should be done
582 before we start to execute any of the user's code. */
585 __do_global_ctors_aux (void) /* prologue goes in .text section */
587 asm (INIT_SECTION_ASM_OP);
588 DO_GLOBAL_CTORS_BODY;
589 atexit (__do_global_dtors);
590 } /* epilogue and body go in .init section */
592 FORCE_CODE_SECTION_ALIGN
593 asm (TEXT_SECTION_ASM_OP);
595 #endif /* OBJECT_FORMAT_ELF */
597 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
599 extern void __do_global_ctors (void);
601 /* This case is used by the Irix 6 port, which supports named sections but
602 not an SVR4-style .init section. __do_global_ctors can be non-static
603 in this case because we protect it with -hidden_symbol. */
605 __do_global_ctors (void)
608 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
609 __do_global_ctors_1();
611 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
615 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
616 #error "What are you doing with crtstuff.c, then?"
619 #else /* ! CRT_BEGIN && ! CRT_END */
620 #error "One of CRT_BEGIN or CRT_END must be defined."