ld/NEWS

   1 -*- text -*-
   2
   3 * Add -z unique-symbol to avoid duplicated local symbol names.
   4
   5 * The creation of PE format DLLs now defaults to using a more secure set of DLL
   6   characteristics.
   7
   8 * The linker now deduplicates the types in .ctf sections.  The new
   9   command-line option --ctf-share-types describes how to do this:
  10   its default value, share-unconflicted, produces the most compact
  11   output.
  12
  13 * The linker now omits the "variable section" from .ctf sections by
  14   default, saving space.  This is almost certainly what you want
  15   unless you are working on a project that has its own analogue
  16   of symbol tables that are not reflected in the ELF symtabs.
  17
  18 Changes in 2.35:
  19
  20 * X86 NaCl target support is removed.
  21
  22 * Add ELF linker command-line options, --export-dynamic-symbol and
  23   --export-dynamic-symbol-list, to make symbols dynamic.
  24
  25 * Add a configure option, --enable-textrel-check=[no|yes|warning|error],
  26   to decide what ELF linker should do by default with DT_TEXTREL in an
  27   executable or shared library.  Default to yes for Linux/x86 targets.
  28
  29 * The -Map=<filename> command line option has been extended so that if
  30   <filename> is a directory then <filename>/<output-filename>.map will be
  31   created.
  32
  33 * Add a command-line option for ELF linker, --warn-textrel, to warn that
  34   DT_TEXTREL is set in a position-independent executable or shared object.
  35
  36 * Add command-line options --enable-non-contiguous-regions and
  37   --enable-non-contiguous-regions-warnings.
  38
  39 * Add command-line option --imagic for the pdp11-aout target to output format
  40   IMAGIC (0411) for separate instruction and data spaces, and change the
  41   default format option for pdp11-aout to be --omagic.
  42
  43 * Relative pathnames in INPUT() and GROUP() directives in linker scripts are
  44   searched relative to the directory of the linker script before other search
  45   paths.
  46
  47 * Add ELF linker command-line option `-z start-stop-visibility=...' to control
  48   the visibility of synthetic `__start_SECNAME` and `__stop_SECNAME` symbols.
  49
  50 * Add command-line option --dependency-file to write a Make-style dependency
  51   file listing the input files consulted by the linker, like the files written
  52   by the compiler's -M -MP options.
  53
  54 Changes in 2.34:
  55
  56 * The ld check for "PHDR segment not covered by LOAD segment" is more
  57   effective, catching cases that were wrongly allowed by previous versions of
  58   ld.  If you see this error it is likely you are linking with a bad linker
  59   script or the binary you are building is not intended to be loaded by a
  60   dynamic loader.  In the latter case --no-dynamic-linker is appropriate.
  61
  62 * cr16c support removed.
  63
  64 * Add support for z80-elf.
  65
  66 * Add support for relocation of each byte or word of multibyte value to Z80
  67   targets.
  68
  69 * Add support for Zilog eZ80 (both ADL and Z80 mode) and Zilog Z180 CPUs.
  70
  71 Changes in 2.33:
  72
  73 * Add command-line option --no-print-map-discarded.
  74
  75 * The Cortex-A53 Erratum 843419 workaround now supports a choice of which
  76   workaround to use.  The option --fix-cortex-a53-843419 now takes an
  77   optional argument --fix-cortex-a53-843419[=full|adr|adrp] which can be
  78   used to force a particular workaround to be used.  See --help for AArch64
  79   for more details.
  80
  81 * Add target handlers for AArch64 for ELF GNU program properties.
  82
  83 * Add support for GNU_PROPERTY_AARCH64_FEATURE_1_BTI in ELF GNU program
  84   properties in the AArch64 ELF linker.
  85
  86 * Add support for GNU_PROPERTY_AARCH64_FEATURE_1_PAC in ELF GNU program
  87   properties in the AArch64 ELF linker.
  88
  89 * Add -z force-bti for AArch64 to enable GNU_PROPERTY_AARCH64_FEATURE_1_BTI
  90   on output while warning about missing GNU_PROPERTY_AARCH64_FEATURE_1_BTI
  91   on inputs and use PLTs protected with BTI.
  92
  93 * Add -z pac-plt for AArch64 to pick PAC enabled PLTs.
  94
  95 Changes in 2.32:
  96
  97 * Report property change in linker map file when merging GNU properties.
  98
  99 * Add support for the C-SKY processor series.
 100
 101 * -t now doesn't report members within archives, unless -t is given twice.
 102   A single -t is now more useful when generating a list of files that should be
 103   packaged for a linker bug report.  For example:
 104     gcc hello.c -save-temps -Wl,-t | xargs realpath | sort | uniq > files
 105     tar cJf test.tar.xz `cat files`
 106
 107 Changes in 2.31:
 108
 109 * Speed up direct linking with DLLs for Cygwin and Mingw targets.
 110
 111 * Add a configure option --enable-separate-code to decide whether
 112   -z separate-code should be enabled in ELF linker by default.  Default
 113   to yes for Linux/x86 targets.  Note that -z separate-code can increase
 114   disk and memory size.
 115
 116 Changes in 2.30:
 117
 118 * Add -z separate-code to generate separate code PT_LOAD segment.
 119
 120 * Add "-z undefs" command-line option as the inverse of the "-z defs" option.
 121
 122 * Add -z globalaudit command-line option to force audit libraries to be run
 123   for every dynamic object loaded by an executable - provided that the loader
 124   supports this functionality.
 125
 126 * Tighten linker script grammar around file name specifiers to prevent the use
 127   of SORT_BY_ALIGNMENT and SORT_BY_INIT_PRIORITY on filenames.  These would
 128   previously be accepted but had no effect.
 129
 130 * The EXCLUDE_FILE directive can now be placed within any SORT_* directive
 131   within input section lists.
 132
 133 Changes in 2.29:
 134
 135 * Support for -z shstk in the x86 ELF linker to generate
 136   GNU_PROPERTY_X86_FEATURE_1_SHSTK in ELF GNU program properties.
 137
 138 * Add support for GNU_PROPERTY_X86_FEATURE_1_SHSTK in ELF GNU program
 139   properties in the x86 ELF linker.
 140
 141 * Add support for GNU_PROPERTY_X86_FEATURE_1_IBT in ELF GNU program
 142   properties in the x86 ELF linker.
 143
 144 * Support for -z ibtplt in the x86 ELF linker to generate IBT-enabled
 145   PLT.
 146
 147 * Support for -z ibt in the x86 ELF linker to generate IBT-enabled
 148   PLT as well as GNU_PROPERTY_X86_FEATURE_1_IBT in ELF GNU program
 149   properties.
 150
 151 * Add support for ELF SHF_GNU_MBIND and PT_GNU_MBIND_XXX.
 152
 153 * Add support for ELF GNU program properties.
 154
 155 * Add support for the Texas Instruments PRU processor.
 156
 157 * When configuring for arc*-*-linux* targets the default linker emulation will
 158   change if --with-cpu=nps400 is used at configure time.
 159
 160 * Improve assignment of LMAs to orphan sections in some edge cases where a
 161   mixture of both AT>LMA_REGION and AT(LMA) are used.
 162
 163 * Orphan sections placed after an empty section that has an AT(LMA) will now
 164   take an load memory address starting from LMA.
 165
 166 * Section groups can now be resolved (the group deleted and the group members
 167   placed like normal sections) at partial link time either using the new linker
 168   option --force-group-allocation or by placing FORCE_GROUP_ALLOCATION into the
 169   linker script.
 170
 171 Changes in 2.28:
 172
 173 * The EXCLUDE_FILE linker script construct can now be applied outside of the
 174   section list in order for the exclusions to apply over all input sections in
 175   the list.
 176
 177 * Add support for the RISC-V architecture.
 178
 179 * The command-line option --no-eh-frame-hdr can now be used in ELF based
 180   linkers to disable the automatic generation of .eh_frame_hdr sections.
 181
 182 * Add --in-implib=<infile> to the ARM linker to enable specifying a set of
 183   Secure Gateway veneers that must exist in the output import library specified
 184   by --out-implib=<outfile> and the address they must have.  As such,
 185   --in-implib is only supported in combination with --cmse-implib.
 186
 187 * Extended the --out-implib=<file> option, previously restricted to x86 PE
 188   targets, to any ELF based target.  This allows the generation of an import
 189   library for an ELF executable, which can then be used by another application
 190   to link against the executable.
 191
 192 Changes in 2.27:
 193
 194 * Add a configure option --enable-relro to decide whether -z relro should
 195   be enabled in ELF linker by default.  Default to yes for all Linux
 196   targets except FRV, HPPA, IA64 and MIPS.  Note that -z relro can increase
 197   disk and memory size.
 198
 199 * Support for -z noreloc-overflow in the x86-64 ELF linker to disable
 200   relocation overflow check.
 201
 202 * Add -z common/-z nocommon options for ELF targets to control whether to
 203   convert common symbols to the STT_COMMON type during a relocatable link.
 204
 205 * Support for -z nodynamic-undefined-weak in the x86 ELF linker, which
 206   avoids dynamic relocations against undefined weak symbols in executable.
 207
 208 * The NOCROSSREFSTO command was added to the linker script language.
 209
 210 * Add --no-apply-dynamic-relocs to the AArch64 linker to do not apply link-time
 211   values for dynamic relocations.
 212
 213 Changes in 2.26:
 214
 215 * Add --fix-stm32l4xx-629360 to the ARM linker to enable a link-time
 216   workaround for a bug in the bus matrix / memory controller for some of
 217   the STM32 Cortex-M4 based products (STM32L4xx)
 218
 219 * Add a configure option --enable-compressed-debug-sections={all,ld} to
 220   decide whether DWARF debug sections should be compressed by default.
 221
 222 * Add support for the ARC EM/HS, and ARC600/700 architectures.
 223
 224 * Experimental support for linker garbage collection (--gc-sections)
 225   has been enabled for COFF and PE based targets.
 226
 227 * New command-line option for ELF targets to compress DWARF debug
 228   sections, --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi].
 229
 230 * New command-line option, --orphan-handling=[place|warn|error|discard], to
 231   adjust how orphan sections are handled.  The default is 'place' which gives
 232   the current behaviour, 'warn' and 'error' issue a warning or error
 233   respectively when orphan sections are found, and 'discard' will discard all
 234   orphan sections.
 235
 236 * Add support for LLVM plugin.
 237
 238 * Add --print-memory-usage option to report memory blocks usage.
 239
 240 * Add --require-defined option, it's like --undefined except the new symbol
 241   must be defined by the end of the link.
 242
 243 Changes in 2.25:
 244
 245 * PE binaries now once again contain real timestamps by default.  To disable
 246   the inclusion of a timestamp in a PE binary, use the --no-insert-timestamp
 247   command-line option.
 248
 249 * Replace support for openrisc and or32 with support for or1k.
 250
 251 * Add support for the --build-id command-line option to COFF based targets.
 252
 253 * x86/x86_64 pe-coff now supports the --build-id option.
 254
 255 * Add support for the Andes NDS32.
 256
 257 Changes in 2.24:
 258
 259 * Add LOG2CEIL() builtin function to the linker script language
 260
 261 * Add support for the Texas Instruments MSP430X processor.
 262
 263 * Add support for Altera Nios II.
 264
 265 * Add support for the V850E3V5 architecture.
 266
 267 * Add support for the Imagination Technologies Meta processor.
 268
 269 * --enable-new-dtags no longer generates old dtags in addition to new dtags.
 270
 271 * Remove linker support for MIPS ECOFF targets.
 272
 273 * Add ALIGN_WITH_INPUT to the linker script language to force the alignment of
 274   an output section to use the maximum alignment of all its input sections.
 275
 276 Changes in 2.23:
 277
 278 * Enable compressed debug section feature for x86/x86_64 pe-coff.
 279
 280 * Add support for the 64-bit ARM architecture: AArch64.
 281
 282 * Added SORT_NONE to the linker script language to disable section sorting.
 283
 284 * Add a linker-provided symbol when producing ELF output, '__ehdr_start'
 285   to point to the ELF file header (and nearby program headers) in the
 286   program's memory image.
 287
 288 * Add support for S12X processor.
 289
 290 * Add support for the VLE extension to the PowerPC architecture.
 291
 292 * Add support for the Freescale XGATE architecture.
 293
 294 * Add option -f FILE on AIX (for response file).
 295
 296 * Add support for the Renesas RL78 architecture.
 297
 298 * Add support for the Adapteva EPIPHANY architecture.
 299
 300 Changes in 2.22:
 301
 302 * --copy-dt-needed-entries is no longer enabled by default.  Instead
 303   --no-copy-dt-needed-entries is the default.
 304
 305 * INPUT_SECTION_FLAGS has been added to the linker script language
 306   to allow selection of input sections by section header section flags.
 307
 308 * Add support for the Tilera TILEPro and TILE-Gx architectures.
 309
 310 * Added SORT_BY_INIT_PRIORITY to the linker script language to permit
 311   sorting sections by numerical value of the GCC init_priority attribute
 312   encoded in the section name.
 313
 314 Changes in 2.21:
 315
 316 * Linker script expression evaluation is somewhat more sane.  This may
 317   break scripts that depend on quirks of the old expression evaluation.
 318
 319 * Turn off underscoring for x86_64 PE+-COFF targets.  For old behavior the
 320   option --enable-leading-mingw64-underscores can be used on configure of
 321   bfd.
 322
 323 * Add support for the TMS320C6000 (TI C6X) processor family.
 324
 325 * --add-needed renamed to --copy-dt-needed-entries in order to avoid confusion
 326   with --as-needed option.
 327
 328 * Extend .def file syntax by '== <ID>' for imports and exports. This allows
 329   to alias the import/export table name written in PE image.
 330
 331 * Add --exclude-all-symbols option to PE based linkers.  This prevents all
 332   symbols from automatically being exported.
 333
 334 * Add support for the Renesas RX processor.
 335
 336 * Add support for alpha-vms target.
 337
 338 Changes in 2.20:
 339
 340 * GNU/Linux targets now support the STB_GNU_UNIQUE symbol binding.  This is a
 341   GNU extension to the standard set of ELF symbol bindings.  The binding will
 342   be passed on to the dynamic linker which will make sure that in the entire
 343   process there is just one symbol with the given name and type in use.
 344
 345 * PE targets now support a GNU extension to allow the alignment of common
 346   common symbols to be specified.  This support uses custom options in
 347   the .drectve section, which will be disregarded by the native tools.
 348
 349 * PE targets now add primitive support for ELF version scripts; symbols
 350   are not versioned, but the local and global symbol visibility directives
 351   are respected when filtering symbols in auto-export mode.
 352
 353 * New option --no-export-dynamic to undo the effect of the -E and
 354   --export-dynamic options.
 355
 356 * ELF: --warn-alternate-em option to warn if an object has alternate
 357   ELF machine code.
 358
 359 * New script function REGION_ALIAS to add alias names to memory regions.
 360
 361 * PE targets no longer make use of the long section names PE extension to
 362   the COFF format when generating executable images, by default.  The old
 363   (slightly non-conformant) behaviour can still be invoked by using the
 364   new '--enable-long-section-names' command-line option.  It is also enabled
 365   automatically in the presence of un-stripped debug information, as GDB
 366   needs to be able to find the debug info sections by their full names.
 367
 368 * For GNU/Linux systems the linker will now avoid processing any relocations
 369   made against symbols of the STT_GNU_IFUNC type and instead emit them into
 370   the resulting binary for processing by the loader.
 371
 372 * --as-needed now links in a dynamic library if it satisfies undefined
 373   symbols in regular objects, or in other dynamic libraries.  In the
 374   latter case the library is not linked if it is found in a DT_NEEDED
 375   entry of one of the libraries already linked.
 376
 377 * Add a new command-line option, -Ttext-segment ADDR, for ELF targets
 378   to set the address of the first byte of the text segment.
 379
 380 * Add support for Sunplus score architecture.
 381
 382 * Add new option --use-nul-prefixed-import-tables to ld for PE targets to
 383   allow fallback to old import table generation with null element prefix.
 384
 385 * Windows PE systems now support a new --exclude-modules-for-implib option,
 386   allowing users to partition object files and archive members between a DLL
 387   and its associated import library as they are generated during linking.
 388
 389 * Add support for Lattice Mico32 (lm32) architecture.
 390
 391 * Add CR16 ELF --embedded-relocs (used to embedded relocations into binaries
 392   for Embedded-PIC code) option.
 393
 394 * Add to the PE/PE+ targets the support of two different kinds of
 395   pseudo-relocations.  They can be selected by the switches
 396   --enable-runtime-pseudo-reloc-v1 and --enable-runtime-pseudo-reloc-v2.
 397   For the switch --enable-runtime-pseudo-reloc it uses for 32-bit
 398   runtime pseudo relocation version one, for 64-bit the version two.
 399
 400 Changes in 2.19:
 401
 402 * Linker scripts support a new INSERT command that makes it easier to
 403   augment the default script.
 404
 405 * Linker script input section filespecs may now specify a file within an
 406   archive by writing "archive:file".
 407
 408 * The --sort-common switch now has an optional argument which specifies the
 409   direction of sorting.
 410
 411 * The M68K linker now supports multiple GOT generation schemes controlled via
 412   the --got=<type> command-line option.
 413
 414 * The ARM EABI linker will now generate stubs for function calls to symbols
 415   that are too far away.  The placement of the stubs is controlled by a new
 416   linker command-line option: --stub-group-size=N.
 417
 418 Changes in 2.18:
 419
 420 * Linker sources now released under version 3 of the GNU General Public
 421   License.
 422
 423 * ELF: New --build-id option to generate a unique per-binary identifier
 424   embedded in a note section.
 425
 426 * Added support for National Semicondutor CompactRISC (ie CR16) target.
 427
 428 * -l:foo now searches the library path for a filename called foo,
 429   without converting it to libfoo.a or libfoo.so.
 430
 431 * Add a new command-line option '--default-script=FILE' or '-dT FILE'
 432   which specifies a replacement for the built in, default linker
 433   script.
 434
 435 * ELF: Add -Bsymbolic-functions, --dynamic-list-cpp-new, which puts C++
 436   operator new and delete on the dynamic list, and --dynamic-list-data,
 437   builtin list for --dynamic-list, which puts global data symbols on the
 438   dynamic list.
 439
 440 * Add support for x86_64 PE+ target.
 441
 442 * Add support for Score target.
 443
 444 * ELF: Add --dynamic-list option to specify a list of global symbols
 445   whose references shouldn't be bound to the definition within the
 446   shared library, or a list of symbols which should be added to the
 447   symbol table in the executable.
 448
 449 * The default output section LMA has changed for allocatable sections from
 450   being equal to VMA, to keeping the difference between LMA and VMA the same as
 451   the previous output section in the same region.  This is a more useful
 452   default when using overlays and other cases where you specify an LMA
 453   differing from the VMA for some sections.
 454
 455 * New switch: --print-gc-sections to list any sections removed by garabge
 456   collection.
 457
 458 * ARM: Added --vfp11-denorm-fix option to work around an erratum in current
 459   VFP11 coprocessors.
 460
 461 Changes in 2.17:
 462
 463 * Support for the Infineon XC16X has been added by KPIT Cummins Infosystems.
 464
 465 * Modify the Linux linker search order to better match ld.so search order.
 466   Look for DT_NEEDED libraries in paths specified by ld.so.conf before
 467   searching the default directories, rather than vice versa.
 468   Use $prefix/etc/ld.so.conf if it exists, otherwise /etc/ld.so.conf.
 469
 470 * PE-COFF: Forward exports from DLL's can now be specified in .def files
 471   passed directly to ld.
 472
 473 * Support for the Z80 processor family has been added.
 474
 475 * Add support for the "@<file>" syntax to the command line, so that extra
 476   switches can be read from <file>.
 477
 478 Changes in 2.16:
 479
 480 * Support for the R_ARM_V4BX relocation as defined in the ARM AAELF
 481   specification has been added via the --fix-v4bx command-line option.
 482
 483 * New linker script construct AS_NEEDED(), which sets the --as-needed flag
 484   for input files listed inside of it.
 485
 486 * A new command-line option, --sysroot, can be used to override the
 487   default sysroot location.  It only applies to toolchains that were
 488   configured using --with-sysroot.
 489
 490 * New linker script functions: ORIGIN() and LENGTH() which return information
 491   about a specified memory region.
 492
 493 * Port to MAXQ processor contributed by HCL Tech.
 494
 495 * Added SEGMENT_START to the linker script language to permit the user to
 496   override the base address for a segment from the command-line.
 497
 498 * ELF: --warn-shared-textrel option to warn if adding a DT_TEXTREL to a shared
 499   object.
 500
 501 * Added SORT_BY_NAME and SORT_BY_ALIGNMENT to the linker script
 502   language to permit sorting sections by section name or section
 503   maximum alignment.
 504
 505 * Added a new linker command-line switch, --sort-section name|alignment,
 506   to sort sections by section name or maximum alignment.
 507
 508 * ELF: --add-needed/--no-add-needed options to control if a DT_NEEDED tag
 509   should be added when a shared library comes from DT_NEEDED tags.
 510
 511 * Support for the crx-elf target added.
 512
 513 * Support for the sh-symbianelf target added.
 514
 515 * A new linker command-line switch has been added which allows the hash table
 516   size to be set to a suitable prime value near to its argument.  This switch
 517   is --hash-size=<NUMBER>.  Also if the switch --reduce-memory-overheads is
 518   used, and --hash-size has not been used, then the default value will be set
 519   to 1021.
 520
 521 * Linker map files are now generated with an O(N) algorithm for finding symbols
 522   that are defined in each section.  This uses about 40% more memory for
 523   symbols than the old O(N^2) algorithm.  You can use the new
 524   --reduce-memory-overheads option to select the old algorithm; this option
 525   might also be used in the future to select similar tradeoffs.
 526
 527 Changes in 2.15:
 528
 529 * ELF: --as-needed/--no-as-needed options to control if a DT_NEEDED tag should
 530   be added only when a shared library is referenced.
 531
 532 * PE: --large-address-aware option to indicate executables support virtual
 533   addresses greater than 2 gigabytes.
 534
 535 * DWARF 2 support for i386pe added.
 536
 537 * The linker script operator DEFINED() will now yield 1 only for a symbol that
 538   is defined before the statement where DEFINED is used.
 539
 540 * The MIPS --embedded-relocs (used to embed relocations into binaries for
 541   Embedded-PIC code) is deprecated and will be removed in a future release.
 542
 543 * cr16c support added by NSC.
 544
 545 * m32r Linux (ELF) support added by Renesas.
 546
 547 * Improved linker's handling of unresolved symbols.  The switch
 548   --unresolved-symbols=<method> has been added to tell the linker when it
 549   should report them and the switch --warn-unresolved-symbols has been added to
 550   make reports be issued as warning messages rather than errors.
 551
 552 Changes in 2.14:
 553
 554 * Added support for Xtensa architecture.
 555
 556 * Added --with-sysroot configure switch to specify a target system root, for
 557   linking against a target filesystem image.
 558
 559 * Added --accept-unknown-linker-format to restore old linker behaviour (pre
 560   2.14) of silently accepting and linking in any files in an unknown binary
 561   file format.
 562
 563 * Added --no-omagic to undo the effects of the -N option.
 564
 565 * Support for Texas Instruments TMS320C4x and TMS320C3x series of
 566   DSP's contributed by Michael Hayes and Svein E. Seldal.
 567
 568 * Added --with-lib-path configure switch to specify default value for
 569   LIB_PATH.
 570
 571 * ARM port to QNX operating system added by Graeme Peterson.
 572
 573 * IP2K support added by Denis Chertykov.
 574
 575 Changes in 2.13:
 576
 577 * Support for the Fujitsu FRV architecture added by Red Hat. Models for FR400
 578   and FR500 included.
 579
 580 Changes in version 2.13:
 581
 582 * DEC VAX ELF support, by Matt Thomas.
 583
 584 Changes in version 2.12:
 585
 586 * Support for Don Knuth's MMIX, by Hans-Peter Nilsson.
 587
 588 * Support for the OpenRISC 32-bit embedded processor by OpenCores.
 589
 590 * Support for -z nocopyreloc in the x86 ELF linker, which disables
 591   production of copy relocs.  Warning: using this option may result in
 592   non-sharable applications.
 593
 594 * Support for -z combreloc in the ELF linker, which puts dynamic
 595   relocations against the same symbol together, so that dynamic linker
 596   can use an one-entry symbol lookup cache.
 597
 598 * Support for ELF SHF_MERGE section merging, by Jakub Jelinek.
 599
 600 Changes in version 2.11:
 601
 602 * Support for AMD x86-64 architecture, by Jan Hubicka, SuSE Labs.
 603
 604 * Support added for eliminating duplicate DWARF2 debug information by
 605   having the compiler generate the information in sections called
 606   .gnu.linkonce.wi.XXXX where XXXX is a checksum for the contents.  The
 607   linker then merges these sections together into the normal .debug_info
 608   section.
 609
 610 * The native ELF linker now searches the directories in DT_RUNPATH or
 611   DT_RPATH of a shared library for shared libraries needed by it.
 612
 613 * TI C54x support, by Timothy Wall.
 614
 615 * Added command-line switch --section-start to set the start address of any
 616   specified section.
 617
 618 * Added ability to emit full relocation information in linked executables,
 619   enabled by --emit-relocs.  Some post-linkage optimization tools need
 620   this information in order to be able to correctly identify and perform
 621   symbol relative addressing in the event of changes in section contents
 622   (instructions being added or deleted, extending data sections, etc.)
 623
 624 * Support for i860, by Jason Eckhardt (preliminary, alpha quality).
 625
 626 * Support for CRIS (Axis Communications ETRAX series).
 627
 628 * Support for PDP-11 and 2.11BSD a.out format, by Lars Brinkhoff.
 629
 630 Changes in version 2.10:
 631
 632 * Added AT> to the linker script language to allow load-time allocation of
 633   sections into regions.
 634
 635 * Added garbage collection of unused sections, enabled by --gc-sections.
 636   It does require a bit of backend support; currently implemented are
 637   arm-elf, avr-elf, d10v-elf, fr30-elf, i386-elf, m32r-elf, m68k-elf,
 638   mcore-elf, mips-elf, mn10300-elf, ppc-elf, sh-elf, sparc-elf, and v850-elf.
 639   Others will ignore the option.
 640
 641 * Added SORT to the linker script language to permit sorting sections by file
 642   name or section name.
 643
 644 * Added EXTERN to the linker script language as an equivalent to the -u
 645   command-line option.
 646
 647 * Added ASSERT to the linker script language.
 648
 649 * Added EXCLUDE_FILE to the linker script language for further control over
 650   wildcard file names.
 651
 652 * Added -O option to optimize linker output (as of this writing, this only
 653   affects ELF shared library generation).
 654
 655 * The -e option now accepts a number as well as a symbol name.
 656
 657 * Added --no-undefined option to disallow undefined symbols when creating a
 658   shared library.
 659
 660 * The linker now issues a warning, not an error, for an undefined symbol when
 661   using -Bsymbolic; use the new --no-undefined option to get the old
 662   behaviour.
 663
 664 * Added --demangle and --no-demangle options.
 665
 666 Changes in version 2.9:
 667
 668 * Added SQUAD to the linker script language.
 669
 670 * New option --no-warn-mismatch.
 671
 672 * The MEMORY command now parses the attributes to determine where sections that
 673   are not placed in a specific memory region are placed.
 674
 675 Changes in version 2.8:
 676
 677 * Linker scripts may now contain shell wildcard characters for file and section
 678   names.
 679
 680 * The linker now supports symbol versions in ELF.
 681
 682 * The NOCROSSREFS command was added to the linker script language.
 683
 684 * The LOADADDR expression was added to the linker script language.
 685
 686 * MAX and MIN functions were added to the linker script language.
 687
 688 * The OVERLAY construct was added to the linker script language.
 689
 690 * New option --warn-section-align to warn when the address of an output section
 691   changes due to alignment of an input section.
 692
 693 * New options --filter/-F and --auxiliary/-f.
 694
 695 Changes in version 2.7:
 696
 697 * New option --cref to print out a cross reference table.
 698
 699 * New option --wrap SYMBOL.
 700
 701 * New option --no-whole-archive, to turn off the effect of --whole-archive.
 702
 703 * Input sections assigned to the output section /DISCARD/ in the linker script
 704   are not included in the output file.
 705
 706 * The SunOS and ELF linkers now merge stabs debugging information which uses
 707   the N_BINCL and N_EINCL stab types.  This reduces the amount of debugging
 708   information generated.
 709
 710 Changes in version 2.6:
 711
 712 * When an ELF section name is representable as a C identifier (this is not true
 713 of most ELF section names), the linker will automatically define symbols
 714 __start_SECNAME and __stop_SECNAME, where SECNAME is the section name, at the
 715 beginning and the end of the section.  This is used by glibc.
 716
 717   Addendum: Current versions of the linker (at least for version 2.18 onwards
 718 and possibly much earlier as well) place two restrictions on this feature:  The
 719 symbols are only implemented for orphaned sections, not for explicitly placed
 720 sections and they are PROVIDEd rather than being defined.
 721
 722 * When an ELF section named .gnu.warning is encountered in an input file, the
 723 contents of the section are displayed as an error message, and the section is
 724 not copied into the output file.  This is used by glibc.
 725
 726 * When an ELF section named .gnu.warning.SYMBOL is encountered in an input
 727 file, and the symbol SYMBOL is referenced by some object file, the contents of
 728 the section are displayed as an error message.  The section is not copied into
 729 the output file, unless doing a relocatable or shared link.  This is used by
 730 glibc.
 731
 732 * New options -split-by-reloc and -split-by-file.
 733
 734 * The linker now supports linking PIC compiled code on SPARC SunOS.  It can
 735 also create SPARC SunOS shared libraries, and, like the native SunOS linker,
 736 will do so whenever there is an undefined symbol in the link and neither the -e
 737 nor the -r option was used.
 738
 739 * The -rpath option may be used on SunOS to set the list of directories to be
 740 searched at run time.  This overrides the default of building the list from the
 741 -L options.
 742
 743 * The COFF linker now combines debugging information for structs, unions, and
 744 enums, so that even if the same type is defined in multiple input files it will
 745 only be defined once in the output file.  The --traditional-format switch will
 746 prevent this optimization.
 747
 748 Changes in version 2.5:
 749
 750 * The linker now supports linking against SunOS shared libraries.  It still can
 751 not link SunOS PIC (Position Independent Code) files, so it can not be used to
 752 generate shared libraries.
 753
 754 * The linker now supports linking against ELF shared libraries for the i386
 755 (UnixWare) and SPARC (Solaris).  It can also link ELF PIC files, and can be
 756 used to generate shared libraries.  Shared library generation is not well
 757 tested; please report any problems encountered.  The linker is now enabled for
 758 Solaris again.
 759
 760 * Eric Youngdale has contributed Linux support code, including linking against
 761 Linux a.out shared libraries.  The linker produces Linux QMAGIC binaries.
 762
 763 * The ELF backend has been converted to the new linker code.  To use the new
 764 ELF linker, each particular target requires a relocation function.  So far,
 765 this function has been written for i386 (UnixWare), SPARC (Solaris) MIPS (Irix
 766 5), and HPPA ELF targets.
 767
 768 * The -( (--start-group) and -) (--end-group) options have been added to
 769 support searching a group of archives as though they were a single archive.
 770 This can also be used in a linker script, as GROUP ( files ).
 771
 772 * When a file is named on the command line, and the linker does not recognize
 773 it as an object file, the linker will now treat the file as a linker script
 774 file.  A linker script named in this way augments, but does not replace, the
 775 default linker script.
 776
 777 * The -warn-once option was added.  It causes the linker to only warn once per
 778 undefined symbol, rather than once per reference.
 779
 780 * The COFF backend has been converted to the new linker code.  As with ELF, to
 781 use the new linker, each particular target requires a relocation function.  So
 782 far, this function has been written for the i386, m68k, a29k and SH targets.
 783
 784 * The -V flag was made a synonym for -v, for SVR4 compatibility.  The old -V
 785 behaviour is available via --verbose.
 786
 787 Changes in version 2.4:
 788
 789 * New linker code, by Steve Chamberlain and Ian Taylor.  For a.out and ecoff
 790   formats (so far), this should result in considerable savings in time
 791   and memory used while linking; slightly poorer performance than
 792   before for formats not converted yet.
 793
 794 * Command-line parsing is no longer done with flex.  This means
 795   oddball characters in filenames won't get treated as argument
 796   separators.
 797
 798 * HP-PA ELF support, by Jeff Law.  (No SOM support yet.)
 799
 800 * Mach i386 support, by David Mackenzie.
 801
 802 * Irix 4 shared libraries are now supported (Irix 5 uses ELF, and ELF shared
 803   libraries are not yet supported).
 804
 805 * COFF shared libraries (as on SCO) should work as well.
 806
 807 * The linker is disabled for Solaris.  (Actually, it was in 2.3 also, I just
 808   forgot to note it.)  Some of their C library routines don't work when
 809   statically linked, and the GNU linker doesn't support dynamic linking yet.
 810
 811 Changes in version 2.3:
 812
 813 * Weak symbols are now supported.
 814
 815 * ELF support has been added.  The linker has been bootstrapped on
 816   UnixWare and Solaris.
 817
 818 * Alpha OSF/1 support has been added (non dynamic linking only).
 819
 820 Changes in version 2.2:
 821
 822 * The `bfd' library has been updated to reduce a.out-format string
 823   table size.  The effect of this is that files linked from many input
 824   files with duplicate symbols (`-g' debugging records, or identical
 825   static symbols) should be much smaller.
 826
 827 Changes in version 2.1:
 828
 829 * The ld -ySYMBOL flag (to trace references to SYMBOL) is now implemented.
 830
 831 * There is now support for writing ECOFF files, so ld and the
 832   other utilities should work on Risc/Ultrix and Irix.
 833
 834 \f
 835 Copyright (C) 2012-2020 Free Software Foundation, Inc.
 836
 837 Copying and distribution of this file, with or without modification,
 838 are permitted in any medium without royalty provided the copyright
 839 notice and this notice are preserved.
 840
 841 Local variables:
 842 fill-column: 79
 843 End: