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 Free Software Foundation, Inc.
4 Contributed by Ron Guilmette (rfg@monkeys.com).
6 This file is part of GNU CC.
8 GNU CC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
13 GNU CC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GNU CC; see the file COPYING. If not, write to
20 the Free Software Foundation, 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
23 /* As a special exception, if you link this library with files
24 compiled with GCC to produce an executable, this does not cause
25 the resulting executable to be covered by the GNU General Public License.
26 This exception does not however invalidate any other reasons why
27 the executable file might be covered by the GNU General Public License. */
29 /* This file is a bit like libgcc1.c/libgcc2.c in that it is compiled
30 multiple times and yields multiple .o files.
32 This file is useful on target machines where the object file format
33 supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE). On
34 such systems, this file allows us to avoid running collect (or any
35 other such slow and painful kludge). Additionally, if the target
36 system supports a .init section, this file allows us to support the
37 linking of C++ code with a non-C++ main program.
39 Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then
40 this file *will* make use of the .init section. If that symbol is
41 not defined however, then the .init section will not be used.
43 Currently, only ELF and COFF are supported. It is likely however that
44 ROSE could also be supported, if someone was willing to do the work to
45 make whatever (small?) adaptations are needed. (Some work may be
46 needed on the ROSE assembler and linker also.)
48 This file must be compiled with gcc. */
50 /* It is incorrect to include config.h here, because this file is being
51 compiled for the target, and hence definitions concerning only the host
56 /* Provide default definitions for the pseudo-ops used to switch to the
57 .ctors and .dtors sections.
59 Note that we want to give these sections the SHF_WRITE attribute
60 because these sections will actually contain data (i.e. tables of
61 addresses of functions in the current root executable or shared library
62 file) and, in the case of a shared library, the relocatable addresses
63 will have to be properly resolved/relocated (and then written into) by
64 the dynamic linker when it actually attaches the given shared library
65 to the executing process. (Note that on SVR4, you may wish to use the
66 `-z text' option to the ELF linker, when building a shared library, as
67 an additional check that you are doing everything right. But if you do
68 use the `-z text' option when building a shared library, you will get
69 errors unless the .ctors and .dtors sections are marked as writable
70 via the SHF_WRITE attribute.) */
72 #ifndef CTORS_SECTION_ASM_OP
73 #define CTORS_SECTION_ASM_OP ".section\t.ctors,\"aw\""
75 #ifndef DTORS_SECTION_ASM_OP
76 #define DTORS_SECTION_ASM_OP ".section\t.dtors,\"aw\""
79 #ifdef OBJECT_FORMAT_ELF
81 /* Declare a pointer to void function type. */
82 typedef void (*func_ptr) (void);
85 #else /* OBJECT_FORMAT_ELF */
87 #include "gbl-ctors.h"
94 #endif /* OBJECT_FORMAT_ELF */
98 #ifdef INIT_SECTION_ASM_OP
100 #ifdef OBJECT_FORMAT_ELF
102 /* Run all the global destructors on exit from the program. */
104 /* Some systems place the number of pointers in the first word of the
105 table. On SVR4 however, that word is -1. In all cases, the table is
106 null-terminated. On SVR4, we start from the beginning of the list and
107 invoke each per-compilation-unit destructor routine in order
108 until we find that null.
110 Note that this function MUST be static. There will be one of these
111 functions in each root executable and one in each shared library, but
112 although they all have the same code, each one is unique in that it
113 refers to one particular associated `__DTOR_LIST__' which belongs to the
114 same particular root executable or shared library file. */
116 static func_ptr __DTOR_LIST__[];
118 __do_global_dtors_aux ()
121 for (p = __DTOR_LIST__ + 1; *p; p++)
125 /* Stick a call to __do_global_dtors_aux into the .fini section. */
130 asm (FINI_SECTION_ASM_OP);
131 __do_global_dtors_aux ();
132 #ifdef FORCE_FINI_SECTION_ALIGN
133 FORCE_FINI_SECTION_ALIGN;
135 asm (TEXT_SECTION_ASM_OP);
138 #else /* OBJECT_FORMAT_ELF */
140 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
141 and once in crtend.o). It must be declared static to avoid a link
142 error. Here, we define __do_global_ctors as an externally callable
143 function. It is externally callable so that __main can invoke it when
144 INVOKE__main is defined. This has the additional effect of forcing cc1
145 to switch to the .text section. */
147 static void __do_global_ctors_aux ();
148 void __do_global_ctors ()
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 ();
160 asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
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. */
168 #ifdef INIT_SECTION_PREAMBLE
169 INIT_SECTION_PREAMBLE;
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. */
178 __do_global_ctors_aux () /* prologue goes in .init section */
180 #ifdef FORCE_INIT_SECTION_ALIGN
181 FORCE_INIT_SECTION_ALIGN; /* Explicit align before switch to .text */
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);
188 #endif /* OBJECT_FORMAT_ELF */
189 #endif /* defined(INIT_SECTION_ASM_OP) */
191 /* Force cc1 to switch to .data section. */
192 static func_ptr force_to_data[0] = { };
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. */
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
211 asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
212 STATIC func_ptr __CTOR_LIST__[1] = { (func_ptr) (-1) };
215 #ifdef DTOR_LIST_BEGIN
218 asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
219 STATIC func_ptr __DTOR_LIST__[1] = { (func_ptr) (-1) };
222 #endif /* defined(CRT_BEGIN) */
226 #ifdef INIT_SECTION_ASM_OP
228 #ifdef OBJECT_FORMAT_ELF
230 static func_ptr __CTOR_END__[];
232 __do_global_ctors_aux ()
235 for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
239 /* Stick a call to __do_global_ctors_aux into the .init section. */
244 asm (INIT_SECTION_ASM_OP);
245 __do_global_ctors_aux ();
246 #ifdef FORCE_INIT_SECTION_ALIGN
247 FORCE_INIT_SECTION_ALIGN;
249 asm (TEXT_SECTION_ASM_OP);
251 /* This is a kludge. The i386 Linux dynamic linker needs ___brk_addr,
252 __environ and atexit (). We have to make sure they are in the .dynsym
253 section. We accomplish it by making a dummy call here. This
254 code is never reached. */
256 #if defined(__linux__) && defined(__PIC__) && defined(__i386__)
258 extern void *___brk_addr;
259 extern char **__environ;
261 ___brk_addr = __environ;
267 #else /* OBJECT_FORMAT_ELF */
269 /* Stick the real initialization code, followed by a normal sort of
270 function epilogue at the very end of the .init section for this
271 entire root executable file or for this entire shared library file.
273 Note that we use some tricks here to get *just* the body and just
274 a function epilogue (but no function prologue) into the .init
275 section of the crtend.o file. Specifically, we switch to the .text
276 section, start to define a function, and then we switch to the .init
277 section just before the body code.
279 Earlier on, we put the corresponding function prologue into the .init
280 section of the crtbegin.o file (which will be linked in first).
282 Note that we want to invoke all constructors for C++ file-scope static-
283 storage objects AFTER any other possible initialization actions which
284 may be performed by the code in the .init section contributions made by
285 other libraries, etc. That's because those other initializations may
286 include setup operations for very primitive things (e.g. initializing
287 the state of the floating-point coprocessor, etc.) which should be done
288 before we start to execute any of the user's code. */
291 __do_global_ctors_aux () /* prologue goes in .text section */
293 asm (INIT_SECTION_ASM_OP);
294 DO_GLOBAL_CTORS_BODY;
295 ON_EXIT (__do_global_dtors, 0);
296 } /* epilogue and body go in .init section */
298 #endif /* OBJECT_FORMAT_ELF */
300 #endif /* defined(INIT_SECTION_ASM_OP) */
302 /* Force cc1 to switch to .data section. */
303 static func_ptr force_to_data[0] = { };
305 /* Put a word containing zero at the end of each of our two lists of function
306 addresses. Note that the words defined here go into the .ctors and .dtors
307 sections of the crtend.o file, and since that file is always linked in
308 last, these words naturally end up at the very ends of the two lists
309 contained in these two sections. */
314 asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
315 STATIC func_ptr __CTOR_END__[1] = { (func_ptr) 0 };
321 asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */
322 STATIC func_ptr __DTOR_END__[1] = { (func_ptr) 0 };
325 #endif /* defined(CRT_END) */