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 /* We include auto-host.h here to get HAVE_GAS_HIDDEN. This is
59 supposedly valid even though this is a "target" file. */
60 #include "auto-host.h"
65 #ifndef CRT_CALL_STATIC_FUNCTION
66 # define CRT_CALL_STATIC_FUNCTION(func) func ()
69 /* We do not want to add the weak attribute to the declarations of these
70 routines in frame.h because that will cause the definition of these
71 symbols to be weak as well.
73 This exposes a core issue, how to handle creating weak references vs
74 how to create weak definitions. Either we have to have the definition
75 of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or
76 have a second declaration if we want a function's references to be weak,
77 but not its definition.
79 Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until
80 one thinks about scaling to larger problems -- ie, the condition under
81 which TARGET_WEAK_ATTRIBUTE is active will eventually get far too
84 So, we take an approach similar to #pragma weak -- we have a second
85 declaration for functions that we want to have weak references.
87 Neither way is particularly good. */
89 /* References to __register_frame_info and __deregister_frame_info should
90 be weak in this file if at all possible. */
91 extern void __register_frame_info (void *, struct object
*)
92 TARGET_ATTRIBUTE_WEAK
;
94 extern void *__deregister_frame_info (void *)
95 TARGET_ATTRIBUTE_WEAK
;
97 #ifndef OBJECT_FORMAT_MACHO
99 /* Provide default definitions for the pseudo-ops used to switch to the
100 .ctors and .dtors sections.
102 Note that we want to give these sections the SHF_WRITE attribute
103 because these sections will actually contain data (i.e. tables of
104 addresses of functions in the current root executable or shared library
105 file) and, in the case of a shared library, the relocatable addresses
106 will have to be properly resolved/relocated (and then written into) by
107 the dynamic linker when it actually attaches the given shared library
108 to the executing process. (Note that on SVR4, you may wish to use the
109 `-z text' option to the ELF linker, when building a shared library, as
110 an additional check that you are doing everything right. But if you do
111 use the `-z text' option when building a shared library, you will get
112 errors unless the .ctors and .dtors sections are marked as writable
113 via the SHF_WRITE attribute.)
115 These defaults do not include leading spacing, as they will only be
116 used in asm:s here. */
118 #ifndef CTORS_SECTION_ASM_OP
119 #define CTORS_SECTION_ASM_OP ".section\t.ctors,\"aw\""
121 #ifndef DTORS_SECTION_ASM_OP
122 #define DTORS_SECTION_ASM_OP ".section\t.dtors,\"aw\""
125 #ifdef OBJECT_FORMAT_ELF
127 /* Declare a pointer to void function type. */
128 typedef void (*func_ptr
) (void);
129 #define STATIC static
131 #else /* OBJECT_FORMAT_ELF */
133 #include "gbl-ctors.h"
137 #endif /* OBJECT_FORMAT_ELF */
141 #ifdef INIT_SECTION_ASM_OP
143 #ifdef OBJECT_FORMAT_ELF
145 /* Declare the __dso_handle variable. It should have a unique value
146 in every shared-object; in a main program its value is zero. The
147 object should in any case be protected. This means the instance
148 in one DSO or the main program is not used in another object. The
149 dynamic linker takes care of this. */
151 /* XXX Ideally the following should be implemented using
152 __attribute__ ((__visibility__ ("hidden")))
153 but the __attribute__ support is not yet there. */
154 #ifdef HAVE_GAS_HIDDEN
155 asm (".hidden\t__dso_handle");
159 void *__dso_handle
= &__dso_handle
;
161 void *__dso_handle
= 0;
164 /* The __cxa_finalize function may not be available so we use only a
166 extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK
;
168 /* Run all the global destructors on exit from the program. */
170 /* Some systems place the number of pointers in the first word of the
171 table. On SVR4 however, that word is -1. In all cases, the table is
172 null-terminated. On SVR4, we start from the beginning of the list and
173 invoke each per-compilation-unit destructor routine in order
174 until we find that null.
176 Note that this function MUST be static. There will be one of these
177 functions in each root executable and one in each shared library, but
178 although they all have the same code, each one is unique in that it
179 refers to one particular associated `__DTOR_LIST__' which belongs to the
180 same particular root executable or shared library file.
182 On some systems, this routine is run more than once from the .fini,
183 when exit is called recursively, so we arrange to remember where in
184 the list we left off processing, and we resume at that point,
185 should we be re-invoked. */
187 static char __EH_FRAME_BEGIN__
[];
188 static func_ptr __DTOR_LIST__
[];
190 __do_global_dtors_aux (void)
192 static func_ptr
*p
= __DTOR_LIST__
+ 1;
193 static int completed
= 0;
200 __cxa_finalize (__dso_handle
);
209 #ifdef EH_FRAME_SECTION_ASM_OP
210 if (__deregister_frame_info
)
211 __deregister_frame_info (__EH_FRAME_BEGIN__
);
217 /* Stick a call to __do_global_dtors_aux into the .fini section. */
219 static void __attribute__ ((__unused__
))
222 asm (FINI_SECTION_ASM_OP
);
223 CRT_CALL_STATIC_FUNCTION (__do_global_dtors_aux
);
224 #ifdef FORCE_FINI_SECTION_ALIGN
225 FORCE_FINI_SECTION_ALIGN
;
227 asm (TEXT_SECTION_ASM_OP
);
230 #ifdef EH_FRAME_SECTION_ASM_OP
231 /* Stick a call to __register_frame_info into the .init section. For some
232 reason calls with no arguments work more reliably in .init, so stick the
233 call in another function. */
238 static struct object object
;
239 if (__register_frame_info
)
240 __register_frame_info (__EH_FRAME_BEGIN__
, &object
);
243 static void __attribute__ ((__unused__
))
246 asm (INIT_SECTION_ASM_OP
);
247 CRT_CALL_STATIC_FUNCTION (frame_dummy
);
248 #ifdef FORCE_INIT_SECTION_ALIGN
249 FORCE_INIT_SECTION_ALIGN
;
251 asm (TEXT_SECTION_ASM_OP
);
253 #endif /* EH_FRAME_SECTION_ASM_OP */
255 #else /* OBJECT_FORMAT_ELF */
257 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
258 and once in crtend.o). It must be declared static to avoid a link
259 error. Here, we define __do_global_ctors as an externally callable
260 function. It is externally callable so that __main can invoke it when
261 INVOKE__main is defined. This has the additional effect of forcing cc1
262 to switch to the .text section. */
264 static void __do_global_ctors_aux (void);
266 __do_global_ctors (void)
268 #ifdef INVOKE__main /* If __main won't actually call __do_global_ctors
269 then it doesn't matter what's inside the function.
270 The inside of __do_global_ctors_aux is called
271 automatically in that case.
272 And the Alliant fx2800 linker crashes
273 on this reference. So prevent the crash. */
274 __do_global_ctors_aux ();
278 asm (INIT_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
280 /* On some svr4 systems, the initial .init section preamble code provided in
281 crti.o may do something, such as bump the stack, which we have to
282 undo before we reach the function prologue code for __do_global_ctors
283 (directly below). For such systems, define the macro INIT_SECTION_PREAMBLE
284 to expand into the code needed to undo the actions of the crti.o file. */
286 #ifdef INIT_SECTION_PREAMBLE
287 INIT_SECTION_PREAMBLE
;
290 /* A routine to invoke all of the global constructors upon entry to the
291 program. We put this into the .init section (for systems that have
292 such a thing) so that we can properly perform the construction of
293 file-scope static-storage C++ objects within shared libraries. */
296 __do_global_ctors_aux (void) /* prologue goes in .init section */
298 #ifdef FORCE_INIT_SECTION_ALIGN
299 FORCE_INIT_SECTION_ALIGN
; /* Explicit align before switch to .text */
301 asm (TEXT_SECTION_ASM_OP
); /* don't put epilogue and body in .init */
302 DO_GLOBAL_CTORS_BODY
;
303 atexit (__do_global_dtors
);
306 #endif /* OBJECT_FORMAT_ELF */
308 #else /* defined(INIT_SECTION_ASM_OP) */
310 #ifdef HAS_INIT_SECTION
311 /* This case is used by the Irix 6 port, which supports named sections but
312 not an SVR4-style .fini section. __do_global_dtors can be non-static
313 in this case because we protect it with -hidden_symbol. */
315 static char __EH_FRAME_BEGIN__
[];
316 static func_ptr __DTOR_LIST__
[];
318 __do_global_dtors (void)
321 for (p
= __DTOR_LIST__
+ 1; *p
; p
++)
324 #ifdef EH_FRAME_SECTION_ASM_OP
325 if (__deregister_frame_info
)
326 __deregister_frame_info (__EH_FRAME_BEGIN__
);
330 #ifdef EH_FRAME_SECTION_ASM_OP
331 /* Define a function here to call __register_frame. crtend.o is linked in
332 after libgcc.a, and hence can't call libgcc.a functions directly. That
333 can lead to unresolved function references. */
337 static struct object object
;
338 if (__register_frame_info
)
339 __register_frame_info (__EH_FRAME_BEGIN__
, &object
);
344 #endif /* defined(INIT_SECTION_ASM_OP) */
346 /* Force cc1 to switch to .data section. */
347 static func_ptr force_to_data
[1] __attribute__ ((__unused__
)) = { };
349 /* NOTE: In order to be able to support SVR4 shared libraries, we arrange
350 to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__,
351 __DTOR_END__ } per root executable and also one set of these symbols
352 per shared library. So in any given whole process image, we may have
353 multiple definitions of each of these symbols. In order to prevent
354 these definitions from conflicting with one another, and in order to
355 ensure that the proper lists are used for the initialization/finalization
356 of each individual shared library (respectively), we give these symbols
357 only internal (i.e. `static') linkage, and we also make it a point to
358 refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
359 symbol in crtbegin.o, where they are defined. */
361 /* The -1 is a flag to __do_global_[cd]tors
362 indicating that this table does not start with a count of elements. */
363 #ifdef CTOR_LIST_BEGIN
366 asm (CTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
367 STATIC func_ptr __CTOR_LIST__
[1] __attribute__ ((__unused__
))
368 = { (func_ptr
) (-1) };
371 #ifdef DTOR_LIST_BEGIN
374 asm (DTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
375 STATIC func_ptr __DTOR_LIST__
[1] = { (func_ptr
) (-1) };
378 #ifdef EH_FRAME_SECTION_ASM_OP
379 /* Stick a label at the beginning of the frame unwind info so we can register
380 and deregister it with the exception handling library code. */
382 asm (EH_FRAME_SECTION_ASM_OP
);
383 #ifdef INIT_SECTION_ASM_OP
386 char __EH_FRAME_BEGIN__
[] = { };
387 #endif /* EH_FRAME_SECTION_ASM_OP */
389 #endif /* defined(CRT_BEGIN) */
393 #ifdef INIT_SECTION_ASM_OP
395 #ifdef OBJECT_FORMAT_ELF
397 static func_ptr __CTOR_END__
[];
399 __do_global_ctors_aux (void)
402 for (p
= __CTOR_END__
- 1; *p
!= (func_ptr
) -1; p
--)
406 /* Stick a call to __do_global_ctors_aux into the .init section. */
408 static void __attribute__ ((__unused__
))
411 asm (INIT_SECTION_ASM_OP
);
412 CRT_CALL_STATIC_FUNCTION (__do_global_ctors_aux
);
413 #ifdef FORCE_INIT_SECTION_ALIGN
414 FORCE_INIT_SECTION_ALIGN
;
416 asm (TEXT_SECTION_ASM_OP
);
417 #ifdef CRT_END_INIT_DUMMY
422 #else /* OBJECT_FORMAT_ELF */
424 /* Stick the real initialization code, followed by a normal sort of
425 function epilogue at the very end of the .init section for this
426 entire root executable file or for this entire shared library file.
428 Note that we use some tricks here to get *just* the body and just
429 a function epilogue (but no function prologue) into the .init
430 section of the crtend.o file. Specifically, we switch to the .text
431 section, start to define a function, and then we switch to the .init
432 section just before the body code.
434 Earlier on, we put the corresponding function prologue into the .init
435 section of the crtbegin.o file (which will be linked in first).
437 Note that we want to invoke all constructors for C++ file-scope static-
438 storage objects AFTER any other possible initialization actions which
439 may be performed by the code in the .init section contributions made by
440 other libraries, etc. That's because those other initializations may
441 include setup operations for very primitive things (e.g. initializing
442 the state of the floating-point coprocessor, etc.) which should be done
443 before we start to execute any of the user's code. */
446 __do_global_ctors_aux (void) /* prologue goes in .text section */
448 asm (INIT_SECTION_ASM_OP
);
449 DO_GLOBAL_CTORS_BODY
;
450 atexit (__do_global_dtors
);
451 } /* epilogue and body go in .init section */
453 #ifdef FORCE_INIT_SECTION_ALIGN
454 FORCE_INIT_SECTION_ALIGN
;
457 asm (TEXT_SECTION_ASM_OP
);
459 #endif /* OBJECT_FORMAT_ELF */
461 #else /* defined(INIT_SECTION_ASM_OP) */
463 #ifdef HAS_INIT_SECTION
464 /* This case is used by the Irix 6 port, which supports named sections but
465 not an SVR4-style .init section. __do_global_ctors can be non-static
466 in this case because we protect it with -hidden_symbol. */
467 static func_ptr __CTOR_END__
[];
468 #ifdef EH_FRAME_SECTION_ASM_OP
469 extern void __frame_dummy (void);
472 __do_global_ctors (void)
475 #ifdef EH_FRAME_SECTION_ASM_OP
478 for (p
= __CTOR_END__
- 1; *p
!= (func_ptr
) -1; p
--)
483 #endif /* defined(INIT_SECTION_ASM_OP) */
485 /* Force cc1 to switch to .data section. */
486 static func_ptr force_to_data
[1] __attribute__ ((__unused__
)) = { };
488 /* Put a word containing zero at the end of each of our two lists of function
489 addresses. Note that the words defined here go into the .ctors and .dtors
490 sections of the crtend.o file, and since that file is always linked in
491 last, these words naturally end up at the very ends of the two lists
492 contained in these two sections. */
497 asm (CTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
498 STATIC func_ptr __CTOR_END__
[1] = { (func_ptr
) 0 };
504 asm (DTORS_SECTION_ASM_OP
); /* cc1 doesn't know that we are switching! */
505 STATIC func_ptr __DTOR_END__
[1] __attribute__ ((__unused__
))
509 #ifdef EH_FRAME_SECTION_ASM_OP
510 /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
511 this would be the 'length' field in a real FDE. */
513 typedef unsigned int ui32
__attribute__ ((mode (SI
)));
514 asm (EH_FRAME_SECTION_ASM_OP
);
515 STATIC ui32 __FRAME_END__
[] __attribute__ ((__unused__
)) = { 0 };
516 #endif /* EH_FRAME_SECTION */
518 #endif /* defined(CRT_END) */
520 #else /* OBJECT_FORMAT_MACHO */
522 /* For Mach-O format executables, we assume that the system's runtime is
523 smart enough to handle constructors and destructors, but doesn't have
524 an init section (if it can't even handle constructors/destructors
525 you should be using INVOKE__main, not crtstuff). All we need to do
526 is install/deinstall the frame information for exceptions. We do this
527 by putting a constructor in crtbegin.o and a destructor in crtend.o.
529 crtend.o also puts in the terminating zero in the frame information
532 /* The crtstuff for other object formats use the symbol __EH_FRAME_BEGIN__
533 to figure out the start of the exception frame, but here we use
534 getsectbynamefromheader to find this value. Either method would work,
535 but this method avoids creating any global symbols, which seems
538 #include <mach-o/ldsyms.h>
539 extern const struct section
*
540 getsectbynamefromheader (const struct mach_header
*,
541 const char *, const char *);
545 static void __reg_frame_ctor (void) __attribute__ ((constructor
));
548 __reg_frame_ctor (void)
550 static struct object object
;
551 const struct section
*eh_frame
;
553 eh_frame
= getsectbynamefromheader (&_mh_execute_header
,
554 "__TEXT", "__eh_frame");
555 __register_frame_info ((void *) eh_frame
->addr
, &object
);
558 #endif /* CRT_BEGIN */
562 static void __dereg_frame_dtor (void) __attribute__ ((destructor
));
565 __dereg_frame_dtor (void)
567 const struct section
*eh_frame
;
569 eh_frame
= getsectbynamefromheader (&_mh_execute_header
,
570 "__TEXT", "__eh_frame");
571 __deregister_frame_info ((void *) eh_frame
->addr
);
574 /* Terminate the frame section with a final zero. */
576 /* Force cc1 to switch to .data section. */
577 static void * force_to_data
[1] __attribute__ ((__unused__
)) = { };
579 typedef unsigned int ui32
__attribute__ ((mode (SI
)));
580 asm (EH_FRAME_SECTION_ASM_OP
);
581 static ui32 __FRAME_END__
[] __attribute__ ((__unused__
)) = { 0 };
585 #endif /* OBJECT_FORMAT_MACHO */