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,
4 1999, 2000, 2001 Free Software Foundation, Inc.
5 Contributed by Ron Guilmette (rfg@monkeys.com).
7 This file is part of GNU CC.
9 GNU CC is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2, or (at your option)
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 GNU CC is distributed in the hope that it will be useful,
24 but WITHOUT ANY WARRANTY; without even the implied warranty of
25 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
26 GNU General Public License for more details.
28 You should have received a copy of the GNU General Public License
29 along with GNU CC; see the file COPYING. If not, write to
30 the Free Software Foundation, 59 Temple Place - Suite 330,
31 Boston, MA 02111-1307, USA. */
33 /* This file is a bit like libgcc1.c/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 /* It is incorrect to include config.h here, because this file is being
55 compiled for the target, and hence definitions concerning only the host
58 #include "auto-host.h"
61 #include "unwind-dw2-fde.h"
63 #ifndef CRT_CALL_STATIC_FUNCTION
64 # define CRT_CALL_STATIC_FUNCTION(func) func ()
67 /* We do not want to add the weak attribute to the declarations of these
68 routines in unwind-dw2-fde.h because that will cause the definition of
69 these symbols to be weak as well.
71 This exposes a core issue, how to handle creating weak references vs
72 how to create weak definitions. Either we have to have the definition
73 of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or
74 have a second declaration if we want a function's references to be weak,
75 but not its definition.
77 Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until
78 one thinks about scaling to larger problems -- ie, the condition under
79 which TARGET_WEAK_ATTRIBUTE is active will eventually get far too
82 So, we take an approach similar to #pragma weak -- we have a second
83 declaration for functions that we want to have weak references.
85 Neither way is particularly good. */
87 /* References to __register_frame_info and __deregister_frame_info should
88 be weak in this file if at all possible. */
89 extern void __register_frame_info (void *, struct object
*)
90 TARGET_ATTRIBUTE_WEAK
;
91 extern void __register_frame_info_bases (void *, struct object
*,
93 TARGET_ATTRIBUTE_WEAK
;
94 extern void *__deregister_frame_info (void *)
95 TARGET_ATTRIBUTE_WEAK
;
96 extern void *__deregister_frame_info_bases (void *)
97 TARGET_ATTRIBUTE_WEAK
;
99 #ifndef OBJECT_FORMAT_MACHO
101 /* Provide default definitions for the pseudo-ops used to switch to the
102 .ctors and .dtors sections.
104 Note that we want to give these sections the SHF_WRITE attribute
105 because these sections will actually contain data (i.e. tables of
106 addresses of functions in the current root executable or shared library
107 file) and, in the case of a shared library, the relocatable addresses
108 will have to be properly resolved/relocated (and then written into) by
109 the dynamic linker when it actually attaches the given shared library
110 to the executing process. (Note that on SVR4, you may wish to use the
111 `-z text' option to the ELF linker, when building a shared library, as
112 an additional check that you are doing everything right. But if you do
113 use the `-z text' option when building a shared library, you will get
114 errors unless the .ctors and .dtors sections are marked as writable
115 via the SHF_WRITE attribute.)
117 These defaults do not include leading spacing, as they will only be
118 used in asm:s here. */
120 #ifndef CTORS_SECTION_ASM_OP
121 #define CTORS_SECTION_ASM_OP ".section\t.ctors,\"aw\""
123 #ifndef DTORS_SECTION_ASM_OP
124 #define DTORS_SECTION_ASM_OP ".section\t.dtors,\"aw\""
127 #ifdef OBJECT_FORMAT_ELF
129 /* Declare a pointer to void function type. */
130 typedef void (*func_ptr
) (void);
131 #define STATIC static
133 #else /* OBJECT_FORMAT_ELF */
135 #include "gbl-ctors.h"
139 #endif /* OBJECT_FORMAT_ELF */
143 #ifdef INIT_SECTION_ASM_OP
145 #ifdef OBJECT_FORMAT_ELF
147 /* Declare the __dso_handle variable. It should have a unique value
148 in every shared-object; in a main program its value is zero. The
149 object should in any case be protected. This means the instance
150 in one DSO or the main program is not used in another object. The
151 dynamic linker takes care of this. */
153 /* XXX Ideally the following should be implemented using
154 __attribute__ ((__visibility__ ("hidden")))
155 but the __attribute__ support is not yet there. */
156 #ifdef HAVE_GAS_HIDDEN
157 asm (".hidden\t__dso_handle");
161 void *__dso_handle
= &__dso_handle
;
163 void *__dso_handle
= 0;
166 /* The __cxa_finalize function may not be available so we use only a
168 extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK
;
170 /* Run all the global destructors on exit from the program. */
172 /* Some systems place the number of pointers in the first word of the
173 table. On SVR4 however, that word is -1. In all cases, the table is
174 null-terminated. On SVR4, we start from the beginning of the list and
175 invoke each per-compilation-unit destructor routine in order
176 until we find that null.
178 Note that this function MUST be static. There will be one of these
179 functions in each root executable and one in each shared library, but
180 although they all have the same code, each one is unique in that it
181 refers to one particular associated `__DTOR_LIST__' which belongs to the
182 same particular root executable or shared library file.
184 On some systems, this routine is run more than once from the .fini,
185 when exit is called recursively, so we arrange to remember where in
186 the list we left off processing, and we resume at that point,
187 should we be re-invoked. */
189 static char __EH_FRAME_BEGIN__
[];
190 static func_ptr __DTOR_LIST__
[];
192 __do_global_dtors_aux (void)
194 static func_ptr
*p
= __DTOR_LIST__
+ 1;
195 static int completed
;
198 if (__builtin_expect (completed
, 0))
203 __cxa_finalize (__dso_handle
);
212 #ifdef EH_FRAME_SECTION_ASM_OP
213 #if defined(CRT_GET_RFIB_TEXT) || defined(CRT_GET_RFIB_DATA)
214 /* If we used the new __register_frame_info_bases interface,
215 make sure that we deregister from the same place. */
216 if (__deregister_frame_info_bases
)
217 __deregister_frame_info_bases (__EH_FRAME_BEGIN__
);
219 if (__deregister_frame_info
)
220 __deregister_frame_info (__EH_FRAME_BEGIN__
);
228 /* Stick a call to __do_global_dtors_aux into the .fini section. */
230 static void __attribute__ ((__unused__
))
233 asm (FINI_SECTION_ASM_OP
);
234 CRT_CALL_STATIC_FUNCTION (__do_global_dtors_aux
);
235 #ifdef FORCE_FINI_SECTION_ALIGN
236 FORCE_FINI_SECTION_ALIGN
;
238 asm (TEXT_SECTION_ASM_OP
);
241 #ifdef EH_FRAME_SECTION_ASM_OP
242 /* Stick a call to __register_frame_info into the .init section. For some
243 reason calls with no arguments work more reliably in .init, so stick the
244 call in another function. */
249 static struct object object
;
250 #if defined(CRT_GET_RFIB_TEXT) || defined(CRT_GET_RFIB_DATA)
252 #ifdef CRT_GET_RFIB_TEXT
253 CRT_GET_RFIB_TEXT (tbase
);
257 #ifdef CRT_GET_RFIB_DATA
258 CRT_GET_RFIB_DATA (dbase
);
262 if (__register_frame_info_bases
)
263 __register_frame_info_bases (__EH_FRAME_BEGIN__
, &object
, tbase
, dbase
);
265 if (__register_frame_info
)
266 __register_frame_info (__EH_FRAME_BEGIN__
, &object
);
270 static void __attribute__ ((__unused__
))
273 asm (INIT_SECTION_ASM_OP
);
274 CRT_CALL_STATIC_FUNCTION (frame_dummy
);
275 #ifdef FORCE_INIT_SECTION_ALIGN
276 FORCE_INIT_SECTION_ALIGN
;
278 asm (TEXT_SECTION_ASM_OP
);
280 #endif /* EH_FRAME_SECTION_ASM_OP */
282 #else /* OBJECT_FORMAT_ELF */
284 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
285 and once in crtend.o). It must be declared static to avoid a link
286 error. Here, we define __do_global_ctors as an externally callable
287 function. It is externally callable so that __main can invoke it when
288 INVOKE__main is defined. This has the additional effect of forcing cc1
289 to switch to the .text section. */
291 static void __do_global_ctors_aux (void);
293 __do_global_ctors (void)
295 #ifdef INVOKE__main /* If __main won't actually call __do_global_ctors
296 then it doesn't matter what's inside the function.
297 The inside of __do_global_ctors_aux is called
298 automatically in that case.
299 And the Alliant fx2800 linker crashes
300 on this reference. So prevent the crash. */
301 __do_global_ctors_aux ();
305 asm (INIT_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
307 /* On some svr4 systems, the initial .init section preamble code provided in
308 crti.o may do something, such as bump the stack, which we have to
309 undo before we reach the function prologue code for __do_global_ctors
310 (directly below). For such systems, define the macro INIT_SECTION_PREAMBLE
311 to expand into the code needed to undo the actions of the crti.o file. */
313 #ifdef INIT_SECTION_PREAMBLE
314 INIT_SECTION_PREAMBLE
;
317 /* A routine to invoke all of the global constructors upon entry to the
318 program. We put this into the .init section (for systems that have
319 such a thing) so that we can properly perform the construction of
320 file-scope static-storage C++ objects within shared libraries. */
323 __do_global_ctors_aux (void) /* prologue goes in .init section */
325 #ifdef FORCE_INIT_SECTION_ALIGN
326 FORCE_INIT_SECTION_ALIGN
; /* Explicit align before switch to .text */
328 asm (TEXT_SECTION_ASM_OP
); /* don't put epilogue and body in .init */
329 DO_GLOBAL_CTORS_BODY
;
330 atexit (__do_global_dtors
);
333 #endif /* OBJECT_FORMAT_ELF */
335 #else /* defined(INIT_SECTION_ASM_OP) */
337 #ifdef HAS_INIT_SECTION
338 /* This case is used by the Irix 6 port, which supports named sections but
339 not an SVR4-style .fini section. __do_global_dtors can be non-static
340 in this case because we protect it with -hidden_symbol. */
342 static char __EH_FRAME_BEGIN__
[];
343 static func_ptr __DTOR_LIST__
[];
345 __do_global_dtors (void)
348 for (p
= __DTOR_LIST__
+ 1; (f
= *p
); p
++)
351 #ifdef EH_FRAME_SECTION_ASM_OP
352 if (__deregister_frame_info
)
353 __deregister_frame_info (__EH_FRAME_BEGIN__
);
357 #ifdef EH_FRAME_SECTION_ASM_OP
358 /* Define a function here to call __register_frame. crtend.o is linked in
359 after libgcc.a, and hence can't call libgcc.a functions directly. That
360 can lead to unresolved function references. */
364 static struct object object
;
365 if (__register_frame_info
)
366 __register_frame_info (__EH_FRAME_BEGIN__
, &object
);
371 #endif /* defined(INIT_SECTION_ASM_OP) */
373 /* Force cc1 to switch to .data section. */
374 static func_ptr force_to_data
[1] __attribute__ ((__unused__
)) = { };
376 /* NOTE: In order to be able to support SVR4 shared libraries, we arrange
377 to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__,
378 __DTOR_END__ } per root executable and also one set of these symbols
379 per shared library. So in any given whole process image, we may have
380 multiple definitions of each of these symbols. In order to prevent
381 these definitions from conflicting with one another, and in order to
382 ensure that the proper lists are used for the initialization/finalization
383 of each individual shared library (respectively), we give these symbols
384 only internal (i.e. `static') linkage, and we also make it a point to
385 refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
386 symbol in crtbegin.o, where they are defined. */
388 /* The -1 is a flag to __do_global_[cd]tors
389 indicating that this table does not start with a count of elements. */
390 #ifdef CTOR_LIST_BEGIN
393 asm (CTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
394 STATIC func_ptr __CTOR_LIST__
[1] __attribute__ ((__unused__
))
395 = { (func_ptr
) (-1) };
398 #ifdef DTOR_LIST_BEGIN
401 asm (DTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
402 STATIC func_ptr __DTOR_LIST__
[1] = { (func_ptr
) (-1) };
405 #ifdef EH_FRAME_SECTION_ASM_OP
406 /* Stick a label at the beginning of the frame unwind info so we can register
407 and deregister it with the exception handling library code. */
409 asm (EH_FRAME_SECTION_ASM_OP
);
410 #ifdef INIT_SECTION_ASM_OP
413 char __EH_FRAME_BEGIN__
[] = { };
414 #endif /* EH_FRAME_SECTION_ASM_OP */
416 #endif /* defined(CRT_BEGIN) */
420 #ifdef INIT_SECTION_ASM_OP
422 #ifdef OBJECT_FORMAT_ELF
424 static func_ptr __CTOR_END__
[];
426 __do_global_ctors_aux (void)
429 for (p
= __CTOR_END__
- 1; *p
!= (func_ptr
) -1; p
--)
433 /* Stick a call to __do_global_ctors_aux into the .init section. */
435 static void __attribute__ ((__unused__
))
438 asm (INIT_SECTION_ASM_OP
);
439 CRT_CALL_STATIC_FUNCTION (__do_global_ctors_aux
);
440 #ifdef FORCE_INIT_SECTION_ALIGN
441 FORCE_INIT_SECTION_ALIGN
;
443 asm (TEXT_SECTION_ASM_OP
);
444 #ifdef CRT_END_INIT_DUMMY
449 #else /* OBJECT_FORMAT_ELF */
451 /* Stick the real initialization code, followed by a normal sort of
452 function epilogue at the very end of the .init section for this
453 entire root executable file or for this entire shared library file.
455 Note that we use some tricks here to get *just* the body and just
456 a function epilogue (but no function prologue) into the .init
457 section of the crtend.o file. Specifically, we switch to the .text
458 section, start to define a function, and then we switch to the .init
459 section just before the body code.
461 Earlier on, we put the corresponding function prologue into the .init
462 section of the crtbegin.o file (which will be linked in first).
464 Note that we want to invoke all constructors for C++ file-scope static-
465 storage objects AFTER any other possible initialization actions which
466 may be performed by the code in the .init section contributions made by
467 other libraries, etc. That's because those other initializations may
468 include setup operations for very primitive things (e.g. initializing
469 the state of the floating-point coprocessor, etc.) which should be done
470 before we start to execute any of the user's code. */
473 __do_global_ctors_aux (void) /* prologue goes in .text section */
475 asm (INIT_SECTION_ASM_OP
);
476 DO_GLOBAL_CTORS_BODY
;
477 atexit (__do_global_dtors
);
478 } /* epilogue and body go in .init section */
480 #ifdef FORCE_INIT_SECTION_ALIGN
481 FORCE_INIT_SECTION_ALIGN
;
484 asm (TEXT_SECTION_ASM_OP
);
486 #endif /* OBJECT_FORMAT_ELF */
488 #else /* defined(INIT_SECTION_ASM_OP) */
490 #ifdef HAS_INIT_SECTION
491 /* This case is used by the Irix 6 port, which supports named sections but
492 not an SVR4-style .init section. __do_global_ctors can be non-static
493 in this case because we protect it with -hidden_symbol. */
494 static func_ptr __CTOR_END__
[];
495 #ifdef EH_FRAME_SECTION_ASM_OP
496 extern void __frame_dummy (void);
499 __do_global_ctors (void)
502 #ifdef EH_FRAME_SECTION_ASM_OP
505 for (p
= __CTOR_END__
- 1; *p
!= (func_ptr
) -1; p
--)
510 #endif /* defined(INIT_SECTION_ASM_OP) */
512 /* Force cc1 to switch to .data section. */
513 static func_ptr force_to_data
[1] __attribute__ ((__unused__
)) = { };
515 /* Put a word containing zero at the end of each of our two lists of function
516 addresses. Note that the words defined here go into the .ctors and .dtors
517 sections of the crtend.o file, and since that file is always linked in
518 last, these words naturally end up at the very ends of the two lists
519 contained in these two sections. */
524 asm (CTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
525 STATIC func_ptr __CTOR_END__
[1] = { (func_ptr
) 0 };
531 asm (DTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
532 STATIC func_ptr __DTOR_END__
[1] __attribute__ ((__unused__
))
536 #ifdef EH_FRAME_SECTION_ASM_OP
537 /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
538 this would be the 'length' field in a real FDE. */
540 typedef unsigned int ui32
__attribute__ ((mode (SI
)));
541 asm (EH_FRAME_SECTION_ASM_OP
);
542 STATIC ui32 __FRAME_END__
[] __attribute__ ((__unused__
)) = { 0 };
543 #endif /* EH_FRAME_SECTION */
545 #endif /* defined(CRT_END) */
547 #else /* OBJECT_FORMAT_MACHO */
549 /* For Mach-O format executables, we assume that the system's runtime is
550 smart enough to handle constructors and destructors, but doesn't have
551 an init section (if it can't even handle constructors/destructors
552 you should be using INVOKE__main, not crtstuff). All we need to do
553 is install/deinstall the frame information for exceptions. We do this
554 by putting a constructor in crtbegin.o and a destructor in crtend.o.
556 crtend.o also puts in the terminating zero in the frame information
559 /* The crtstuff for other object formats use the symbol __EH_FRAME_BEGIN__
560 to figure out the start of the exception frame, but here we use
561 getsectbynamefromheader to find this value. Either method would work,
562 but this method avoids creating any global symbols, which seems
565 #include <mach-o/ldsyms.h>
566 extern const struct section
*
567 getsectbynamefromheader (const struct mach_header
*,
568 const char *, const char *);
572 static void __reg_frame_ctor (void) __attribute__ ((constructor
));
575 __reg_frame_ctor (void)
577 static struct object object
;
578 const struct section
*eh_frame
;
580 eh_frame
= getsectbynamefromheader (&_mh_execute_header
,
581 "__TEXT", "__eh_frame");
582 __register_frame_info ((void *) eh_frame
->addr
, &object
);
585 #endif /* CRT_BEGIN */
589 static void __dereg_frame_dtor (void) __attribute__ ((destructor
));
592 __dereg_frame_dtor (void)
594 const struct section
*eh_frame
;
596 eh_frame
= getsectbynamefromheader (&_mh_execute_header
,
597 "__TEXT", "__eh_frame");
598 __deregister_frame_info ((void *) eh_frame
->addr
);
601 /* Terminate the frame section with a final zero. */
603 /* Force cc1 to switch to .data section. */
604 static void * force_to_data
[1] __attribute__ ((__unused__
)) = { };
606 typedef unsigned int ui32
__attribute__ ((mode (SI
)));
607 asm (EH_FRAME_SECTION_ASM_OP
);
608 static ui32 __FRAME_END__
[] __attribute__ ((__unused__
)) = { 0 };
612 #endif /* OBJECT_FORMAT_MACHO */