crtstuff.c revision 18334
1/* Specialized bits of code needed to support construction and 2 destruction of file-scope objects in C++ code. 3 4 Written by Ron Guilmette (rfg@netcom.com) with help from Richard Stallman. 5 6Copyright (C) 1991, 1994, 1995 Free Software Foundation, Inc. 7 8This file is part of GNU CC. 9 10GNU CC is free software; you can redistribute it and/or modify 11it under the terms of the GNU General Public License as published by 12the Free Software Foundation; either version 2, or (at your option) 13any later version. 14 15GNU CC is distributed in the hope that it will be useful, 16but WITHOUT ANY WARRANTY; without even the implied warranty of 17MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18GNU General Public License for more details. 19 20You should have received a copy of the GNU General Public License 21along with GNU CC; see the file COPYING. If not, write to 22the Free Software Foundation, 59 Temple Place - Suite 330, 23Boston, MA 02111-1307, USA. */ 24 25/* As a special exception, if you link this library with files 26 compiled with GCC to produce an executable, this does not cause 27 the resulting executable to be covered by the GNU General Public License. 28 This exception does not however invalidate any other reasons why 29 the executable file might be covered by the GNU General Public License. */ 30 31/* This file is a bit like libgcc1.c/libgcc2.c in that it is compiled 32 multiple times and yields multiple .o files. 33 34 This file is useful on target machines where the object file format 35 supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE). On 36 such systems, this file allows us to avoid running collect (or any 37 other such slow and painful kludge). Additionally, if the target 38 system supports a .init section, this file allows us to support the 39 linking of C++ code with a non-C++ main program. 40 41 Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then 42 this file *will* make use of the .init section. If that symbol is 43 not defined however, then the .init section will not be used. 44 45 Currently, only ELF and COFF are supported. It is likely however that 46 ROSE could also be supported, if someone was willing to do the work to 47 make whatever (small?) adaptations are needed. (Some work may be 48 needed on the ROSE assembler and linker also.) 49 50 This file must be compiled with gcc. */ 51 52/* It is incorrect to include config.h here, because this file is being 53 compiled for the target, and hence definitions concerning only the host 54 do not apply. */ 55 56#include "tm.h" 57 58/* Provide default definitions for the pseudo-ops used to switch to the 59 .ctors and .dtors sections. 60 61 Note that we want to give these sections the SHF_WRITE attribute 62 because these sections will actually contain data (i.e. tables of 63 addresses of functions in the current root executable or shared library 64 file) and, in the case of a shared library, the relocatable addresses 65 will have to be properly resolved/relocated (and then written into) by 66 the dynamic linker when it actually attaches the given shared library 67 to the executing process. (Note that on SVR4, you may wish to use the 68 `-z text' option to the ELF linker, when building a shared library, as 69 an additional check that you are doing everything right. But if you do 70 use the `-z text' option when building a shared library, you will get 71 errors unless the .ctors and .dtors sections are marked as writable 72 via the SHF_WRITE attribute.) */ 73 74#ifndef CTORS_SECTION_ASM_OP 75#define CTORS_SECTION_ASM_OP ".section\t.ctors,\"aw\"" 76#endif 77#ifndef DTORS_SECTION_ASM_OP 78#define DTORS_SECTION_ASM_OP ".section\t.dtors,\"aw\"" 79#endif 80 81#ifdef OBJECT_FORMAT_ELF 82 83/* Declare a pointer to void function type. */ 84typedef void (*func_ptr) (void); 85#define STATIC static 86 87#else /* OBJECT_FORMAT_ELF */ 88 89#include "gbl-ctors.h" 90 91#ifndef ON_EXIT 92#define ON_EXIT(a, b) 93#endif 94#define STATIC 95 96#endif /* OBJECT_FORMAT_ELF */ 97 98#ifdef CRT_BEGIN 99 100#ifdef INIT_SECTION_ASM_OP 101 102#ifdef OBJECT_FORMAT_ELF 103 104/* Run all the global destructors on exit from the program. */ 105 106/* Some systems place the number of pointers in the first word of the 107 table. On SVR4 however, that word is -1. In all cases, the table is 108 null-terminated. On SVR4, we start from the beginning of the list and 109 invoke each per-compilation-unit destructor routine in order 110 until we find that null. 111 112 Note that this function MUST be static. There will be one of these 113 functions in each root executable and one in each shared library, but 114 although they all have the same code, each one is unique in that it 115 refers to one particular associated `__DTOR_LIST__' which belongs to the 116 same particular root executable or shared library file. */ 117 118static func_ptr __DTOR_LIST__[]; 119static void 120__do_global_dtors_aux () 121{ 122 func_ptr *p; 123 for (p = __DTOR_LIST__ + 1; *p; p++) 124 (*p) (); 125} 126 127/* Stick a call to __do_global_dtors_aux into the .fini section. */ 128static void 129fini_dummy () 130{ 131 asm (FINI_SECTION_ASM_OP); 132 __do_global_dtors_aux (); 133#ifdef FORCE_FINI_SECTION_ALIGN 134 FORCE_FINI_SECTION_ALIGN; 135#endif 136 asm (TEXT_SECTION_ASM_OP); 137} 138 139#else /* OBJECT_FORMAT_ELF */ 140 141/* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o 142 and once in crtend.o). It must be declared static to avoid a link 143 error. Here, we define __do_global_ctors as an externally callable 144 function. It is externally callable so that __main can invoke it when 145 INVOKE__main is defined. This has the additional effect of forcing cc1 146 to switch to the .text section. */ 147static void __do_global_ctors_aux (); 148void __do_global_ctors () 149{ 150#ifdef INVOKE__main /* If __main won't actually call __do_global_ctors 151 then it doesn't matter what's inside the function. 152 The inside of __do_global_ctors_aux is called 153 automatically in that case. 154 And the Alliant fx2800 linker crashes 155 on this reference. So prevent the crash. */ 156 __do_global_ctors_aux (); 157#endif 158} 159 160asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ 161 162/* On some svr4 systems, the initial .init section preamble code provided in 163 crti.o may do something, such as bump the stack, which we have to 164 undo before we reach the function prologue code for __do_global_ctors 165 (directly below). For such systems, define the macro INIT_SECTION_PREAMBLE 166 to expand into the code needed to undo the actions of the crti.o file. */ 167 168#ifdef INIT_SECTION_PREAMBLE 169 INIT_SECTION_PREAMBLE; 170#endif 171 172/* A routine to invoke all of the global constructors upon entry to the 173 program. We put this into the .init section (for systems that have 174 such a thing) so that we can properly perform the construction of 175 file-scope static-storage C++ objects within shared libraries. */ 176 177static void 178__do_global_ctors_aux () /* prologue goes in .init section */ 179{ 180#ifdef FORCE_INIT_SECTION_ALIGN 181 FORCE_INIT_SECTION_ALIGN; /* Explicit align before switch to .text */ 182#endif 183 asm (TEXT_SECTION_ASM_OP); /* don't put epilogue and body in .init */ 184 DO_GLOBAL_CTORS_BODY; 185 ON_EXIT (__do_global_dtors, 0); 186} 187 188#endif /* OBJECT_FORMAT_ELF */ 189#endif /* defined(INIT_SECTION_ASM_OP) */ 190 191/* Force cc1 to switch to .data section. */ 192static func_ptr force_to_data[0] = { }; 193 194/* NOTE: In order to be able to support SVR4 shared libraries, we arrange 195 to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__, 196 __DTOR_END__ } per root executable and also one set of these symbols 197 per shared library. So in any given whole process image, we may have 198 multiple definitions of each of these symbols. In order to prevent 199 these definitions from conflicting with one another, and in order to 200 ensure that the proper lists are used for the initialization/finalization 201 of each individual shared library (respectively), we give these symbols 202 only internal (i.e. `static') linkage, and we also make it a point to 203 refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__ 204 symbol in crtbegin.o, where they are defined. */ 205 206/* The -1 is a flag to __do_global_[cd]tors 207 indicating that this table does not start with a count of elements. */ 208#ifdef CTOR_LIST_BEGIN 209CTOR_LIST_BEGIN; 210#else 211asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ 212STATIC func_ptr __CTOR_LIST__[1] = { (func_ptr) (-1) }; 213#endif 214 215#ifdef DTOR_LIST_BEGIN 216DTOR_LIST_BEGIN; 217#else 218asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ 219STATIC func_ptr __DTOR_LIST__[1] = { (func_ptr) (-1) }; 220#endif 221 222#endif /* defined(CRT_BEGIN) */ 223 224#ifdef CRT_END 225 226#ifdef INIT_SECTION_ASM_OP 227 228#ifdef OBJECT_FORMAT_ELF 229 230static func_ptr __CTOR_END__[]; 231static void 232__do_global_ctors_aux () 233{ 234 func_ptr *p; 235 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--) 236 (*p) (); 237} 238 239/* Stick a call to __do_global_ctors_aux into the .init section. */ 240static void 241init_dummy () 242{ 243 asm (INIT_SECTION_ASM_OP); 244 __do_global_ctors_aux (); 245#ifdef FORCE_INIT_SECTION_ALIGN 246 FORCE_INIT_SECTION_ALIGN; 247#endif 248 asm (TEXT_SECTION_ASM_OP); 249 250/* This is a kludge. The Linux dynamic linker needs ___brk_addr, __environ 251 and atexit (). We have to make sure they are in the .dynsym section. We 252 accomplish it by making a dummy call here. This 253 code is never reached. */ 254 255#if defined(__linux__) && defined(__PIC__) 256 { 257 extern void *___brk_addr; 258 extern char **__environ; 259 260 ___brk_addr = __environ; 261 atexit (); 262 } 263#endif 264} 265 266#else /* OBJECT_FORMAT_ELF */ 267 268/* Stick the real initialization code, followed by a normal sort of 269 function epilogue at the very end of the .init section for this 270 entire root executable file or for this entire shared library file. 271 272 Note that we use some tricks here to get *just* the body and just 273 a function epilogue (but no function prologue) into the .init 274 section of the crtend.o file. Specifically, we switch to the .text 275 section, start to define a function, and then we switch to the .init 276 section just before the body code. 277 278 Earlier on, we put the corresponding function prologue into the .init 279 section of the crtbegin.o file (which will be linked in first). 280 281 Note that we want to invoke all constructors for C++ file-scope static- 282 storage objects AFTER any other possible initialization actions which 283 may be performed by the code in the .init section contributions made by 284 other libraries, etc. That's because those other initializations may 285 include setup operations for very primitive things (e.g. initializing 286 the state of the floating-point coprocessor, etc.) which should be done 287 before we start to execute any of the user's code. */ 288 289static void 290__do_global_ctors_aux () /* prologue goes in .text section */ 291{ 292 asm (INIT_SECTION_ASM_OP); 293 DO_GLOBAL_CTORS_BODY; 294 ON_EXIT (__do_global_dtors, 0); 295} /* epilogue and body go in .init section */ 296 297#endif /* OBJECT_FORMAT_ELF */ 298 299#endif /* defined(INIT_SECTION_ASM_OP) */ 300 301/* Force cc1 to switch to .data section. */ 302static func_ptr force_to_data[0] = { }; 303 304/* Put a word containing zero at the end of each of our two lists of function 305 addresses. Note that the words defined here go into the .ctors and .dtors 306 sections of the crtend.o file, and since that file is always linked in 307 last, these words naturally end up at the very ends of the two lists 308 contained in these two sections. */ 309 310#ifdef CTOR_LIST_END 311CTOR_LIST_END; 312#else 313asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ 314STATIC func_ptr __CTOR_END__[1] = { (func_ptr) 0 }; 315#endif 316 317#ifdef DTOR_LIST_END 318DTOR_LIST_END; 319#else 320asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ 321STATIC func_ptr __DTOR_END__[1] = { (func_ptr) 0 }; 322#endif 323 324#endif /* defined(CRT_END) */ 325