crtstuff.c revision 117395
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, 2002 Free Software Foundation, Inc. 5 Contributed by Ron Guilmette (rfg@monkeys.com). 6 7This file is part of GCC. 8 9GCC is free software; you can redistribute it and/or modify it under 10the terms of the GNU General Public License as published by the Free 11Software Foundation; either version 2, or (at your option) any later 12version. 13 14In addition to the permissions in the GNU General Public License, the 15Free Software Foundation gives you unlimited permission to link the 16compiled version of this file into combinations with other programs, 17and to distribute those combinations without any restriction coming 18from the use of this file. (The General Public License restrictions 19do apply in other respects; for example, they cover modification of 20the file, and distribution when not linked into a combine 21executable.) 22 23GCC is distributed in the hope that it will be useful, but WITHOUT ANY 24WARRANTY; without even the implied warranty of MERCHANTABILITY or 25FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 26for more details. 27 28You should have received a copy of the GNU General Public License 29along with GCC; see the file COPYING. If not, write to the Free 30Software Foundation, 59 Temple Place - Suite 330, Boston, MA 3102111-1307, USA. */ 32 33/* This file is a bit like libgcc2.c in that it is compiled 34 multiple times and yields multiple .o files. 35 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. 42 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. 46 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.) 51 52 This file must be compiled with gcc. */ 53 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 56 do not apply. */ 57 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" 61#include "tconfig.h" 62#include "tsystem.h" 63#include "unwind-dw2-fde.h" 64 65#ifndef FORCE_CODE_SECTION_ALIGN 66# define FORCE_CODE_SECTION_ALIGN 67#endif 68 69#ifndef CRT_CALL_STATIC_FUNCTION 70# define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC) \ 71static void __attribute__((__used__)) \ 72call_ ## FUNC (void) \ 73{ \ 74 asm (SECTION_OP); \ 75 FUNC (); \ 76 FORCE_CODE_SECTION_ALIGN \ 77 asm (TEXT_SECTION_ASM_OP); \ 78} 79#endif 80 81#if defined(OBJECT_FORMAT_ELF) && defined(HAVE_LD_EH_FRAME_HDR) \ 82 && !defined(inhibit_libc) && !defined(CRTSTUFFT_O) \ 83 && defined(__GLIBC__) && __GLIBC__ >= 2 84#include <link.h> 85# if (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \ 86 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG))) 87# define USE_PT_GNU_EH_FRAME 88# endif 89#endif 90#if defined(EH_FRAME_SECTION_NAME) && !defined(USE_PT_GNU_EH_FRAME) 91# define USE_EH_FRAME_REGISTRY 92#endif 93#if defined(EH_FRAME_SECTION_NAME) && defined(HAVE_LD_RO_RW_SECTION_MIXING) 94# define EH_FRAME_SECTION_CONST const 95#else 96# define EH_FRAME_SECTION_CONST 97#endif 98 99/* We do not want to add the weak attribute to the declarations of these 100 routines in unwind-dw2-fde.h because that will cause the definition of 101 these symbols to be weak as well. 102 103 This exposes a core issue, how to handle creating weak references vs 104 how to create weak definitions. Either we have to have the definition 105 of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or 106 have a second declaration if we want a function's references to be weak, 107 but not its definition. 108 109 Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until 110 one thinks about scaling to larger problems -- ie, the condition under 111 which TARGET_WEAK_ATTRIBUTE is active will eventually get far too 112 complicated. 113 114 So, we take an approach similar to #pragma weak -- we have a second 115 declaration for functions that we want to have weak references. 116 117 Neither way is particularly good. */ 118 119/* References to __register_frame_info and __deregister_frame_info should 120 be weak in this file if at all possible. */ 121extern void __register_frame_info (void *, struct object *) 122 TARGET_ATTRIBUTE_WEAK; 123extern void __register_frame_info_bases (void *, struct object *, 124 void *, void *) 125 TARGET_ATTRIBUTE_WEAK; 126extern void *__deregister_frame_info (void *) 127 TARGET_ATTRIBUTE_WEAK; 128extern void *__deregister_frame_info_bases (void *) 129 TARGET_ATTRIBUTE_WEAK; 130 131/* Likewise for _Jv_RegisterClasses. */ 132extern void _Jv_RegisterClasses (void *) TARGET_ATTRIBUTE_WEAK; 133 134#ifdef OBJECT_FORMAT_ELF 135 136/* Declare a pointer to void function type. */ 137typedef void (*func_ptr) (void); 138#define STATIC static 139 140#else /* OBJECT_FORMAT_ELF */ 141 142#include "gbl-ctors.h" 143 144#define STATIC 145 146#endif /* OBJECT_FORMAT_ELF */ 147 148#ifdef CRT_BEGIN 149 150/* NOTE: In order to be able to support SVR4 shared libraries, we arrange 151 to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__, 152 __DTOR_END__ } per root executable and also one set of these symbols 153 per shared library. So in any given whole process image, we may have 154 multiple definitions of each of these symbols. In order to prevent 155 these definitions from conflicting with one another, and in order to 156 ensure that the proper lists are used for the initialization/finalization 157 of each individual shared library (respectively), we give these symbols 158 only internal (i.e. `static') linkage, and we also make it a point to 159 refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__ 160 symbol in crtbegin.o, where they are defined. */ 161 162/* The -1 is a flag to __do_global_[cd]tors indicating that this table 163 does not start with a count of elements. */ 164#ifdef CTOR_LIST_BEGIN 165CTOR_LIST_BEGIN; 166#elif defined(CTORS_SECTION_ASM_OP) 167/* Hack: force cc1 to switch to .data section early, so that assembling 168 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */ 169static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { }; 170asm (CTORS_SECTION_ASM_OP); 171STATIC func_ptr __CTOR_LIST__[1] 172 __attribute__ ((__unused__, aligned(sizeof(func_ptr)))) 173 = { (func_ptr) (-1) }; 174#else 175STATIC func_ptr __CTOR_LIST__[1] 176 __attribute__ ((__unused__, section(".ctors"), aligned(sizeof(func_ptr)))) 177 = { (func_ptr) (-1) }; 178#endif /* __CTOR_LIST__ alternatives */ 179 180#ifdef DTOR_LIST_BEGIN 181DTOR_LIST_BEGIN; 182#elif defined(DTORS_SECTION_ASM_OP) 183asm (DTORS_SECTION_ASM_OP); 184STATIC func_ptr __DTOR_LIST__[1] 185 __attribute__ ((aligned(sizeof(func_ptr)))) 186 = { (func_ptr) (-1) }; 187#else 188STATIC func_ptr __DTOR_LIST__[1] 189 __attribute__((section(".dtors"), aligned(sizeof(func_ptr)))) 190 = { (func_ptr) (-1) }; 191#endif /* __DTOR_LIST__ alternatives */ 192 193#ifdef USE_EH_FRAME_REGISTRY 194/* Stick a label at the beginning of the frame unwind info so we can register 195 and deregister it with the exception handling library code. */ 196STATIC EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[] 197 __attribute__((section(EH_FRAME_SECTION_NAME), aligned(4))) 198 = { }; 199#endif /* USE_EH_FRAME_REGISTRY */ 200 201#ifdef JCR_SECTION_NAME 202/* Stick a label at the beginning of the java class registration info 203 so we can register them properly. */ 204STATIC void *__JCR_LIST__[] 205 __attribute__ ((unused, section(JCR_SECTION_NAME), aligned(sizeof(void*)))) 206 = { }; 207#endif /* JCR_SECTION_NAME */ 208 209#ifdef INIT_SECTION_ASM_OP 210 211#ifdef OBJECT_FORMAT_ELF 212 213/* Declare the __dso_handle variable. It should have a unique value 214 in every shared-object; in a main program its value is zero. The 215 object should in any case be protected. This means the instance 216 in one DSO or the main program is not used in another object. The 217 dynamic linker takes care of this. */ 218 219#ifdef HAVE_GAS_HIDDEN 220extern void *__dso_handle __attribute__ ((__visibility__ ("hidden"))); 221#endif 222#ifdef CRTSTUFFS_O 223void *__dso_handle = &__dso_handle; 224#else 225void *__dso_handle = 0; 226#endif 227 228/* The __cxa_finalize function may not be available so we use only a 229 weak declaration. */ 230extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK; 231 232/* Run all the global destructors on exit from the program. */ 233 234/* Some systems place the number of pointers in the first word of the 235 table. On SVR4 however, that word is -1. In all cases, the table is 236 null-terminated. On SVR4, we start from the beginning of the list and 237 invoke each per-compilation-unit destructor routine in order 238 until we find that null. 239 240 Note that this function MUST be static. There will be one of these 241 functions in each root executable and one in each shared library, but 242 although they all have the same code, each one is unique in that it 243 refers to one particular associated `__DTOR_LIST__' which belongs to the 244 same particular root executable or shared library file. 245 246 On some systems, this routine is run more than once from the .fini, 247 when exit is called recursively, so we arrange to remember where in 248 the list we left off processing, and we resume at that point, 249 should we be re-invoked. */ 250 251static void __attribute__((used)) 252__do_global_dtors_aux (void) 253{ 254 static func_ptr *p = __DTOR_LIST__ + 1; 255 static _Bool completed; 256 func_ptr f; 257 258 if (__builtin_expect (completed, 0)) 259 return; 260 261#ifdef CRTSTUFFS_O 262 if (__cxa_finalize) 263 __cxa_finalize (__dso_handle); 264#endif 265 266 while ((f = *p)) 267 { 268 p++; 269 f (); 270 } 271 272#ifdef USE_EH_FRAME_REGISTRY 273#if defined(CRT_GET_RFIB_TEXT) || defined(CRT_GET_RFIB_DATA) 274 /* If we used the new __register_frame_info_bases interface, 275 make sure that we deregister from the same place. */ 276 if (__deregister_frame_info_bases) 277 __deregister_frame_info_bases (__EH_FRAME_BEGIN__); 278#else 279 if (__deregister_frame_info) 280 __deregister_frame_info (__EH_FRAME_BEGIN__); 281#endif 282#endif 283 284 completed = 1; 285} 286 287/* Stick a call to __do_global_dtors_aux into the .fini section. */ 288CRT_CALL_STATIC_FUNCTION (FINI_SECTION_ASM_OP, __do_global_dtors_aux) 289 290#if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME) 291/* Stick a call to __register_frame_info into the .init section. For some 292 reason calls with no arguments work more reliably in .init, so stick the 293 call in another function. */ 294 295static void __attribute__((used)) 296frame_dummy (void) 297{ 298#ifdef USE_EH_FRAME_REGISTRY 299 static struct object object; 300#if defined(CRT_GET_RFIB_TEXT) || defined(CRT_GET_RFIB_DATA) 301 void *tbase, *dbase; 302#ifdef CRT_GET_RFIB_TEXT 303 CRT_GET_RFIB_TEXT (tbase); 304#else 305 tbase = 0; 306#endif 307#ifdef CRT_GET_RFIB_DATA 308 CRT_GET_RFIB_DATA (dbase); 309#else 310 dbase = 0; 311#endif 312 if (__register_frame_info_bases) 313 __register_frame_info_bases (__EH_FRAME_BEGIN__, &object, tbase, dbase); 314#else 315 if (__register_frame_info) 316 __register_frame_info (__EH_FRAME_BEGIN__, &object); 317#endif 318#endif /* USE_EH_FRAME_REGISTRY */ 319#ifdef JCR_SECTION_NAME 320 if (__JCR_LIST__[0] && _Jv_RegisterClasses) 321 _Jv_RegisterClasses (__JCR_LIST__); 322#endif /* JCR_SECTION_NAME */ 323} 324 325CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, frame_dummy) 326#endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */ 327 328#else /* OBJECT_FORMAT_ELF */ 329 330/* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o 331 and once in crtend.o). It must be declared static to avoid a link 332 error. Here, we define __do_global_ctors as an externally callable 333 function. It is externally callable so that __main can invoke it when 334 INVOKE__main is defined. This has the additional effect of forcing cc1 335 to switch to the .text section. */ 336 337static void __do_global_ctors_aux (void); 338void 339__do_global_ctors (void) 340{ 341#ifdef INVOKE__main 342 /* If __main won't actually call __do_global_ctors then it doesn't matter 343 what's inside the function. The inside of __do_global_ctors_aux is 344 called automatically in that case. And the Alliant fx2800 linker 345 crashes on this reference. So prevent the crash. */ 346 __do_global_ctors_aux (); 347#endif 348} 349 350asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ 351 352/* On some svr4 systems, the initial .init section preamble code provided in 353 crti.o may do something, such as bump the stack, which we have to 354 undo before we reach the function prologue code for __do_global_ctors 355 (directly below). For such systems, define the macro INIT_SECTION_PREAMBLE 356 to expand into the code needed to undo the actions of the crti.o file. */ 357 358#ifdef INIT_SECTION_PREAMBLE 359 INIT_SECTION_PREAMBLE; 360#endif 361 362/* A routine to invoke all of the global constructors upon entry to the 363 program. We put this into the .init section (for systems that have 364 such a thing) so that we can properly perform the construction of 365 file-scope static-storage C++ objects within shared libraries. */ 366 367static void __attribute__((used)) 368__do_global_ctors_aux (void) /* prologue goes in .init section */ 369{ 370 FORCE_CODE_SECTION_ALIGN /* explicit align before switch to .text */ 371 asm (TEXT_SECTION_ASM_OP); /* don't put epilogue and body in .init */ 372 DO_GLOBAL_CTORS_BODY; 373 atexit (__do_global_dtors); 374} 375 376#endif /* OBJECT_FORMAT_ELF */ 377 378#elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */ 379 380/* This case is used by the Irix 6 port, which supports named sections but 381 not an SVR4-style .fini section. __do_global_dtors can be non-static 382 in this case because we protect it with -hidden_symbol. */ 383 384void 385__do_global_dtors (void) 386{ 387 func_ptr *p, f; 388 for (p = __DTOR_LIST__ + 1; (f = *p); p++) 389 f (); 390 391#ifdef USE_EH_FRAME_REGISTRY 392 if (__deregister_frame_info) 393 __deregister_frame_info (__EH_FRAME_BEGIN__); 394#endif 395} 396 397#if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME) 398/* A helper function for __do_global_ctors, which is in crtend.o. Here 399 in crtbegin.o, we can reference a couple of symbols not visible there. 400 Plus, since we're before libgcc.a, we have no problems referencing 401 functions from there. */ 402void 403__do_global_ctors_1(void) 404{ 405#ifdef USE_EH_FRAME_REGISTRY 406 static struct object object; 407 if (__register_frame_info) 408 __register_frame_info (__EH_FRAME_BEGIN__, &object); 409#endif 410#ifdef JCR_SECTION_NAME 411 if (__JCR_LIST__[0] && _Jv_RegisterClasses) 412 _Jv_RegisterClasses (__JCR_LIST__); 413#endif 414} 415#endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */ 416 417#else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */ 418#error "What are you doing with crtstuff.c, then?" 419#endif 420 421#elif defined(CRT_END) /* ! CRT_BEGIN */ 422 423/* Put a word containing zero at the end of each of our two lists of function 424 addresses. Note that the words defined here go into the .ctors and .dtors 425 sections of the crtend.o file, and since that file is always linked in 426 last, these words naturally end up at the very ends of the two lists 427 contained in these two sections. */ 428 429#ifdef CTOR_LIST_END 430CTOR_LIST_END; 431#elif defined(CTORS_SECTION_ASM_OP) 432/* Hack: force cc1 to switch to .data section early, so that assembling 433 __CTOR_LIST__ does not undo our behind-the-back change to .ctors. */ 434static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { }; 435asm (CTORS_SECTION_ASM_OP); 436STATIC func_ptr __CTOR_END__[1] 437 __attribute__((aligned(sizeof(func_ptr)))) 438 = { (func_ptr) 0 }; 439#else 440STATIC func_ptr __CTOR_END__[1] 441 __attribute__((section(".ctors"), aligned(sizeof(func_ptr)))) 442 = { (func_ptr) 0 }; 443#endif 444 445#ifdef DTOR_LIST_END 446DTOR_LIST_END; 447#elif defined(DTORS_SECTION_ASM_OP) 448asm (DTORS_SECTION_ASM_OP); 449STATIC func_ptr __DTOR_END__[1] 450 __attribute__ ((unused, aligned(sizeof(func_ptr)))) 451 = { (func_ptr) 0 }; 452#else 453STATIC func_ptr __DTOR_END__[1] 454 __attribute__((unused, section(".dtors"), aligned(sizeof(func_ptr)))) 455 = { (func_ptr) 0 }; 456#endif 457 458#ifdef EH_FRAME_SECTION_NAME 459/* Terminate the frame unwind info section with a 4byte 0 as a sentinel; 460 this would be the 'length' field in a real FDE. */ 461STATIC EH_FRAME_SECTION_CONST int __FRAME_END__[] 462 __attribute__ ((unused, mode(SI), section(EH_FRAME_SECTION_NAME), 463 aligned(4))) 464 = { 0 }; 465#endif /* EH_FRAME_SECTION_NAME */ 466 467#ifdef JCR_SECTION_NAME 468/* Null terminate the .jcr section array. */ 469STATIC void *__JCR_END__[1] 470 __attribute__ ((unused, section(JCR_SECTION_NAME), 471 aligned(sizeof(void *)))) 472 = { 0 }; 473#endif /* JCR_SECTION_NAME */ 474 475#ifdef INIT_SECTION_ASM_OP 476 477#ifdef OBJECT_FORMAT_ELF 478static void __attribute__((used)) 479__do_global_ctors_aux (void) 480{ 481 func_ptr *p; 482 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--) 483 (*p) (); 484} 485 486/* Stick a call to __do_global_ctors_aux into the .init section. */ 487CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, __do_global_ctors_aux) 488#else /* OBJECT_FORMAT_ELF */ 489 490/* Stick the real initialization code, followed by a normal sort of 491 function epilogue at the very end of the .init section for this 492 entire root executable file or for this entire shared library file. 493 494 Note that we use some tricks here to get *just* the body and just 495 a function epilogue (but no function prologue) into the .init 496 section of the crtend.o file. Specifically, we switch to the .text 497 section, start to define a function, and then we switch to the .init 498 section just before the body code. 499 500 Earlier on, we put the corresponding function prologue into the .init 501 section of the crtbegin.o file (which will be linked in first). 502 503 Note that we want to invoke all constructors for C++ file-scope static- 504 storage objects AFTER any other possible initialization actions which 505 may be performed by the code in the .init section contributions made by 506 other libraries, etc. That's because those other initializations may 507 include setup operations for very primitive things (e.g. initializing 508 the state of the floating-point coprocessor, etc.) which should be done 509 before we start to execute any of the user's code. */ 510 511static void 512__do_global_ctors_aux (void) /* prologue goes in .text section */ 513{ 514 asm (INIT_SECTION_ASM_OP); 515 DO_GLOBAL_CTORS_BODY; 516 atexit (__do_global_dtors); 517} /* epilogue and body go in .init section */ 518 519FORCE_CODE_SECTION_ALIGN 520asm (TEXT_SECTION_ASM_OP); 521 522#endif /* OBJECT_FORMAT_ELF */ 523 524#elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */ 525 526/* This case is used by the Irix 6 port, which supports named sections but 527 not an SVR4-style .init section. __do_global_ctors can be non-static 528 in this case because we protect it with -hidden_symbol. */ 529extern void __do_global_ctors_1(void); 530void 531__do_global_ctors (void) 532{ 533 func_ptr *p; 534#if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME) 535 __do_global_ctors_1(); 536#endif 537 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--) 538 (*p) (); 539} 540 541#else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */ 542#error "What are you doing with crtstuff.c, then?" 543#endif 544 545#else /* ! CRT_BEGIN && ! CRT_END */ 546#error "One of CRT_BEGIN or CRT_END must be defined." 547#endif 548