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, 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 3, or (at your option) any later
14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
19 Under Section 7 of GPL version 3, you are granted additional
20 permissions described in the GCC Runtime Library Exception, version
21 3.1, as published by the Free Software Foundation.
23 You should have received a copy of the GNU General Public License and
24 a copy of the GCC Runtime Library Exception along with this program;
25 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
26 <http://www.gnu.org/licenses/>. */
28 /* This file is a bit like libgcc2.c in that it is compiled
29 multiple times and yields multiple .o files.
31 This file is useful on target machines where the object file format
32 supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE). On
33 such systems, this file allows us to avoid running collect (or any
34 other such slow and painful kludge). Additionally, if the target
35 system supports a .init section, this file allows us to support the
36 linking of C++ code with a non-C++ main program.
38 Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then
39 this file *will* make use of the .init section. If that symbol is
40 not defined however, then the .init section will not be used.
42 Currently, only ELF and COFF are supported. It is likely however that
43 ROSE could also be supported, if someone was willing to do the work to
44 make whatever (small?) adaptations are needed. (Some work may be
45 needed on the ROSE assembler and linker also.)
47 This file must be compiled with gcc. */
49 /* Target machine header files require this define. */
52 /* FIXME: Including auto-host is incorrect, but until we have
53 identified the set of defines that need to go into auto-target.h,
54 this will have to do. */
55 #include "auto-host.h"
64 #include "coretypes.h"
66 #include "unwind-dw2-fde.h"
68 #ifndef FORCE_CODE_SECTION_ALIGN
69 # define FORCE_CODE_SECTION_ALIGN
72 #ifndef CRT_CALL_STATIC_FUNCTION
73 # define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC) \
74 static void __attribute__((__used__)) \
75 call_ ## FUNC (void) \
79 FORCE_CODE_SECTION_ALIGN \
80 asm (TEXT_SECTION_ASM_OP); \
84 #if defined(OBJECT_FORMAT_ELF) \
85 && !defined(OBJECT_FORMAT_FLAT) \
86 && defined(HAVE_LD_EH_FRAME_HDR) \
87 && !defined(inhibit_libc) && !defined(CRTSTUFFT_O) \
88 && defined(__GLIBC__) && __GLIBC__ >= 2
90 /* uClibc pretends to be glibc 2.2 and DT_CONFIG is defined in its link.h.
91 But it doesn't use PT_GNU_EH_FRAME ELF segment currently. */
92 # if !defined(__UCLIBC__) \
93 && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \
94 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG)))
95 # define USE_PT_GNU_EH_FRAME
98 #if defined(EH_FRAME_SECTION_NAME) && !defined(USE_PT_GNU_EH_FRAME)
99 # define USE_EH_FRAME_REGISTRY
101 #if defined(EH_FRAME_SECTION_NAME) && EH_TABLES_CAN_BE_READ_ONLY
102 # define EH_FRAME_SECTION_CONST const
104 # define EH_FRAME_SECTION_CONST
107 #if !defined(DTOR_LIST_END) && defined(OBJECT_FORMAT_ELF) \
108 && defined(HAVE_GAS_HIDDEN) && !defined(FINI_ARRAY_SECTION_ASM_OP)
109 # define HIDDEN_DTOR_LIST_END
112 /* We do not want to add the weak attribute to the declarations of these
113 routines in unwind-dw2-fde.h because that will cause the definition of
114 these symbols to be weak as well.
116 This exposes a core issue, how to handle creating weak references vs
117 how to create weak definitions. Either we have to have the definition
118 of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or
119 have a second declaration if we want a function's references to be weak,
120 but not its definition.
122 Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until
123 one thinks about scaling to larger problems -- i.e., the condition under
124 which TARGET_WEAK_ATTRIBUTE is active will eventually get far too
127 So, we take an approach similar to #pragma weak -- we have a second
128 declaration for functions that we want to have weak references.
130 Neither way is particularly good. */
132 /* References to __register_frame_info and __deregister_frame_info should
133 be weak in this file if at all possible. */
134 extern void __register_frame_info (const void *, struct object *)
135 TARGET_ATTRIBUTE_WEAK;
136 extern void __register_frame_info_bases (const void *, struct object *,
138 TARGET_ATTRIBUTE_WEAK;
139 extern void *__deregister_frame_info (const void *)
140 TARGET_ATTRIBUTE_WEAK;
141 extern void *__deregister_frame_info_bases (const void *)
142 TARGET_ATTRIBUTE_WEAK;
143 extern void __do_global_ctors_1 (void);
145 /* Likewise for _Jv_RegisterClasses. */
146 extern void _Jv_RegisterClasses (void *) TARGET_ATTRIBUTE_WEAK;
148 #ifdef OBJECT_FORMAT_ELF
150 /* Declare a pointer to void function type. */
151 typedef void (*func_ptr) (void);
152 #define STATIC static
154 #else /* OBJECT_FORMAT_ELF */
156 #include "gbl-ctors.h"
160 #endif /* OBJECT_FORMAT_ELF */
164 /* NOTE: In order to be able to support SVR4 shared libraries, we arrange
165 to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__,
166 __DTOR_END__ } per root executable and also one set of these symbols
167 per shared library. So in any given whole process image, we may have
168 multiple definitions of each of these symbols. In order to prevent
169 these definitions from conflicting with one another, and in order to
170 ensure that the proper lists are used for the initialization/finalization
171 of each individual shared library (respectively), we give these symbols
172 only internal (i.e. `static') linkage, and we also make it a point to
173 refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
174 symbol in crtbegin.o, where they are defined. */
176 /* The -1 is a flag to __do_global_[cd]tors indicating that this table
177 does not start with a count of elements. */
178 #ifdef CTOR_LIST_BEGIN
180 #elif defined(CTORS_SECTION_ASM_OP)
181 /* Hack: force cc1 to switch to .data section early, so that assembling
182 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */
183 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
184 asm (CTORS_SECTION_ASM_OP);
185 STATIC func_ptr __CTOR_LIST__[1]
186 __attribute__ ((__unused__, aligned(sizeof(func_ptr))))
187 = { (func_ptr) (-1) };
189 STATIC func_ptr __CTOR_LIST__[1]
190 __attribute__ ((__unused__, section(".ctors"), aligned(sizeof(func_ptr))))
191 = { (func_ptr) (-1) };
192 #endif /* __CTOR_LIST__ alternatives */
194 #ifdef DTOR_LIST_BEGIN
196 #elif defined(DTORS_SECTION_ASM_OP)
197 asm (DTORS_SECTION_ASM_OP);
198 STATIC func_ptr __DTOR_LIST__[1]
199 __attribute__ ((aligned(sizeof(func_ptr))))
200 = { (func_ptr) (-1) };
202 STATIC func_ptr __DTOR_LIST__[1]
203 __attribute__((section(".dtors"), aligned(sizeof(func_ptr))))
204 = { (func_ptr) (-1) };
205 #endif /* __DTOR_LIST__ alternatives */
207 #ifdef USE_EH_FRAME_REGISTRY
208 /* Stick a label at the beginning of the frame unwind info so we can register
209 and deregister it with the exception handling library code. */
210 STATIC EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
211 __attribute__((section(EH_FRAME_SECTION_NAME), aligned(4)))
213 #endif /* USE_EH_FRAME_REGISTRY */
215 #ifdef JCR_SECTION_NAME
216 /* Stick a label at the beginning of the java class registration info
217 so we can register them properly. */
218 STATIC void *__JCR_LIST__[]
219 __attribute__ ((unused, section(JCR_SECTION_NAME), aligned(sizeof(void*))))
221 #endif /* JCR_SECTION_NAME */
223 #if defined(INIT_SECTION_ASM_OP) || defined(INIT_ARRAY_SECTION_ASM_OP)
225 #ifdef OBJECT_FORMAT_ELF
227 /* Declare the __dso_handle variable. It should have a unique value
228 in every shared-object; in a main program its value is zero. The
229 object should in any case be protected. This means the instance
230 in one DSO or the main program is not used in another object. The
231 dynamic linker takes care of this. */
233 #ifdef TARGET_LIBGCC_SDATA_SECTION
234 extern void *__dso_handle __attribute__ ((__section__ (TARGET_LIBGCC_SDATA_SECTION)));
236 #ifdef HAVE_GAS_HIDDEN
237 extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
240 void *__dso_handle = &__dso_handle;
242 void *__dso_handle = 0;
245 /* The __cxa_finalize function may not be available so we use only a
247 extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK;
249 /* Run all the global destructors on exit from the program. */
251 /* Some systems place the number of pointers in the first word of the
252 table. On SVR4 however, that word is -1. In all cases, the table is
253 null-terminated. On SVR4, we start from the beginning of the list and
254 invoke each per-compilation-unit destructor routine in order
255 until we find that null.
257 Note that this function MUST be static. There will be one of these
258 functions in each root executable and one in each shared library, but
259 although they all have the same code, each one is unique in that it
260 refers to one particular associated `__DTOR_LIST__' which belongs to the
261 same particular root executable or shared library file.
263 On some systems, this routine is run more than once from the .fini,
264 when exit is called recursively, so we arrange to remember where in
265 the list we left off processing, and we resume at that point,
266 should we be re-invoked. */
268 static void __attribute__((used))
269 __do_global_dtors_aux (void)
271 static _Bool completed;
273 if (__builtin_expect (completed, 0))
278 __cxa_finalize (__dso_handle);
281 #ifdef FINI_ARRAY_SECTION_ASM_OP
282 /* If we are using .fini_array then destructors will be run via that
284 #elif defined(HIDDEN_DTOR_LIST_END)
286 /* Safer version that makes sure only .dtors function pointers are
287 called even if the static variable is maliciously changed. */
288 extern func_ptr __DTOR_END__[] __attribute__((visibility ("hidden")));
289 static size_t dtor_idx;
290 const size_t max_idx = __DTOR_END__ - __DTOR_LIST__ - 1;
293 while (dtor_idx < max_idx)
295 f = __DTOR_LIST__[++dtor_idx];
299 #else /* !defined (FINI_ARRAY_SECTION_ASM_OP) */
301 static func_ptr *p = __DTOR_LIST__ + 1;
310 #endif /* !defined(FINI_ARRAY_SECTION_ASM_OP) */
312 #ifdef USE_EH_FRAME_REGISTRY
313 #ifdef CRT_GET_RFIB_DATA
314 /* If we used the new __register_frame_info_bases interface,
315 make sure that we deregister from the same place. */
316 if (__deregister_frame_info_bases)
317 __deregister_frame_info_bases (__EH_FRAME_BEGIN__);
319 if (__deregister_frame_info)
320 __deregister_frame_info (__EH_FRAME_BEGIN__);
327 /* Stick a call to __do_global_dtors_aux into the .fini section. */
328 #ifdef FINI_SECTION_ASM_OP
329 CRT_CALL_STATIC_FUNCTION (FINI_SECTION_ASM_OP, __do_global_dtors_aux)
330 #else /* !defined(FINI_SECTION_ASM_OP) */
331 static func_ptr __do_global_dtors_aux_fini_array_entry[]
332 __attribute__ ((__unused__, section(".fini_array")))
333 = { __do_global_dtors_aux };
334 #endif /* !defined(FINI_SECTION_ASM_OP) */
336 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
337 /* Stick a call to __register_frame_info into the .init section. For some
338 reason calls with no arguments work more reliably in .init, so stick the
339 call in another function. */
341 static void __attribute__((used))
344 #ifdef USE_EH_FRAME_REGISTRY
345 static struct object object;
346 #ifdef CRT_GET_RFIB_DATA
349 CRT_GET_RFIB_DATA (dbase);
350 if (__register_frame_info_bases)
351 __register_frame_info_bases (__EH_FRAME_BEGIN__, &object, tbase, dbase);
353 if (__register_frame_info)
354 __register_frame_info (__EH_FRAME_BEGIN__, &object);
355 #endif /* CRT_GET_RFIB_DATA */
356 #endif /* USE_EH_FRAME_REGISTRY */
357 #ifdef JCR_SECTION_NAME
360 void (*register_classes) (void *) = _Jv_RegisterClasses;
361 __asm ("" : "+r" (register_classes));
362 if (register_classes)
363 register_classes (__JCR_LIST__);
365 #endif /* JCR_SECTION_NAME */
368 #ifdef INIT_SECTION_ASM_OP
369 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, frame_dummy)
370 #else /* defined(INIT_SECTION_ASM_OP) */
371 static func_ptr __frame_dummy_init_array_entry[]
372 __attribute__ ((__unused__, section(".init_array")))
374 #endif /* !defined(INIT_SECTION_ASM_OP) */
375 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
377 #else /* OBJECT_FORMAT_ELF */
379 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
380 and once in crtend.o). It must be declared static to avoid a link
381 error. Here, we define __do_global_ctors as an externally callable
382 function. It is externally callable so that __main can invoke it when
383 INVOKE__main is defined. This has the additional effect of forcing cc1
384 to switch to the .text section. */
386 static void __do_global_ctors_aux (void);
388 __do_global_ctors (void)
391 /* If __main won't actually call __do_global_ctors then it doesn't matter
392 what's inside the function. The inside of __do_global_ctors_aux is
393 called automatically in that case. And the Alliant fx2800 linker
394 crashes on this reference. So prevent the crash. */
395 __do_global_ctors_aux ();
399 asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
401 /* A routine to invoke all of the global constructors upon entry to the
402 program. We put this into the .init section (for systems that have
403 such a thing) so that we can properly perform the construction of
404 file-scope static-storage C++ objects within shared libraries. */
406 static void __attribute__((used))
407 __do_global_ctors_aux (void) /* prologue goes in .init section */
409 FORCE_CODE_SECTION_ALIGN /* explicit align before switch to .text */
410 asm (TEXT_SECTION_ASM_OP); /* don't put epilogue and body in .init */
411 DO_GLOBAL_CTORS_BODY;
412 atexit (__do_global_dtors);
415 #endif /* OBJECT_FORMAT_ELF */
417 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
419 extern void __do_global_dtors (void);
421 /* This case is used by the Irix 6 port, which supports named sections but
422 not an SVR4-style .fini section. __do_global_dtors can be non-static
423 in this case because we protect it with -hidden_symbol. */
426 __do_global_dtors (void)
429 for (p = __DTOR_LIST__ + 1; (f = *p); p++)
432 #ifdef USE_EH_FRAME_REGISTRY
433 if (__deregister_frame_info)
434 __deregister_frame_info (__EH_FRAME_BEGIN__);
438 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
439 /* A helper function for __do_global_ctors, which is in crtend.o. Here
440 in crtbegin.o, we can reference a couple of symbols not visible there.
441 Plus, since we're before libgcc.a, we have no problems referencing
442 functions from there. */
444 __do_global_ctors_1(void)
446 #ifdef USE_EH_FRAME_REGISTRY
447 static struct object object;
448 if (__register_frame_info)
449 __register_frame_info (__EH_FRAME_BEGIN__, &object);
451 #ifdef JCR_SECTION_NAME
454 void (*register_classes) (void *) = _Jv_RegisterClasses;
455 __asm ("" : "+r" (register_classes));
456 if (register_classes)
457 register_classes (__JCR_LIST__);
461 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
463 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
464 #error "What are you doing with crtstuff.c, then?"
467 #elif defined(CRT_END) /* ! CRT_BEGIN */
469 /* Put a word containing zero at the end of each of our two lists of function
470 addresses. Note that the words defined here go into the .ctors and .dtors
471 sections of the crtend.o file, and since that file is always linked in
472 last, these words naturally end up at the very ends of the two lists
473 contained in these two sections. */
477 #elif defined(CTORS_SECTION_ASM_OP)
478 /* Hack: force cc1 to switch to .data section early, so that assembling
479 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */
480 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
481 asm (CTORS_SECTION_ASM_OP);
482 STATIC func_ptr __CTOR_END__[1]
483 __attribute__((aligned(sizeof(func_ptr))))
486 STATIC func_ptr __CTOR_END__[1]
487 __attribute__((section(".ctors"), aligned(sizeof(func_ptr))))
493 #elif defined(HIDDEN_DTOR_LIST_END)
494 #ifdef DTORS_SECTION_ASM_OP
495 asm (DTORS_SECTION_ASM_OP);
497 func_ptr __DTOR_END__[1]
498 __attribute__ ((unused,
499 #ifndef DTORS_SECTION_ASM_OP
502 aligned(sizeof(func_ptr)), visibility ("hidden")))
504 #elif defined(DTORS_SECTION_ASM_OP)
505 asm (DTORS_SECTION_ASM_OP);
506 STATIC func_ptr __DTOR_END__[1]
507 __attribute__ ((unused, aligned(sizeof(func_ptr))))
510 STATIC func_ptr __DTOR_END__[1]
511 __attribute__((unused, section(".dtors"), aligned(sizeof(func_ptr))))
515 #ifdef EH_FRAME_SECTION_NAME
516 /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
517 this would be the 'length' field in a real FDE. */
518 # if __INT_MAX__ == 2147483647
520 # elif __LONG_MAX__ == 2147483647
522 # elif __SHRT_MAX__ == 2147483647
525 # error "Missing a 4 byte integer"
527 STATIC EH_FRAME_SECTION_CONST int32 __FRAME_END__[]
528 __attribute__ ((unused, section(EH_FRAME_SECTION_NAME),
529 aligned(sizeof(int32))))
531 #endif /* EH_FRAME_SECTION_NAME */
533 #ifdef JCR_SECTION_NAME
534 /* Null terminate the .jcr section array. */
535 STATIC void *__JCR_END__[1]
536 __attribute__ ((unused, section(JCR_SECTION_NAME),
537 aligned(sizeof(void *))))
539 #endif /* JCR_SECTION_NAME */
541 #ifdef INIT_ARRAY_SECTION_ASM_OP
543 /* If we are using .init_array, there is nothing to do. */
545 #elif defined(INIT_SECTION_ASM_OP)
547 #ifdef OBJECT_FORMAT_ELF
548 static void __attribute__((used))
549 __do_global_ctors_aux (void)
552 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
556 /* Stick a call to __do_global_ctors_aux into the .init section. */
557 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, __do_global_ctors_aux)
558 #else /* OBJECT_FORMAT_ELF */
560 /* Stick the real initialization code, followed by a normal sort of
561 function epilogue at the very end of the .init section for this
562 entire root executable file or for this entire shared library file.
564 Note that we use some tricks here to get *just* the body and just
565 a function epilogue (but no function prologue) into the .init
566 section of the crtend.o file. Specifically, we switch to the .text
567 section, start to define a function, and then we switch to the .init
568 section just before the body code.
570 Earlier on, we put the corresponding function prologue into the .init
571 section of the crtbegin.o file (which will be linked in first).
573 Note that we want to invoke all constructors for C++ file-scope static-
574 storage objects AFTER any other possible initialization actions which
575 may be performed by the code in the .init section contributions made by
576 other libraries, etc. That's because those other initializations may
577 include setup operations for very primitive things (e.g. initializing
578 the state of the floating-point coprocessor, etc.) which should be done
579 before we start to execute any of the user's code. */
582 __do_global_ctors_aux (void) /* prologue goes in .text section */
584 asm (INIT_SECTION_ASM_OP);
585 DO_GLOBAL_CTORS_BODY;
586 atexit (__do_global_dtors);
587 } /* epilogue and body go in .init section */
589 FORCE_CODE_SECTION_ALIGN
590 asm (TEXT_SECTION_ASM_OP);
592 #endif /* OBJECT_FORMAT_ELF */
594 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
596 extern void __do_global_ctors (void);
598 /* This case is used by the Irix 6 port, which supports named sections but
599 not an SVR4-style .init section. __do_global_ctors can be non-static
600 in this case because we protect it with -hidden_symbol. */
602 __do_global_ctors (void)
605 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
606 __do_global_ctors_1();
608 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
612 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
613 #error "What are you doing with crtstuff.c, then?"
616 #else /* ! CRT_BEGIN && ! CRT_END */
617 #error "One of CRT_BEGIN or CRT_END must be defined."