targets.texi revision 1.1.1.7
1@section Targets 2 3 4@strong{Description}@* 5Each port of BFD to a different machine requires the creation 6of a target back end. All the back end provides to the root 7part of BFD is a structure containing pointers to functions 8which perform certain low level operations on files. BFD 9translates the applications's requests through a pointer into 10calls to the back end routines. 11 12When a file is opened with @code{bfd_openr}, its format and 13target are unknown. BFD uses various mechanisms to determine 14how to interpret the file. The operations performed are: 15 16@itemize @bullet 17 18@item 19Create a BFD by calling the internal routine 20@code{_bfd_new_bfd}, then call @code{bfd_find_target} with the 21target string supplied to @code{bfd_openr} and the new BFD pointer. 22 23@item 24If a null target string was provided to @code{bfd_find_target}, 25look up the environment variable @code{GNUTARGET} and use 26that as the target string. 27 28@item 29If the target string is still @code{NULL}, or the target string is 30@code{default}, then use the first item in the target vector 31as the target type, and set @code{target_defaulted} in the BFD to 32cause @code{bfd_check_format} to loop through all the targets. 33@xref{bfd_target}. @xref{Formats}. 34 35@item 36Otherwise, inspect the elements in the target vector 37one by one, until a match on target name is found. When found, 38use it. 39 40@item 41Otherwise return the error @code{bfd_error_invalid_target} to 42@code{bfd_openr}. 43 44@item 45@code{bfd_openr} attempts to open the file using 46@code{bfd_open_file}, and returns the BFD. 47@end itemize 48Once the BFD has been opened and the target selected, the file 49format may be determined. This is done by calling 50@code{bfd_check_format} on the BFD with a suggested format. 51If @code{target_defaulted} has been set, each possible target 52type is tried to see if it recognizes the specified format. 53@code{bfd_check_format} returns @code{TRUE} when the caller guesses right. 54@menu 55* bfd_target:: 56@end menu 57 58@node bfd_target, , Targets, Targets 59 60@subsection bfd_target 61 62 63@strong{Description}@* 64This structure contains everything that BFD knows about a 65target. It includes things like its byte order, name, and which 66routines to call to do various operations. 67 68Every BFD points to a target structure with its @code{xvec} 69member. 70 71The macros below are used to dispatch to functions through the 72@code{bfd_target} vector. They are used in a number of macros further 73down in @file{bfd.h}, and are also used when calling various 74routines by hand inside the BFD implementation. The @var{arglist} 75argument must be parenthesized; it contains all the arguments 76to the called function. 77 78They make the documentation (more) unpleasant to read, so if 79someone wants to fix this and not break the above, please do. 80@example 81#define BFD_SEND(bfd, message, arglist) \ 82 ((*((bfd)->xvec->message)) arglist) 83 84#ifdef DEBUG_BFD_SEND 85#undef BFD_SEND 86#define BFD_SEND(bfd, message, arglist) \ 87 (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \ 88 ((*((bfd)->xvec->message)) arglist) : \ 89 (bfd_assert (__FILE__,__LINE__), NULL)) 90#endif 91@end example 92For operations which index on the BFD format: 93@example 94#define BFD_SEND_FMT(bfd, message, arglist) \ 95 (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist) 96 97#ifdef DEBUG_BFD_SEND 98#undef BFD_SEND_FMT 99#define BFD_SEND_FMT(bfd, message, arglist) \ 100 (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \ 101 (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist) : \ 102 (bfd_assert (__FILE__,__LINE__), NULL)) 103#endif 104 105@end example 106This is the structure which defines the type of BFD this is. The 107@code{xvec} member of the struct @code{bfd} itself points here. Each 108module that implements access to a different target under BFD, 109defines one of these. 110 111FIXME, these names should be rationalised with the names of 112the entry points which call them. Too bad we can't have one 113macro to define them both! 114@example 115enum bfd_flavour 116@{ 117 /* N.B. Update bfd_flavour_name if you change this. */ 118 bfd_target_unknown_flavour, 119 bfd_target_aout_flavour, 120 bfd_target_coff_flavour, 121 bfd_target_ecoff_flavour, 122 bfd_target_xcoff_flavour, 123 bfd_target_elf_flavour, 124 bfd_target_tekhex_flavour, 125 bfd_target_srec_flavour, 126 bfd_target_verilog_flavour, 127 bfd_target_ihex_flavour, 128 bfd_target_som_flavour, 129 bfd_target_os9k_flavour, 130 bfd_target_versados_flavour, 131 bfd_target_msdos_flavour, 132 bfd_target_ovax_flavour, 133 bfd_target_evax_flavour, 134 bfd_target_mmo_flavour, 135 bfd_target_mach_o_flavour, 136 bfd_target_pef_flavour, 137 bfd_target_pef_xlib_flavour, 138 bfd_target_sym_flavour 139@}; 140 141enum bfd_endian @{ BFD_ENDIAN_BIG, BFD_ENDIAN_LITTLE, BFD_ENDIAN_UNKNOWN @}; 142 143/* Forward declaration. */ 144typedef struct bfd_link_info _bfd_link_info; 145 146/* Forward declaration. */ 147typedef struct flag_info flag_info; 148 149typedef struct bfd_target 150@{ 151 /* Identifies the kind of target, e.g., SunOS4, Ultrix, etc. */ 152 char *name; 153 154 /* The "flavour" of a back end is a general indication about 155 the contents of a file. */ 156 enum bfd_flavour flavour; 157 158 /* The order of bytes within the data area of a file. */ 159 enum bfd_endian byteorder; 160 161 /* The order of bytes within the header parts of a file. */ 162 enum bfd_endian header_byteorder; 163 164 /* A mask of all the flags which an executable may have set - 165 from the set @code{BFD_NO_FLAGS}, @code{HAS_RELOC}, ...@code{D_PAGED}. */ 166 flagword object_flags; 167 168 /* A mask of all the flags which a section may have set - from 169 the set @code{SEC_NO_FLAGS}, @code{SEC_ALLOC}, ...@code{SET_NEVER_LOAD}. */ 170 flagword section_flags; 171 172 /* The character normally found at the front of a symbol. 173 (if any), perhaps `_'. */ 174 char symbol_leading_char; 175 176 /* The pad character for file names within an archive header. */ 177 char ar_pad_char; 178 179 /* The maximum number of characters in an archive header. */ 180 unsigned char ar_max_namelen; 181 182 /* How well this target matches, used to select between various 183 possible targets when more than one target matches. */ 184 unsigned char match_priority; 185 186 /* Entries for byte swapping for data. These are different from the 187 other entry points, since they don't take a BFD as the first argument. 188 Certain other handlers could do the same. */ 189 bfd_uint64_t (*bfd_getx64) (const void *); 190 bfd_int64_t (*bfd_getx_signed_64) (const void *); 191 void (*bfd_putx64) (bfd_uint64_t, void *); 192 bfd_vma (*bfd_getx32) (const void *); 193 bfd_signed_vma (*bfd_getx_signed_32) (const void *); 194 void (*bfd_putx32) (bfd_vma, void *); 195 bfd_vma (*bfd_getx16) (const void *); 196 bfd_signed_vma (*bfd_getx_signed_16) (const void *); 197 void (*bfd_putx16) (bfd_vma, void *); 198 199 /* Byte swapping for the headers. */ 200 bfd_uint64_t (*bfd_h_getx64) (const void *); 201 bfd_int64_t (*bfd_h_getx_signed_64) (const void *); 202 void (*bfd_h_putx64) (bfd_uint64_t, void *); 203 bfd_vma (*bfd_h_getx32) (const void *); 204 bfd_signed_vma (*bfd_h_getx_signed_32) (const void *); 205 void (*bfd_h_putx32) (bfd_vma, void *); 206 bfd_vma (*bfd_h_getx16) (const void *); 207 bfd_signed_vma (*bfd_h_getx_signed_16) (const void *); 208 void (*bfd_h_putx16) (bfd_vma, void *); 209 210 /* Format dependent routines: these are vectors of entry points 211 within the target vector structure, one for each format to check. */ 212 213 /* Check the format of a file being read. Return a @code{bfd_target *} or zero. */ 214 const struct bfd_target * 215 (*_bfd_check_format[bfd_type_end]) (bfd *); 216 217 /* Set the format of a file being written. */ 218 bfd_boolean (*_bfd_set_format[bfd_type_end]) (bfd *); 219 220 /* Write cached information into a file being written, at @code{bfd_close}. */ 221 bfd_boolean (*_bfd_write_contents[bfd_type_end]) (bfd *); 222 223@end example 224The general target vector. These vectors are initialized using the 225BFD_JUMP_TABLE macros. 226@example 227 228 /* Generic entry points. */ 229#define BFD_JUMP_TABLE_GENERIC(NAME) \ 230 NAME##_close_and_cleanup, \ 231 NAME##_bfd_free_cached_info, \ 232 NAME##_new_section_hook, \ 233 NAME##_get_section_contents, \ 234 NAME##_get_section_contents_in_window 235 236 /* Called when the BFD is being closed to do any necessary cleanup. */ 237 bfd_boolean (*_close_and_cleanup) (bfd *); 238 /* Ask the BFD to free all cached information. */ 239 bfd_boolean (*_bfd_free_cached_info) (bfd *); 240 /* Called when a new section is created. */ 241 bfd_boolean (*_new_section_hook) (bfd *, sec_ptr); 242 /* Read the contents of a section. */ 243 bfd_boolean (*_bfd_get_section_contents) (bfd *, sec_ptr, void *, file_ptr, 244 bfd_size_type); 245 bfd_boolean (*_bfd_get_section_contents_in_window) (bfd *, sec_ptr, 246 bfd_window *, file_ptr, 247 bfd_size_type); 248 249 /* Entry points to copy private data. */ 250#define BFD_JUMP_TABLE_COPY(NAME) \ 251 NAME##_bfd_copy_private_bfd_data, \ 252 NAME##_bfd_merge_private_bfd_data, \ 253 _bfd_generic_init_private_section_data, \ 254 NAME##_bfd_copy_private_section_data, \ 255 NAME##_bfd_copy_private_symbol_data, \ 256 NAME##_bfd_copy_private_header_data, \ 257 NAME##_bfd_set_private_flags, \ 258 NAME##_bfd_print_private_bfd_data 259 260 /* Called to copy BFD general private data from one object file 261 to another. */ 262 bfd_boolean (*_bfd_copy_private_bfd_data) (bfd *, bfd *); 263 /* Called to merge BFD general private data from one object file 264 to a common output file when linking. */ 265 bfd_boolean (*_bfd_merge_private_bfd_data) (bfd *, struct bfd_link_info *); 266 /* Called to initialize BFD private section data from one object file 267 to another. */ 268#define bfd_init_private_section_data(ibfd, isec, obfd, osec, link_info) \ 269 BFD_SEND (obfd, _bfd_init_private_section_data, \ 270 (ibfd, isec, obfd, osec, link_info)) 271 bfd_boolean (*_bfd_init_private_section_data) (bfd *, sec_ptr, bfd *, 272 sec_ptr, 273 struct bfd_link_info *); 274 /* Called to copy BFD private section data from one object file 275 to another. */ 276 bfd_boolean (*_bfd_copy_private_section_data) (bfd *, sec_ptr, bfd *, 277 sec_ptr); 278 /* Called to copy BFD private symbol data from one symbol 279 to another. */ 280 bfd_boolean (*_bfd_copy_private_symbol_data) (bfd *, asymbol *, bfd *, 281 asymbol *); 282 /* Called to copy BFD private header data from one object file 283 to another. */ 284 bfd_boolean (*_bfd_copy_private_header_data) (bfd *, bfd *); 285 /* Called to set private backend flags. */ 286 bfd_boolean (*_bfd_set_private_flags) (bfd *, flagword); 287 288 /* Called to print private BFD data. */ 289 bfd_boolean (*_bfd_print_private_bfd_data) (bfd *, void *); 290 291 /* Core file entry points. */ 292#define BFD_JUMP_TABLE_CORE(NAME) \ 293 NAME##_core_file_failing_command, \ 294 NAME##_core_file_failing_signal, \ 295 NAME##_core_file_matches_executable_p, \ 296 NAME##_core_file_pid 297 298 char * (*_core_file_failing_command) (bfd *); 299 int (*_core_file_failing_signal) (bfd *); 300 bfd_boolean (*_core_file_matches_executable_p) (bfd *, bfd *); 301 int (*_core_file_pid) (bfd *); 302 303 /* Archive entry points. */ 304#define BFD_JUMP_TABLE_ARCHIVE(NAME) \ 305 NAME##_slurp_armap, \ 306 NAME##_slurp_extended_name_table, \ 307 NAME##_construct_extended_name_table, \ 308 NAME##_truncate_arname, \ 309 NAME##_write_armap, \ 310 NAME##_read_ar_hdr, \ 311 NAME##_write_ar_hdr, \ 312 NAME##_openr_next_archived_file, \ 313 NAME##_get_elt_at_index, \ 314 NAME##_generic_stat_arch_elt, \ 315 NAME##_update_armap_timestamp 316 317 bfd_boolean (*_bfd_slurp_armap) (bfd *); 318 bfd_boolean (*_bfd_slurp_extended_name_table) (bfd *); 319 bfd_boolean (*_bfd_construct_extended_name_table) (bfd *, char **, 320 bfd_size_type *, 321 const char **); 322 void (*_bfd_truncate_arname) (bfd *, const char *, char *); 323 bfd_boolean (*write_armap) (bfd *, unsigned int, struct orl *, 324 unsigned int, int); 325 void * (*_bfd_read_ar_hdr_fn) (bfd *); 326 bfd_boolean (*_bfd_write_ar_hdr_fn) (bfd *, bfd *); 327 bfd * (*openr_next_archived_file) (bfd *, bfd *); 328#define bfd_get_elt_at_index(b,i) \ 329 BFD_SEND (b, _bfd_get_elt_at_index, (b,i)) 330 bfd * (*_bfd_get_elt_at_index) (bfd *, symindex); 331 int (*_bfd_stat_arch_elt) (bfd *, struct stat *); 332 bfd_boolean (*_bfd_update_armap_timestamp) (bfd *); 333 334 /* Entry points used for symbols. */ 335#define BFD_JUMP_TABLE_SYMBOLS(NAME) \ 336 NAME##_get_symtab_upper_bound, \ 337 NAME##_canonicalize_symtab, \ 338 NAME##_make_empty_symbol, \ 339 NAME##_print_symbol, \ 340 NAME##_get_symbol_info, \ 341 NAME##_get_symbol_version_string, \ 342 NAME##_bfd_is_local_label_name, \ 343 NAME##_bfd_is_target_special_symbol, \ 344 NAME##_get_lineno, \ 345 NAME##_find_nearest_line, \ 346 NAME##_find_line, \ 347 NAME##_find_inliner_info, \ 348 NAME##_bfd_make_debug_symbol, \ 349 NAME##_read_minisymbols, \ 350 NAME##_minisymbol_to_symbol 351 352 long (*_bfd_get_symtab_upper_bound) (bfd *); 353 long (*_bfd_canonicalize_symtab) (bfd *, struct bfd_symbol **); 354 struct bfd_symbol * 355 (*_bfd_make_empty_symbol) (bfd *); 356 void (*_bfd_print_symbol) (bfd *, void *, struct bfd_symbol *, 357 bfd_print_symbol_type); 358#define bfd_print_symbol(b,p,s,e) \ 359 BFD_SEND (b, _bfd_print_symbol, (b,p,s,e)) 360 void (*_bfd_get_symbol_info) (bfd *, struct bfd_symbol *, 361 symbol_info *); 362#define bfd_get_symbol_info(b,p,e) \ 363 BFD_SEND (b, _bfd_get_symbol_info, (b,p,e)) 364 const char *(*_bfd_get_symbol_version_string) (bfd *, struct bfd_symbol *, 365 bfd_boolean *); 366#define bfd_get_symbol_version_string(b,s,h) \ 367 BFD_SEND (b, _bfd_get_symbol_version_string, (b,s,h)) 368 bfd_boolean (*_bfd_is_local_label_name) (bfd *, const char *); 369 bfd_boolean (*_bfd_is_target_special_symbol) (bfd *, asymbol *); 370 alent * (*_get_lineno) (bfd *, struct bfd_symbol *); 371 bfd_boolean (*_bfd_find_nearest_line) (bfd *, struct bfd_symbol **, 372 struct bfd_section *, bfd_vma, 373 const char **, const char **, 374 unsigned int *, unsigned int *); 375 bfd_boolean (*_bfd_find_line) (bfd *, struct bfd_symbol **, 376 struct bfd_symbol *, const char **, 377 unsigned int *); 378 bfd_boolean (*_bfd_find_inliner_info) 379 (bfd *, const char **, const char **, unsigned int *); 380 /* Back-door to allow format-aware applications to create debug symbols 381 while using BFD for everything else. Currently used by the assembler 382 when creating COFF files. */ 383 asymbol * (*_bfd_make_debug_symbol) (bfd *, void *, unsigned long size); 384#define bfd_read_minisymbols(b, d, m, s) \ 385 BFD_SEND (b, _read_minisymbols, (b, d, m, s)) 386 long (*_read_minisymbols) (bfd *, bfd_boolean, void **, 387 unsigned int *); 388#define bfd_minisymbol_to_symbol(b, d, m, f) \ 389 BFD_SEND (b, _minisymbol_to_symbol, (b, d, m, f)) 390 asymbol * (*_minisymbol_to_symbol) (bfd *, bfd_boolean, const void *, 391 asymbol *); 392 393 /* Routines for relocs. */ 394#define BFD_JUMP_TABLE_RELOCS(NAME) \ 395 NAME##_get_reloc_upper_bound, \ 396 NAME##_canonicalize_reloc, \ 397 NAME##_set_reloc, \ 398 NAME##_bfd_reloc_type_lookup, \ 399 NAME##_bfd_reloc_name_lookup 400 401 long (*_get_reloc_upper_bound) (bfd *, sec_ptr); 402 long (*_bfd_canonicalize_reloc) (bfd *, sec_ptr, arelent **, 403 struct bfd_symbol **); 404 void (*_bfd_set_reloc) (bfd *, sec_ptr, arelent **, unsigned int); 405 /* See documentation on reloc types. */ 406 reloc_howto_type * 407 (*reloc_type_lookup) (bfd *, bfd_reloc_code_real_type); 408 reloc_howto_type * 409 (*reloc_name_lookup) (bfd *, const char *); 410 411 /* Routines used when writing an object file. */ 412#define BFD_JUMP_TABLE_WRITE(NAME) \ 413 NAME##_set_arch_mach, \ 414 NAME##_set_section_contents 415 416 bfd_boolean (*_bfd_set_arch_mach) (bfd *, enum bfd_architecture, 417 unsigned long); 418 bfd_boolean (*_bfd_set_section_contents) (bfd *, sec_ptr, const void *, 419 file_ptr, bfd_size_type); 420 421 /* Routines used by the linker. */ 422#define BFD_JUMP_TABLE_LINK(NAME) \ 423 NAME##_sizeof_headers, \ 424 NAME##_bfd_get_relocated_section_contents, \ 425 NAME##_bfd_relax_section, \ 426 NAME##_bfd_link_hash_table_create, \ 427 NAME##_bfd_link_add_symbols, \ 428 NAME##_bfd_link_just_syms, \ 429 NAME##_bfd_copy_link_hash_symbol_type, \ 430 NAME##_bfd_final_link, \ 431 NAME##_bfd_link_split_section, \ 432 NAME##_bfd_link_check_relocs, \ 433 NAME##_bfd_gc_sections, \ 434 NAME##_bfd_lookup_section_flags, \ 435 NAME##_bfd_merge_sections, \ 436 NAME##_bfd_is_group_section, \ 437 NAME##_bfd_discard_group, \ 438 NAME##_section_already_linked, \ 439 NAME##_bfd_define_common_symbol, \ 440 NAME##_bfd_link_hide_symbol, \ 441 NAME##_bfd_define_start_stop 442 443 int (*_bfd_sizeof_headers) (bfd *, struct bfd_link_info *); 444 bfd_byte * (*_bfd_get_relocated_section_contents) (bfd *, 445 struct bfd_link_info *, 446 struct bfd_link_order *, 447 bfd_byte *, bfd_boolean, 448 struct bfd_symbol **); 449 450 bfd_boolean (*_bfd_relax_section) (bfd *, struct bfd_section *, 451 struct bfd_link_info *, bfd_boolean *); 452 453 /* Create a hash table for the linker. Different backends store 454 different information in this table. */ 455 struct bfd_link_hash_table * 456 (*_bfd_link_hash_table_create) (bfd *); 457 458 /* Add symbols from this object file into the hash table. */ 459 bfd_boolean (*_bfd_link_add_symbols) (bfd *, struct bfd_link_info *); 460 461 /* Indicate that we are only retrieving symbol values from this section. */ 462 void (*_bfd_link_just_syms) (asection *, struct bfd_link_info *); 463 464 /* Copy the symbol type and other attributes for a linker script 465 assignment of one symbol to another. */ 466#define bfd_copy_link_hash_symbol_type(b, t, f) \ 467 BFD_SEND (b, _bfd_copy_link_hash_symbol_type, (b, t, f)) 468 void (*_bfd_copy_link_hash_symbol_type) (bfd *, 469 struct bfd_link_hash_entry *, 470 struct bfd_link_hash_entry *); 471 472 /* Do a link based on the link_order structures attached to each 473 section of the BFD. */ 474 bfd_boolean (*_bfd_final_link) (bfd *, struct bfd_link_info *); 475 476 /* Should this section be split up into smaller pieces during linking. */ 477 bfd_boolean (*_bfd_link_split_section) (bfd *, struct bfd_section *); 478 479 /* Check the relocations in the bfd for validity. */ 480 bfd_boolean (* _bfd_link_check_relocs)(bfd *, struct bfd_link_info *); 481 482 /* Remove sections that are not referenced from the output. */ 483 bfd_boolean (*_bfd_gc_sections) (bfd *, struct bfd_link_info *); 484 485 /* Sets the bitmask of allowed and disallowed section flags. */ 486 bfd_boolean (*_bfd_lookup_section_flags) (struct bfd_link_info *, 487 struct flag_info *, asection *); 488 489 /* Attempt to merge SEC_MERGE sections. */ 490 bfd_boolean (*_bfd_merge_sections) (bfd *, struct bfd_link_info *); 491 492 /* Is this section a member of a group? */ 493 bfd_boolean (*_bfd_is_group_section) (bfd *, const struct bfd_section *); 494 495 /* Discard members of a group. */ 496 bfd_boolean (*_bfd_discard_group) (bfd *, struct bfd_section *); 497 498 /* Check if SEC has been already linked during a reloceatable or 499 final link. */ 500 bfd_boolean (*_section_already_linked) (bfd *, asection *, 501 struct bfd_link_info *); 502 503 /* Define a common symbol. */ 504 bfd_boolean (*_bfd_define_common_symbol) (bfd *, struct bfd_link_info *, 505 struct bfd_link_hash_entry *); 506 507 /* Hide a symbol. */ 508 void (*_bfd_link_hide_symbol) (bfd *, struct bfd_link_info *, 509 struct bfd_link_hash_entry *); 510 511 /* Define a __start, __stop, .startof. or .sizeof. symbol. */ 512 struct bfd_link_hash_entry * 513 (*_bfd_define_start_stop) (struct bfd_link_info *, const char *, 514 asection *); 515 516 /* Routines to handle dynamic symbols and relocs. */ 517#define BFD_JUMP_TABLE_DYNAMIC(NAME) \ 518 NAME##_get_dynamic_symtab_upper_bound, \ 519 NAME##_canonicalize_dynamic_symtab, \ 520 NAME##_get_synthetic_symtab, \ 521 NAME##_get_dynamic_reloc_upper_bound, \ 522 NAME##_canonicalize_dynamic_reloc 523 524 /* Get the amount of memory required to hold the dynamic symbols. */ 525 long (*_bfd_get_dynamic_symtab_upper_bound) (bfd *); 526 /* Read in the dynamic symbols. */ 527 long (*_bfd_canonicalize_dynamic_symtab) (bfd *, struct bfd_symbol **); 528 /* Create synthetized symbols. */ 529 long (*_bfd_get_synthetic_symtab) (bfd *, long, struct bfd_symbol **, 530 long, struct bfd_symbol **, 531 struct bfd_symbol **); 532 /* Get the amount of memory required to hold the dynamic relocs. */ 533 long (*_bfd_get_dynamic_reloc_upper_bound) (bfd *); 534 /* Read in the dynamic relocs. */ 535 long (*_bfd_canonicalize_dynamic_reloc) (bfd *, arelent **, 536 struct bfd_symbol **); 537 538@end example 539A pointer to an alternative bfd_target in case the current one is not 540satisfactory. This can happen when the target cpu supports both big 541and little endian code, and target chosen by the linker has the wrong 542endianness. The function open_output() in ld/ldlang.c uses this field 543to find an alternative output format that is suitable. 544@example 545 /* Opposite endian version of this target. */ 546 const struct bfd_target *alternative_target; 547 548 /* Data for use by back-end routines, which isn't 549 generic enough to belong in this structure. */ 550 const void *backend_data; 551 552@} bfd_target; 553 554@end example 555 556@findex bfd_set_default_target 557@subsubsection @code{bfd_set_default_target} 558@strong{Synopsis} 559@example 560bfd_boolean bfd_set_default_target (const char *name); 561@end example 562@strong{Description}@* 563Set the default target vector to use when recognizing a BFD. 564This takes the name of the target, which may be a BFD target 565name or a configuration triplet. 566 567@findex bfd_find_target 568@subsubsection @code{bfd_find_target} 569@strong{Synopsis} 570@example 571const bfd_target *bfd_find_target (const char *target_name, bfd *abfd); 572@end example 573@strong{Description}@* 574Return a pointer to the transfer vector for the object target 575named @var{target_name}. If @var{target_name} is @code{NULL}, 576choose the one in the environment variable @code{GNUTARGET}; if 577that is null or not defined, then choose the first entry in the 578target list. Passing in the string "default" or setting the 579environment variable to "default" will cause the first entry in 580the target list to be returned, and "target_defaulted" will be 581set in the BFD if @var{abfd} isn't @code{NULL}. This causes 582@code{bfd_check_format} to loop over all the targets to find the 583one that matches the file being read. 584 585@findex bfd_get_target_info 586@subsubsection @code{bfd_get_target_info} 587@strong{Synopsis} 588@example 589const bfd_target *bfd_get_target_info (const char *target_name, 590 bfd *abfd, 591 bfd_boolean *is_bigendian, 592 int *underscoring, 593 const char **def_target_arch); 594@end example 595@strong{Description}@* 596Return a pointer to the transfer vector for the object target 597named @var{target_name}. If @var{target_name} is @code{NULL}, 598choose the one in the environment variable @code{GNUTARGET}; if 599that is null or not defined, then choose the first entry in the 600target list. Passing in the string "default" or setting the 601environment variable to "default" will cause the first entry in 602the target list to be returned, and "target_defaulted" will be 603set in the BFD if @var{abfd} isn't @code{NULL}. This causes 604@code{bfd_check_format} to loop over all the targets to find the 605one that matches the file being read. 606If @var{is_bigendian} is not @code{NULL}, then set this value to target's 607endian mode. True for big-endian, FALSE for little-endian or for 608invalid target. 609If @var{underscoring} is not @code{NULL}, then set this value to target's 610underscoring mode. Zero for none-underscoring, -1 for invalid target, 611else the value of target vector's symbol underscoring. 612If @var{def_target_arch} is not @code{NULL}, then set it to the architecture 613string specified by the target_name. 614 615@findex bfd_target_list 616@subsubsection @code{bfd_target_list} 617@strong{Synopsis} 618@example 619const char ** bfd_target_list (void); 620@end example 621@strong{Description}@* 622Return a freshly malloced NULL-terminated 623vector of the names of all the valid BFD targets. Do not 624modify the names. 625 626@findex bfd_iterate_over_targets 627@subsubsection @code{bfd_iterate_over_targets} 628@strong{Synopsis} 629@example 630const bfd_target *bfd_iterate_over_targets 631 (int (*func) (const bfd_target *, void *), 632 void *data); 633@end example 634@strong{Description}@* 635Call @var{func} for each target in the list of BFD target 636vectors, passing @var{data} to @var{func}. Stop iterating if 637@var{func} returns a non-zero result, and return that target 638vector. Return NULL if @var{func} always returns zero. 639 640@findex bfd_flavour_name 641@subsubsection @code{bfd_flavour_name} 642@strong{Synopsis} 643@example 644const char *bfd_flavour_name (enum bfd_flavour flavour); 645@end example 646@strong{Description}@* 647Return the string form of @var{flavour}. 648 649