gcc/config/alpha/elf.h

   1 /* Definitions of target machine for GNU compiler, for DEC Alpha w/ELF.
   2    Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002
   3    Free Software Foundation, Inc.
   4    Contributed by Richard Henderson (rth@tamu.edu).
   5
   6 This file is part of GNU CC.
   7
   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)
  11 any later version.
  12
  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.
  17
  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.    */
  22
  23 #undef OBJECT_FORMAT_COFF
  24 #undef EXTENDED_COFF
  25 #define OBJECT_FORMAT_ELF
  26
  27 /* ??? Move all SDB stuff from alpha.h to osf.h.  */
  28 #undef SDB_DEBUGGING_INFO
  29
  30 #define DBX_DEBUGGING_INFO 1
  31 #define DWARF2_DEBUGGING_INFO 1
  32
  33 #undef  PREFERRED_DEBUGGING_TYPE
  34 #define PREFERRED_DEBUGGING_TYPE DWARF2_DEBUG
  35
  36 #undef ASM_FINAL_SPEC
  37
  38 #undef  CPP_SUBTARGET_SPEC
  39 #define CPP_SUBTARGET_SPEC "-D__ELF__"
  40
  41 #undef  CC1_SPEC
  42 #define CC1_SPEC  "%{G*}"
  43
  44 #undef  ASM_SPEC
  45 #define ASM_SPEC  "%{G*} %{relax:-relax} %{!gstabs*:-no-mdebug}%{gstabs*:-mdebug}"
  46
  47 /* Output at beginning of assembler file.  */
  48 #undef  ASM_FILE_START
  49 #define ASM_FILE_START(FILE)                                    \
  50 do {                                                            \
  51   if (write_symbols == DBX_DEBUG)                               \
  52     {                                                           \
  53       alpha_write_verstamp (FILE);                              \
  54       output_file_directive (FILE, main_input_filename);        \
  55     }                                                           \
  56   fprintf (FILE, "\t.set noat\n");                              \
  57   fprintf (FILE, "\t.set noreorder\n");                         \
  58   if (TARGET_EXPLICIT_RELOCS)                                   \
  59     fprintf (FILE, "\t.set nomacro\n");                         \
  60   if (TARGET_BWX | TARGET_MAX | TARGET_FIX | TARGET_CIX)        \
  61     {                                                           \
  62       fprintf (FILE, "\t.arch %s\n",                            \
  63                (TARGET_CPU_EV6 ? "ev6"                          \
  64                 : TARGET_MAX ? "pca56" : "ev56"));              \
  65     }                                                           \
  66 } while (0)
  67
  68 #undef  IDENT_ASM_OP
  69 #define IDENT_ASM_OP "\t.ident\t"
  70
  71 /* Output #ident as a .ident.  */
  72 #undef  ASM_OUTPUT_IDENT
  73 #define ASM_OUTPUT_IDENT(FILE, NAME) \
  74   fprintf (FILE, "%s\"%s\"\n", IDENT_ASM_OP, NAME);
  75
  76 /* This is how to allocate empty space in some section.  The .zero
  77    pseudo-op is used for this on most svr4 assemblers.  */
  78
  79 #undef  SKIP_ASM_OP
  80 #define SKIP_ASM_OP     "\t.zero\t"
  81
  82 #undef  ASM_OUTPUT_SKIP
  83 #define ASM_OUTPUT_SKIP(FILE, SIZE) \
  84   fprintf (FILE, "%s%u\n", SKIP_ASM_OP, (SIZE))
  85
  86 /* Output the label which precedes a jumptable.  Note that for all svr4
  87    systems where we actually generate jumptables (which is to say every
  88    svr4 target except i386, where we use casesi instead) we put the jump-
  89    tables into the .rodata section and since other stuff could have been
  90    put into the .rodata section prior to any given jumptable, we have to
  91    make sure that the location counter for the .rodata section gets pro-
  92    perly re-aligned prior to the actual beginning of the jump table.  */
  93
  94 #undef  ALIGN_ASM_OP
  95 #define ALIGN_ASM_OP "\t.align\t"
  96
  97 #ifndef ASM_OUTPUT_BEFORE_CASE_LABEL
  98 #define ASM_OUTPUT_BEFORE_CASE_LABEL(FILE, PREFIX, NUM, TABLE) \
  99   ASM_OUTPUT_ALIGN ((FILE), 2);
 100 #endif
 101
 102 #undef  ASM_OUTPUT_CASE_LABEL
 103 #define ASM_OUTPUT_CASE_LABEL(FILE, PREFIX, NUM, JUMPTABLE)             \
 104   do {                                                                  \
 105     ASM_OUTPUT_BEFORE_CASE_LABEL (FILE, PREFIX, NUM, JUMPTABLE)         \
 106     (*targetm.asm_out.internal_label) (FILE, PREFIX, NUM);                      \
 107   } while (0)
 108
 109 /* The standard SVR4 assembler seems to require that certain builtin
 110    library routines (e.g. .udiv) be explicitly declared as .globl
 111    in each assembly file where they are referenced.  */
 112
 113 #undef  ASM_OUTPUT_EXTERNAL_LIBCALL
 114 #define ASM_OUTPUT_EXTERNAL_LIBCALL(FILE, FUN)                          \
 115   (*targetm.asm_out.globalize_label) (FILE, XSTR (FUN, 0))
 116
 117 /* This says how to output assembler code to declare an
 118    uninitialized external linkage data object.  Under SVR4,
 119    the linker seems to want the alignment of data objects
 120    to depend on their types.  We do exactly that here.  */
 121
 122 #undef  COMMON_ASM_OP
 123 #define COMMON_ASM_OP   "\t.comm\t"
 124
 125 #undef  ASM_OUTPUT_ALIGNED_COMMON
 126 #define ASM_OUTPUT_ALIGNED_COMMON(FILE, NAME, SIZE, ALIGN)              \
 127 do {                                                                    \
 128   fprintf ((FILE), "%s", COMMON_ASM_OP);                                \
 129   assemble_name ((FILE), (NAME));                                       \
 130   fprintf ((FILE), ",%u,%u\n", (SIZE), (ALIGN) / BITS_PER_UNIT);        \
 131 } while (0)
 132
 133 /* This says how to output assembler code to declare an
 134    uninitialized internal linkage data object.  Under SVR4,
 135    the linker seems to want the alignment of data objects
 136    to depend on their types.  We do exactly that here.  */
 137
 138 #undef  ASM_OUTPUT_ALIGNED_LOCAL
 139 #define ASM_OUTPUT_ALIGNED_LOCAL(FILE, NAME, SIZE, ALIGN)               \
 140 do {                                                                    \
 141   if ((SIZE) <= g_switch_value)                                         \
 142     sbss_section();                                                     \
 143   else                                                                  \
 144     bss_section();                                                      \
 145   ASM_OUTPUT_TYPE_DIRECTIVE (FILE, NAME, "object");                     \
 146   if (!flag_inhibit_size_directive)                                     \
 147     ASM_OUTPUT_SIZE_DIRECTIVE (FILE, NAME, SIZE);                       \
 148   ASM_OUTPUT_ALIGN ((FILE), exact_log2((ALIGN) / BITS_PER_UNIT));       \
 149   ASM_OUTPUT_LABEL(FILE, NAME);                                         \
 150   ASM_OUTPUT_SKIP((FILE), (SIZE) ? (SIZE) : 1);                         \
 151 } while (0)
 152
 153 /* This says how to output assembler code to declare an
 154    uninitialized external linkage data object.  */
 155
 156 #undef  ASM_OUTPUT_ALIGNED_BSS
 157 #define ASM_OUTPUT_ALIGNED_BSS(FILE, DECL, NAME, SIZE, ALIGN)           \
 158 do {                                                                    \
 159   (*targetm.asm_out.globalize_label) (FILE, NAME);                      \
 160   ASM_OUTPUT_ALIGNED_LOCAL (FILE, NAME, SIZE, ALIGN);                   \
 161 } while (0)
 162
 163 /* Biggest alignment supported by the object file format of this
 164    machine.  Use this macro to limit the alignment which can be
 165    specified using the `__attribute__ ((aligned (N)))' construct.  If
 166    not defined, the default value is `BIGGEST_ALIGNMENT'.
 167
 168    This value is really 2^63.  Since gcc figures the alignment in bits,
 169    we could only potentially get to 2^60 on suitible hosts.  Due to other
 170    considerations in varasm, we must restrict this to what fits in an int.  */
 171
 172 #undef  MAX_OFILE_ALIGNMENT
 173 #define MAX_OFILE_ALIGNMENT \
 174   (1 << (HOST_BITS_PER_INT < 64 ? HOST_BITS_PER_INT - 2 : 62))
 175
 176 /* This is the pseudo-op used to generate a contiguous sequence of byte
 177    values from a double-quoted string WITHOUT HAVING A TERMINATING NUL
 178    AUTOMATICALLY APPENDED.  This is the same for most svr4 assemblers.  */
 179
 180 #undef  ASCII_DATA_ASM_OP
 181 #define ASCII_DATA_ASM_OP       "\t.ascii\t"
 182
 183 #undef  READONLY_DATA_SECTION_ASM_OP
 184 #define READONLY_DATA_SECTION_ASM_OP    "\t.section\t.rodata"
 185 #undef  BSS_SECTION_ASM_OP
 186 #define BSS_SECTION_ASM_OP      "\t.section\t.bss"
 187 #undef  SBSS_SECTION_ASM_OP
 188 #define SBSS_SECTION_ASM_OP     "\t.section\t.sbss,\"aw\""
 189 #undef  SDATA_SECTION_ASM_OP
 190 #define SDATA_SECTION_ASM_OP    "\t.section\t.sdata,\"aw\""
 191
 192 /* On svr4, we *do* have support for the .init and .fini sections, and we
 193    can put stuff in there to be executed before and after `main'.  We let
 194    crtstuff.c and other files know this by defining the following symbols.
 195    The definitions say how to change sections to the .init and .fini
 196    sections.  This is the same for all known svr4 assemblers.  */
 197
 198 #undef  INIT_SECTION_ASM_OP
 199 #define INIT_SECTION_ASM_OP     "\t.section\t.init"
 200 #undef  FINI_SECTION_ASM_OP
 201 #define FINI_SECTION_ASM_OP     "\t.section\t.fini"
 202
 203 #ifdef HAVE_GAS_SUBSECTION_ORDERING
 204
 205 #define ASM_SECTION_START_OP    "\t.subsection\t-1"
 206
 207 /* Output assembly directive to move to the beginning of current section.  */
 208 #define ASM_OUTPUT_SECTION_START(FILE)  \
 209   fprintf ((FILE), "%s\n", ASM_SECTION_START_OP)
 210
 211 #endif
 212
 213 /* A default list of other sections which we might be "in" at any given
 214    time.  For targets that use additional sections (e.g. .tdesc) you
 215    should override this definition in the target-specific file which
 216    includes this file.  */
 217
 218 #undef  EXTRA_SECTIONS
 219 #define EXTRA_SECTIONS in_sbss, in_sdata
 220
 221 /* A default list of extra section function definitions.  For targets
 222    that use additional sections (e.g. .tdesc) you should override this
 223    definition in the target-specific file which includes this file.  */
 224
 225 #undef  EXTRA_SECTION_FUNCTIONS
 226 #define EXTRA_SECTION_FUNCTIONS                                         \
 227   SECTION_FUNCTION_TEMPLATE(sbss_section, in_sbss, SBSS_SECTION_ASM_OP) \
 228   SECTION_FUNCTION_TEMPLATE(sdata_section, in_sdata, SDATA_SECTION_ASM_OP)
 229
 230 extern void sbss_section                PARAMS ((void));
 231 extern void sdata_section               PARAMS ((void));
 232
 233 #undef  SECTION_FUNCTION_TEMPLATE
 234 #define SECTION_FUNCTION_TEMPLATE(FN, ENUM, OP) \
 235 void FN ()                                      \
 236 {                                               \
 237   if (in_section != ENUM)                       \
 238     {                                           \
 239       fprintf (asm_out_file, "%s\n", OP);       \
 240       in_section = ENUM;                        \
 241     }                                           \
 242 }
 243
 244 /* Switch into a generic section.  */
 245 #define TARGET_ASM_NAMED_SECTION  default_elf_asm_named_section
 246 #define TARGET_ASM_SELECT_SECTION  default_elf_select_section
 247
 248 #define MAKE_DECL_ONE_ONLY(DECL) (DECL_WEAK (DECL) = 1)
 249
 250 /* Define the strings used for the special svr4 .type and .size directives.
 251    These strings generally do not vary from one system running svr4 to
 252    another, but if a given system (e.g. m88k running svr) needs to use
 253    different pseudo-op names for these, they may be overridden in the
 254    file which includes this one.  */
 255
 256 #undef  TYPE_ASM_OP
 257 #define TYPE_ASM_OP     "\t.type\t"
 258 #undef  SIZE_ASM_OP
 259 #define SIZE_ASM_OP     "\t.size\t"
 260
 261 /* This is how we tell the assembler that a symbol is weak.  */
 262
 263 #undef  ASM_WEAKEN_LABEL
 264 #define ASM_WEAKEN_LABEL(FILE, NAME) \
 265   do { fputs ("\t.weak\t", FILE); assemble_name (FILE, NAME); \
 266        fputc ('\n', FILE); } while (0)
 267
 268 /* This is how we tell the assembler that two symbols have the same value.  */
 269
 270 #undef  ASM_OUTPUT_DEF
 271 #define ASM_OUTPUT_DEF(FILE, ALIAS, NAME)                       \
 272   do {                                                          \
 273     assemble_name(FILE, ALIAS);                                 \
 274     fputs(" = ", FILE);                                         \
 275     assemble_name(FILE, NAME);                                  \
 276     fputc('\n', FILE);                                          \
 277   } while (0)
 278
 279 #undef  ASM_OUTPUT_DEF_FROM_DECLS
 280 #define ASM_OUTPUT_DEF_FROM_DECLS(FILE, DECL, TARGET)           \
 281   do {                                                          \
 282     const char *alias = XSTR (XEXP (DECL_RTL (DECL), 0), 0);    \
 283     const char *name = IDENTIFIER_POINTER (TARGET);             \
 284     if (TREE_CODE (DECL) == FUNCTION_DECL)                      \
 285       {                                                         \
 286         fputc ('$', FILE);                                      \
 287         assemble_name (FILE, alias);                            \
 288         fputs ("..ng = $", FILE);                               \
 289         assemble_name (FILE, name);                             \
 290         fputs ("..ng\n", FILE);                                 \
 291       }                                                         \
 292     assemble_name(FILE, alias);                                 \
 293     fputs(" = ", FILE);                                         \
 294     assemble_name(FILE, name);                                  \
 295     fputc('\n', FILE);                                          \
 296   } while (0)
 297
 298 /* The following macro defines the format used to output the second
 299    operand of the .type assembler directive.  Different svr4 assemblers
 300    expect various different forms for this operand.  The one given here
 301    is just a default.  You may need to override it in your machine-
 302    specific tm.h file (depending upon the particulars of your assembler).  */
 303
 304 #undef  TYPE_OPERAND_FMT
 305 #define TYPE_OPERAND_FMT        "@%s"
 306
 307 /* Write the extra assembler code needed to declare a function's result.
 308    Most svr4 assemblers don't require any special declaration of the
 309    result value, but there are exceptions.  */
 310
 311 #ifndef ASM_DECLARE_RESULT
 312 #define ASM_DECLARE_RESULT(FILE, RESULT)
 313 #endif
 314
 315 /* These macros generate the special .type and .size directives which
 316    are used to set the corresponding fields of the linker symbol table
 317    entries in an ELF object file under SVR4.  These macros also output
 318    the starting labels for the relevant functions/objects.  */
 319
 320 /* Write the extra assembler code needed to declare an object properly.  */
 321
 322 #undef  ASM_DECLARE_OBJECT_NAME
 323 #define ASM_DECLARE_OBJECT_NAME(FILE, NAME, DECL)               \
 324   do {                                                          \
 325     HOST_WIDE_INT size;                                         \
 326     ASM_OUTPUT_TYPE_DIRECTIVE (FILE, NAME, "object");           \
 327     size_directive_output = 0;                                  \
 328     if (!flag_inhibit_size_directive                            \
 329         && DECL_SIZE (DECL)                                     \
 330         && (size = int_size_in_bytes (TREE_TYPE (DECL))) > 0)   \
 331       {                                                         \
 332         size_directive_output = 1;                              \
 333         ASM_OUTPUT_SIZE_DIRECTIVE (FILE, NAME, size);           \
 334       }                                                         \
 335     ASM_OUTPUT_LABEL(FILE, NAME);                               \
 336   } while (0)
 337
 338 /* Output the size directive for a decl in rest_of_decl_compilation
 339    in the case where we did not do so before the initializer.
 340    Once we find the error_mark_node, we know that the value of
 341    size_directive_output was set
 342    by ASM_DECLARE_OBJECT_NAME when it was run for the same decl.  */
 343
 344 #undef  ASM_FINISH_DECLARE_OBJECT
 345 #define ASM_FINISH_DECLARE_OBJECT(FILE, DECL, TOP_LEVEL, AT_END)        \
 346   do {                                                                  \
 347     const char *name = XSTR (XEXP (DECL_RTL (DECL), 0), 0);             \
 348     HOST_WIDE_INT size;                                                 \
 349     if (!flag_inhibit_size_directive                                    \
 350         && DECL_SIZE (DECL)                                             \
 351         && ! AT_END && TOP_LEVEL                                        \
 352         && DECL_INITIAL (DECL) == error_mark_node                       \
 353         && !size_directive_output                                       \
 354         && (size = int_size_in_bytes (TREE_TYPE (DECL))) > 0)           \
 355       {                                                                 \
 356         size_directive_output = 1;                                      \
 357         ASM_OUTPUT_SIZE_DIRECTIVE (FILE, name, size);                   \
 358       }                                                                 \
 359   } while (0)
 360
 361 /* A table of bytes codes used by the ASM_OUTPUT_ASCII and
 362    ASM_OUTPUT_LIMITED_STRING macros.  Each byte in the table
 363    corresponds to a particular byte value [0..255].  For any
 364    given byte value, if the value in the corresponding table
 365    position is zero, the given character can be output directly.
 366    If the table value is 1, the byte must be output as a \ooo
 367    octal escape.  If the tables value is anything else, then the
 368    byte value should be output as a \ followed by the value
 369    in the table.  Note that we can use standard UN*X escape
 370    sequences for many control characters, but we don't use
 371    \a to represent BEL because some svr4 assemblers (e.g. on
 372    the i386) don't know about that.  Also, we don't use \v
 373    since some versions of gas, such as 2.2 did not accept it.  */
 374
 375 #undef  ESCAPES
 376 #define ESCAPES \
 377 "\1\1\1\1\1\1\1\1btn\1fr\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\
 378 \0\0\"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
 379 \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\\\0\0\0\
 380 \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1\
 381 \1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\
 382 \1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\
 383 \1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\
 384 \1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1"
 385
 386 /* Some svr4 assemblers have a limit on the number of characters which
 387    can appear in the operand of a .string directive.  If your assembler
 388    has such a limitation, you should define STRING_LIMIT to reflect that
 389    limit.  Note that at least some svr4 assemblers have a limit on the
 390    actual number of bytes in the double-quoted string, and that they
 391    count each character in an escape sequence as one byte.  Thus, an
 392    escape sequence like \377 would count as four bytes.
 393
 394    If your target assembler doesn't support the .string directive, you
 395    should define this to zero.  */
 396
 397 #undef  STRING_LIMIT
 398 #define STRING_LIMIT    ((unsigned) 256)
 399 #undef  STRING_ASM_OP
 400 #define STRING_ASM_OP   "\t.string\t"
 401
 402 /* GAS is the only Alpha/ELF assembler.  */
 403 #undef  TARGET_GAS
 404 #define TARGET_GAS      (1)
 405
 406 /* Provide a STARTFILE_SPEC appropriate for ELF.  Here we add the
 407    (even more) magical crtbegin.o file which provides part of the
 408    support for getting C++ file-scope static object constructed
 409    before entering `main'.   */
 410
 411 #undef  STARTFILE_SPEC
 412 #define STARTFILE_SPEC \
 413   "%{!shared: \
 414      %{pg:gcrt1.o%s} %{!pg:%{p:gcrt1.o%s} %{!p:crt1.o%s}}}\
 415    crti.o%s %{static:crtbeginT.o%s}\
 416    %{!static:%{shared:crtbeginS.o%s}%{!shared:crtbegin.o%s}}"
 417
 418 /* Provide a ENDFILE_SPEC appropriate for ELF.  Here we tack on the
 419    magical crtend.o file which provides part of the support for
 420    getting C++ file-scope static object constructed before entering
 421    `main', followed by a normal ELF "finalizer" file, `crtn.o'.  */
 422
 423 #undef  ENDFILE_SPEC
 424 #define ENDFILE_SPEC \
 425   "%{ffast-math|funsafe-math-optimizations:crtfastmath.o%s} \
 426    %{shared:crtendS.o%s}%{!shared:crtend.o%s} crtn.o%s"
 427
 428 /* We support #pragma.  */
 429 #define HANDLE_SYSV_PRAGMA 1
 430
 431 /* Select a format to encode pointers in exception handling data.  CODE
 432    is 0 for data, 1 for code labels, 2 for function pointers.  GLOBAL is
 433    true if the symbol may be affected by dynamic relocations.
 434
 435    Since application size is already constrained to <2GB by the form of
 436    the ldgp relocation, we can use a 32-bit pc-relative relocation to
 437    static data.  Dynamic data is accessed indirectly to allow for read
 438    only EH sections.  */
 439 #define ASM_PREFERRED_EH_DATA_FORMAT(CODE,GLOBAL)       \
 440   (((GLOBAL) ? DW_EH_PE_indirect : 0) | DW_EH_PE_pcrel | DW_EH_PE_sdata4)
 441
 442 /* If defined, a C statement to be executed just prior to the output of
 443    assembler code for INSN.  */
 444 #define FINAL_PRESCAN_INSN(INSN, OPVEC, NOPERANDS)      \
 445  (alpha_this_literal_sequence_number = 0,               \
 446   alpha_this_gpdisp_sequence_number = 0)
 447 extern int alpha_this_literal_sequence_number;
 448 extern int alpha_this_gpdisp_sequence_number;
 449
 450 /* Since the bits of the _init and _fini function is spread across
 451    many object files, each potentially with its own GP, we must assume
 452    we need to load our GP.  Further, the .init/.fini section can
 453    easily be more than 4MB away from the function to call so we can't
 454    use bsr.  */
 455 #define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC)      \
 456    asm (SECTION_OP "\n"                                 \
 457 "       br $29,1f\n"                                    \
 458 "1:     ldgp $29,0($29)\n"                              \
 459 "       unop\n"                                         \
 460 "       jsr $26," USER_LABEL_PREFIX #FUNC "\n"          \
 461 "       .align 3\n"                                     \
 462 "       .previous");
 463
 464 /* If we have the capability create headers for efficient EH lookup.
 465    As of Jan 2002, only glibc 2.2.4 can actually make use of this, but
 466    I imagine that other systems will catch up.  In the meantime, it
 467    doesn't harm to make sure that the data exists to be used later.  */
 468 #if defined(HAVE_LD_EH_FRAME_HDR)
 469 #define LINK_EH_SPEC "%{!static:--eh-frame-hdr} "
 470 #endif