ld/NEWS

   1 -*- text -*-
   2
   3 * Add --error-handling-script=<NAME> command line option to allow a helper
   4   script to be invoked when an undefined symbol or a missing library is
   5   encountered.  This option can be suppressed via the configure time
   6   switch: --enable-error-handling-script=no.
   7
   8 * Add -z x86-64-v[234] to the x86 ELF linker to mark x86-64-v[234] ISA
   9   level as needed.
  10
  11 * Add -z unique-symbol to avoid duplicated local symbol names.
  12
  13 * The creation of PE format DLLs now defaults to using a more secure set of DLL
  14   characteristics.
  15
  16 * The linker now deduplicates the types in .ctf sections.  The new
  17   command-line option --ctf-share-types describes how to do this:
  18   its default value, share-unconflicted, produces the most compact
  19   output.
  20
  21 * The linker now omits the "variable section" from .ctf sections by
  22   default, saving space.  This is almost certainly what you want
  23   unless you are working on a project that has its own analogue
  24   of symbol tables that are not reflected in the ELF symtabs.
  25
  26 Changes in 2.35:
  27
  28 * X86 NaCl target support is removed.
  29
  30 * Add ELF linker command-line options, --export-dynamic-symbol and
  31   --export-dynamic-symbol-list, to make symbols dynamic.
  32
  33 * Add a configure option, --enable-textrel-check=[no|yes|warning|error],
  34   to decide what ELF linker should do by default with DT_TEXTREL in an
  35   executable or shared library.  Default to yes for Linux/x86 targets.
  36
  37 * The -Map=<filename> command line option has been extended so that if
  38   <filename> is a directory then <filename>/<output-filename>.map will be
  39   created.
  40
  41 * Add a command-line option for ELF linker, --warn-textrel, to warn that
  42   DT_TEXTREL is set in a position-independent executable or shared object.
  43
  44 * Add command-line options --enable-non-contiguous-regions and
  45   --enable-non-contiguous-regions-warnings.
  46
  47 * Add command-line option --imagic for the pdp11-aout target to output format
  48   IMAGIC (0411) for separate instruction and data spaces, and change the
  49   default format option for pdp11-aout to be --omagic.
  50
  51 * Relative pathnames in INPUT() and GROUP() directives in linker scripts are
  52   searched relative to the directory of the linker script before other search
  53   paths.
  54
  55 * Add ELF linker command-line option `-z start-stop-visibility=...' to control
  56   the visibility of synthetic `__start_SECNAME` and `__stop_SECNAME` symbols.
  57
  58 * Add command-line option --dependency-file to write a Make-style dependency
  59   file listing the input files consulted by the linker, like the files written
  60   by the compiler's -M -MP options.
  61
  62 Changes in 2.34:
  63
  64 * The ld check for "PHDR segment not covered by LOAD segment" is more
  65   effective, catching cases that were wrongly allowed by previous versions of
  66   ld.  If you see this error it is likely you are linking with a bad linker
  67   script or the binary you are building is not intended to be loaded by a
  68   dynamic loader.  In the latter case --no-dynamic-linker is appropriate.
  69
  70 * cr16c support removed.
  71
  72 * Add support for z80-elf.
  73
  74 * Add support for relocation of each byte or word of multibyte value to Z80
  75   targets.
  76
  77 * Add support for Zilog eZ80 (both ADL and Z80 mode) and Zilog Z180 CPUs.
  78
  79 Changes in 2.33:
  80
  81 * Add command-line option --no-print-map-discarded.
  82
  83 * The Cortex-A53 Erratum 843419 workaround now supports a choice of which
  84   workaround to use.  The option --fix-cortex-a53-843419 now takes an
  85   optional argument --fix-cortex-a53-843419[=full|adr|adrp] which can be
  86   used to force a particular workaround to be used.  See --help for AArch64
  87   for more details.
  88
  89 * Add target handlers for AArch64 for ELF GNU program properties.
  90
  91 * Add support for GNU_PROPERTY_AARCH64_FEATURE_1_BTI in ELF GNU program
  92   properties in the AArch64 ELF linker.
  93
  94 * Add support for GNU_PROPERTY_AARCH64_FEATURE_1_PAC in ELF GNU program
  95   properties in the AArch64 ELF linker.
  96
  97 * Add -z force-bti for AArch64 to enable GNU_PROPERTY_AARCH64_FEATURE_1_BTI
  98   on output while warning about missing GNU_PROPERTY_AARCH64_FEATURE_1_BTI
  99   on inputs and use PLTs protected with BTI.
 100
 101 * Add -z pac-plt for AArch64 to pick PAC enabled PLTs.
 102
 103 Changes in 2.32:
 104
 105 * Report property change in linker map file when merging GNU properties.
 106
 107 * Add support for the C-SKY processor series.
 108
 109 * -t now doesn't report members within archives, unless -t is given twice.
 110   A single -t is now more useful when generating a list of files that should be
 111   packaged for a linker bug report.  For example:
 112     gcc hello.c -save-temps -Wl,-t | xargs realpath | sort | uniq > files
 113     tar cJf test.tar.xz `cat files`
 114
 115 Changes in 2.31:
 116
 117 * Speed up direct linking with DLLs for Cygwin and Mingw targets.
 118
 119 * Add a configure option --enable-separate-code to decide whether
 120   -z separate-code should be enabled in ELF linker by default.  Default
 121   to yes for Linux/x86 targets.  Note that -z separate-code can increase
 122   disk and memory size.
 123
 124 Changes in 2.30:
 125
 126 * Add -z separate-code to generate separate code PT_LOAD segment.
 127
 128 * Add "-z undefs" command-line option as the inverse of the "-z defs" option.
 129
 130 * Add -z globalaudit command-line option to force audit libraries to be run
 131   for every dynamic object loaded by an executable - provided that the loader
 132   supports this functionality.
 133
 134 * Tighten linker script grammar around file name specifiers to prevent the use
 135   of SORT_BY_ALIGNMENT and SORT_BY_INIT_PRIORITY on filenames.  These would
 136   previously be accepted but had no effect.
 137
 138 * The EXCLUDE_FILE directive can now be placed within any SORT_* directive
 139   within input section lists.
 140
 141 Changes in 2.29:
 142
 143 * Support for -z shstk in the x86 ELF linker to generate
 144   GNU_PROPERTY_X86_FEATURE_1_SHSTK in ELF GNU program properties.
 145
 146 * Add support for GNU_PROPERTY_X86_FEATURE_1_SHSTK in ELF GNU program
 147   properties in the x86 ELF linker.
 148
 149 * Add support for GNU_PROPERTY_X86_FEATURE_1_IBT in ELF GNU program
 150   properties in the x86 ELF linker.
 151
 152 * Support for -z ibtplt in the x86 ELF linker to generate IBT-enabled
 153   PLT.
 154
 155 * Support for -z ibt in the x86 ELF linker to generate IBT-enabled
 156   PLT as well as GNU_PROPERTY_X86_FEATURE_1_IBT in ELF GNU program
 157   properties.
 158
 159 * Add support for ELF SHF_GNU_MBIND and PT_GNU_MBIND_XXX.
 160
 161 * Add support for ELF GNU program properties.
 162
 163 * Add support for the Texas Instruments PRU processor.
 164
 165 * When configuring for arc*-*-linux* targets the default linker emulation will
 166   change if --with-cpu=nps400 is used at configure time.
 167
 168 * Improve assignment of LMAs to orphan sections in some edge cases where a
 169   mixture of both AT>LMA_REGION and AT(LMA) are used.
 170
 171 * Orphan sections placed after an empty section that has an AT(LMA) will now
 172   take an load memory address starting from LMA.
 173
 174 * Section groups can now be resolved (the group deleted and the group members
 175   placed like normal sections) at partial link time either using the new linker
 176   option --force-group-allocation or by placing FORCE_GROUP_ALLOCATION into the
 177   linker script.
 178
 179 Changes in 2.28:
 180
 181 * The EXCLUDE_FILE linker script construct can now be applied outside of the
 182   section list in order for the exclusions to apply over all input sections in
 183   the list.
 184
 185 * Add support for the RISC-V architecture.
 186
 187 * The command-line option --no-eh-frame-hdr can now be used in ELF based
 188   linkers to disable the automatic generation of .eh_frame_hdr sections.
 189
 190 * Add --in-implib=<infile> to the ARM linker to enable specifying a set of
 191   Secure Gateway veneers that must exist in the output import library specified
 192   by --out-implib=<outfile> and the address they must have.  As such,
 193   --in-implib is only supported in combination with --cmse-implib.
 194
 195 * Extended the --out-implib=<file> option, previously restricted to x86 PE
 196   targets, to any ELF based target.  This allows the generation of an import
 197   library for an ELF executable, which can then be used by another application
 198   to link against the executable.
 199
 200 Changes in 2.27:
 201
 202 * Add a configure option --enable-relro to decide whether -z relro should
 203   be enabled in ELF linker by default.  Default to yes for all Linux
 204   targets except FRV, HPPA, IA64 and MIPS.  Note that -z relro can increase
 205   disk and memory size.
 206
 207 * Support for -z noreloc-overflow in the x86-64 ELF linker to disable
 208   relocation overflow check.
 209
 210 * Add -z common/-z nocommon options for ELF targets to control whether to
 211   convert common symbols to the STT_COMMON type during a relocatable link.
 212
 213 * Support for -z nodynamic-undefined-weak in the x86 ELF linker, which
 214   avoids dynamic relocations against undefined weak symbols in executable.
 215
 216 * The NOCROSSREFSTO command was added to the linker script language.
 217
 218 * Add --no-apply-dynamic-relocs to the AArch64 linker to do not apply link-time
 219   values for dynamic relocations.
 220
 221 Changes in 2.26:
 222
 223 * Add --fix-stm32l4xx-629360 to the ARM linker to enable a link-time
 224   workaround for a bug in the bus matrix / memory controller for some of
 225   the STM32 Cortex-M4 based products (STM32L4xx)
 226
 227 * Add a configure option --enable-compressed-debug-sections={all,ld} to
 228   decide whether DWARF debug sections should be compressed by default.
 229
 230 * Add support for the ARC EM/HS, and ARC600/700 architectures.
 231
 232 * Experimental support for linker garbage collection (--gc-sections)
 233   has been enabled for COFF and PE based targets.
 234
 235 * New command-line option for ELF targets to compress DWARF debug
 236   sections, --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi].
 237
 238 * New command-line option, --orphan-handling=[place|warn|error|discard], to
 239   adjust how orphan sections are handled.  The default is 'place' which gives
 240   the current behaviour, 'warn' and 'error' issue a warning or error
 241   respectively when orphan sections are found, and 'discard' will discard all
 242   orphan sections.
 243
 244 * Add support for LLVM plugin.
 245
 246 * Add --print-memory-usage option to report memory blocks usage.
 247
 248 * Add --require-defined option, it's like --undefined except the new symbol
 249   must be defined by the end of the link.
 250
 251 Changes in 2.25:
 252
 253 * PE binaries now once again contain real timestamps by default.  To disable
 254   the inclusion of a timestamp in a PE binary, use the --no-insert-timestamp
 255   command-line option.
 256
 257 * Replace support for openrisc and or32 with support for or1k.
 258
 259 * Add support for the --build-id command-line option to COFF based targets.
 260
 261 * x86/x86_64 pe-coff now supports the --build-id option.
 262
 263 * Add support for the Andes NDS32.
 264
 265 Changes in 2.24:
 266
 267 * Add LOG2CEIL() builtin function to the linker script language
 268
 269 * Add support for the Texas Instruments MSP430X processor.
 270
 271 * Add support for Altera Nios II.
 272
 273 * Add support for the V850E3V5 architecture.
 274
 275 * Add support for the Imagination Technologies Meta processor.
 276
 277 * --enable-new-dtags no longer generates old dtags in addition to new dtags.
 278
 279 * Remove linker support for MIPS ECOFF targets.
 280
 281 * Add ALIGN_WITH_INPUT to the linker script language to force the alignment of
 282   an output section to use the maximum alignment of all its input sections.
 283
 284 Changes in 2.23:
 285
 286 * Enable compressed debug section feature for x86/x86_64 pe-coff.
 287
 288 * Add support for the 64-bit ARM architecture: AArch64.
 289
 290 * Added SORT_NONE to the linker script language to disable section sorting.
 291
 292 * Add a linker-provided symbol when producing ELF output, '__ehdr_start'
 293   to point to the ELF file header (and nearby program headers) in the
 294   program's memory image.
 295
 296 * Add support for S12X processor.
 297
 298 * Add support for the VLE extension to the PowerPC architecture.
 299
 300 * Add support for the Freescale XGATE architecture.
 301
 302 * Add option -f FILE on AIX (for response file).
 303
 304 * Add support for the Renesas RL78 architecture.
 305
 306 * Add support for the Adapteva EPIPHANY architecture.
 307
 308 Changes in 2.22:
 309
 310 * --copy-dt-needed-entries is no longer enabled by default.  Instead
 311   --no-copy-dt-needed-entries is the default.
 312
 313 * INPUT_SECTION_FLAGS has been added to the linker script language
 314   to allow selection of input sections by section header section flags.
 315
 316 * Add support for the Tilera TILEPro and TILE-Gx architectures.
 317
 318 * Added SORT_BY_INIT_PRIORITY to the linker script language to permit
 319   sorting sections by numerical value of the GCC init_priority attribute
 320   encoded in the section name.
 321
 322 Changes in 2.21:
 323
 324 * Linker script expression evaluation is somewhat more sane.  This may
 325   break scripts that depend on quirks of the old expression evaluation.
 326
 327 * Turn off underscoring for x86_64 PE+-COFF targets.  For old behavior the
 328   option --enable-leading-mingw64-underscores can be used on configure of
 329   bfd.
 330
 331 * Add support for the TMS320C6000 (TI C6X) processor family.
 332
 333 * --add-needed renamed to --copy-dt-needed-entries in order to avoid confusion
 334   with --as-needed option.
 335
 336 * Extend .def file syntax by '== <ID>' for imports and exports. This allows
 337   to alias the import/export table name written in PE image.
 338
 339 * Add --exclude-all-symbols option to PE based linkers.  This prevents all
 340   symbols from automatically being exported.
 341
 342 * Add support for the Renesas RX processor.
 343
 344 * Add support for alpha-vms target.
 345
 346 Changes in 2.20:
 347
 348 * GNU/Linux targets now support the STB_GNU_UNIQUE symbol binding.  This is a
 349   GNU extension to the standard set of ELF symbol bindings.  The binding will
 350   be passed on to the dynamic linker which will make sure that in the entire
 351   process there is just one symbol with the given name and type in use.
 352
 353 * PE targets now support a GNU extension to allow the alignment of common
 354   common symbols to be specified.  This support uses custom options in
 355   the .drectve section, which will be disregarded by the native tools.
 356
 357 * PE targets now add primitive support for ELF version scripts; symbols
 358   are not versioned, but the local and global symbol visibility directives
 359   are respected when filtering symbols in auto-export mode.
 360
 361 * New option --no-export-dynamic to undo the effect of the -E and
 362   --export-dynamic options.
 363
 364 * ELF: --warn-alternate-em option to warn if an object has alternate
 365   ELF machine code.
 366
 367 * New script function REGION_ALIAS to add alias names to memory regions.
 368
 369 * PE targets no longer make use of the long section names PE extension to
 370   the COFF format when generating executable images, by default.  The old
 371   (slightly non-conformant) behaviour can still be invoked by using the
 372   new '--enable-long-section-names' command-line option.  It is also enabled
 373   automatically in the presence of un-stripped debug information, as GDB
 374   needs to be able to find the debug info sections by their full names.
 375
 376 * For GNU/Linux systems the linker will now avoid processing any relocations
 377   made against symbols of the STT_GNU_IFUNC type and instead emit them into
 378   the resulting binary for processing by the loader.
 379
 380 * --as-needed now links in a dynamic library if it satisfies undefined
 381   symbols in regular objects, or in other dynamic libraries.  In the
 382   latter case the library is not linked if it is found in a DT_NEEDED
 383   entry of one of the libraries already linked.
 384
 385 * Add a new command-line option, -Ttext-segment ADDR, for ELF targets
 386   to set the address of the first byte of the text segment.
 387
 388 * Add support for Sunplus score architecture.
 389
 390 * Add new option --use-nul-prefixed-import-tables to ld for PE targets to
 391   allow fallback to old import table generation with null element prefix.
 392
 393 * Windows PE systems now support a new --exclude-modules-for-implib option,
 394   allowing users to partition object files and archive members between a DLL
 395   and its associated import library as they are generated during linking.
 396
 397 * Add support for Lattice Mico32 (lm32) architecture.
 398
 399 * Add CR16 ELF --embedded-relocs (used to embedded relocations into binaries
 400   for Embedded-PIC code) option.
 401
 402 * Add to the PE/PE+ targets the support of two different kinds of
 403   pseudo-relocations.  They can be selected by the switches
 404   --enable-runtime-pseudo-reloc-v1 and --enable-runtime-pseudo-reloc-v2.
 405   For the switch --enable-runtime-pseudo-reloc it uses for 32-bit
 406   runtime pseudo relocation version one, for 64-bit the version two.
 407
 408 Changes in 2.19:
 409
 410 * Linker scripts support a new INSERT command that makes it easier to
 411   augment the default script.
 412
 413 * Linker script input section filespecs may now specify a file within an
 414   archive by writing "archive:file".
 415
 416 * The --sort-common switch now has an optional argument which specifies the
 417   direction of sorting.
 418
 419 * The M68K linker now supports multiple GOT generation schemes controlled via
 420   the --got=<type> command-line option.
 421
 422 * The ARM EABI linker will now generate stubs for function calls to symbols
 423   that are too far away.  The placement of the stubs is controlled by a new
 424   linker command-line option: --stub-group-size=N.
 425
 426 Changes in 2.18:
 427
 428 * Linker sources now released under version 3 of the GNU General Public
 429   License.
 430
 431 * ELF: New --build-id option to generate a unique per-binary identifier
 432   embedded in a note section.
 433
 434 * Added support for National Semicondutor CompactRISC (ie CR16) target.
 435
 436 * -l:foo now searches the library path for a filename called foo,
 437   without converting it to libfoo.a or libfoo.so.
 438
 439 * Add a new command-line option '--default-script=FILE' or '-dT FILE'
 440   which specifies a replacement for the built in, default linker
 441   script.
 442
 443 * ELF: Add -Bsymbolic-functions, --dynamic-list-cpp-new, which puts C++
 444   operator new and delete on the dynamic list, and --dynamic-list-data,
 445   builtin list for --dynamic-list, which puts global data symbols on the
 446   dynamic list.
 447
 448 * Add support for x86_64 PE+ target.
 449
 450 * Add support for Score target.
 451
 452 * ELF: Add --dynamic-list option to specify a list of global symbols
 453   whose references shouldn't be bound to the definition within the
 454   shared library, or a list of symbols which should be added to the
 455   symbol table in the executable.
 456
 457 * The default output section LMA has changed for allocatable sections from
 458   being equal to VMA, to keeping the difference between LMA and VMA the same as
 459   the previous output section in the same region.  This is a more useful
 460   default when using overlays and other cases where you specify an LMA
 461   differing from the VMA for some sections.
 462
 463 * New switch: --print-gc-sections to list any sections removed by garabge
 464   collection.
 465
 466 * ARM: Added --vfp11-denorm-fix option to work around an erratum in current
 467   VFP11 coprocessors.
 468
 469 Changes in 2.17:
 470
 471 * Support for the Infineon XC16X has been added by KPIT Cummins Infosystems.
 472
 473 * Modify the Linux linker search order to better match ld.so search order.
 474   Look for DT_NEEDED libraries in paths specified by ld.so.conf before
 475   searching the default directories, rather than vice versa.
 476   Use $prefix/etc/ld.so.conf if it exists, otherwise /etc/ld.so.conf.
 477
 478 * PE-COFF: Forward exports from DLL's can now be specified in .def files
 479   passed directly to ld.
 480
 481 * Support for the Z80 processor family has been added.
 482
 483 * Add support for the "@<file>" syntax to the command line, so that extra
 484   switches can be read from <file>.
 485
 486 Changes in 2.16:
 487
 488 * Support for the R_ARM_V4BX relocation as defined in the ARM AAELF
 489   specification has been added via the --fix-v4bx command-line option.
 490
 491 * New linker script construct AS_NEEDED(), which sets the --as-needed flag
 492   for input files listed inside of it.
 493
 494 * A new command-line option, --sysroot, can be used to override the
 495   default sysroot location.  It only applies to toolchains that were
 496   configured using --with-sysroot.
 497
 498 * New linker script functions: ORIGIN() and LENGTH() which return information
 499   about a specified memory region.
 500
 501 * Port to MAXQ processor contributed by HCL Tech.
 502
 503 * Added SEGMENT_START to the linker script language to permit the user to
 504   override the base address for a segment from the command-line.
 505
 506 * ELF: --warn-shared-textrel option to warn if adding a DT_TEXTREL to a shared
 507   object.
 508
 509 * Added SORT_BY_NAME and SORT_BY_ALIGNMENT to the linker script
 510   language to permit sorting sections by section name or section
 511   maximum alignment.
 512
 513 * Added a new linker command-line switch, --sort-section name|alignment,
 514   to sort sections by section name or maximum alignment.
 515
 516 * ELF: --add-needed/--no-add-needed options to control if a DT_NEEDED tag
 517   should be added when a shared library comes from DT_NEEDED tags.
 518
 519 * Support for the crx-elf target added.
 520
 521 * Support for the sh-symbianelf target added.
 522
 523 * A new linker command-line switch has been added which allows the hash table
 524   size to be set to a suitable prime value near to its argument.  This switch
 525   is --hash-size=<NUMBER>.  Also if the switch --reduce-memory-overheads is
 526   used, and --hash-size has not been used, then the default value will be set
 527   to 1021.
 528
 529 * Linker map files are now generated with an O(N) algorithm for finding symbols
 530   that are defined in each section.  This uses about 40% more memory for
 531   symbols than the old O(N^2) algorithm.  You can use the new
 532   --reduce-memory-overheads option to select the old algorithm; this option
 533   might also be used in the future to select similar tradeoffs.
 534
 535 Changes in 2.15:
 536
 537 * ELF: --as-needed/--no-as-needed options to control if a DT_NEEDED tag should
 538   be added only when a shared library is referenced.
 539
 540 * PE: --large-address-aware option to indicate executables support virtual
 541   addresses greater than 2 gigabytes.
 542
 543 * DWARF 2 support for i386pe added.
 544
 545 * The linker script operator DEFINED() will now yield 1 only for a symbol that
 546   is defined before the statement where DEFINED is used.
 547
 548 * The MIPS --embedded-relocs (used to embed relocations into binaries for
 549   Embedded-PIC code) is deprecated and will be removed in a future release.
 550
 551 * cr16c support added by NSC.
 552
 553 * m32r Linux (ELF) support added by Renesas.
 554
 555 * Improved linker's handling of unresolved symbols.  The switch
 556   --unresolved-symbols=<method> has been added to tell the linker when it
 557   should report them and the switch --warn-unresolved-symbols has been added to
 558   make reports be issued as warning messages rather than errors.
 559
 560 Changes in 2.14:
 561
 562 * Added support for Xtensa architecture.
 563
 564 * Added --with-sysroot configure switch to specify a target system root, for
 565   linking against a target filesystem image.
 566
 567 * Added --accept-unknown-linker-format to restore old linker behaviour (pre
 568   2.14) of silently accepting and linking in any files in an unknown binary
 569   file format.
 570
 571 * Added --no-omagic to undo the effects of the -N option.
 572
 573 * Support for Texas Instruments TMS320C4x and TMS320C3x series of
 574   DSP's contributed by Michael Hayes and Svein E. Seldal.
 575
 576 * Added --with-lib-path configure switch to specify default value for
 577   LIB_PATH.
 578
 579 * ARM port to QNX operating system added by Graeme Peterson.
 580
 581 * IP2K support added by Denis Chertykov.
 582
 583 Changes in 2.13:
 584
 585 * Support for the Fujitsu FRV architecture added by Red Hat. Models for FR400
 586   and FR500 included.
 587
 588 Changes in version 2.13:
 589
 590 * DEC VAX ELF support, by Matt Thomas.
 591
 592 Changes in version 2.12:
 593
 594 * Support for Don Knuth's MMIX, by Hans-Peter Nilsson.
 595
 596 * Support for the OpenRISC 32-bit embedded processor by OpenCores.
 597
 598 * Support for -z nocopyreloc in the x86 ELF linker, which disables
 599   production of copy relocs.  Warning: using this option may result in
 600   non-sharable applications.
 601
 602 * Support for -z combreloc in the ELF linker, which puts dynamic
 603   relocations against the same symbol together, so that dynamic linker
 604   can use an one-entry symbol lookup cache.
 605
 606 * Support for ELF SHF_MERGE section merging, by Jakub Jelinek.
 607
 608 Changes in version 2.11:
 609
 610 * Support for AMD x86-64 architecture, by Jan Hubicka, SuSE Labs.
 611
 612 * Support added for eliminating duplicate DWARF2 debug information by
 613   having the compiler generate the information in sections called
 614   .gnu.linkonce.wi.XXXX where XXXX is a checksum for the contents.  The
 615   linker then merges these sections together into the normal .debug_info
 616   section.
 617
 618 * The native ELF linker now searches the directories in DT_RUNPATH or
 619   DT_RPATH of a shared library for shared libraries needed by it.
 620
 621 * TI C54x support, by Timothy Wall.
 622
 623 * Added command-line switch --section-start to set the start address of any
 624   specified section.
 625
 626 * Added ability to emit full relocation information in linked executables,
 627   enabled by --emit-relocs.  Some post-linkage optimization tools need
 628   this information in order to be able to correctly identify and perform
 629   symbol relative addressing in the event of changes in section contents
 630   (instructions being added or deleted, extending data sections, etc.)
 631
 632 * Support for i860, by Jason Eckhardt (preliminary, alpha quality).
 633
 634 * Support for CRIS (Axis Communications ETRAX series).
 635
 636 * Support for PDP-11 and 2.11BSD a.out format, by Lars Brinkhoff.
 637
 638 Changes in version 2.10:
 639
 640 * Added AT> to the linker script language to allow load-time allocation of
 641   sections into regions.
 642
 643 * Added garbage collection of unused sections, enabled by --gc-sections.
 644   It does require a bit of backend support; currently implemented are
 645   arm-elf, avr-elf, d10v-elf, fr30-elf, i386-elf, m32r-elf, m68k-elf,
 646   mcore-elf, mips-elf, mn10300-elf, ppc-elf, sh-elf, sparc-elf, and v850-elf.
 647   Others will ignore the option.
 648
 649 * Added SORT to the linker script language to permit sorting sections by file
 650   name or section name.
 651
 652 * Added EXTERN to the linker script language as an equivalent to the -u
 653   command-line option.
 654
 655 * Added ASSERT to the linker script language.
 656
 657 * Added EXCLUDE_FILE to the linker script language for further control over
 658   wildcard file names.
 659
 660 * Added -O option to optimize linker output (as of this writing, this only
 661   affects ELF shared library generation).
 662
 663 * The -e option now accepts a number as well as a symbol name.
 664
 665 * Added --no-undefined option to disallow undefined symbols when creating a
 666   shared library.
 667
 668 * The linker now issues a warning, not an error, for an undefined symbol when
 669   using -Bsymbolic; use the new --no-undefined option to get the old
 670   behaviour.
 671
 672 * Added --demangle and --no-demangle options.
 673
 674 Changes in version 2.9:
 675
 676 * Added SQUAD to the linker script language.
 677
 678 * New option --no-warn-mismatch.
 679
 680 * The MEMORY command now parses the attributes to determine where sections that
 681   are not placed in a specific memory region are placed.
 682
 683 Changes in version 2.8:
 684
 685 * Linker scripts may now contain shell wildcard characters for file and section
 686   names.
 687
 688 * The linker now supports symbol versions in ELF.
 689
 690 * The NOCROSSREFS command was added to the linker script language.
 691
 692 * The LOADADDR expression was added to the linker script language.
 693
 694 * MAX and MIN functions were added to the linker script language.
 695
 696 * The OVERLAY construct was added to the linker script language.
 697
 698 * New option --warn-section-align to warn when the address of an output section
 699   changes due to alignment of an input section.
 700
 701 * New options --filter/-F and --auxiliary/-f.
 702
 703 Changes in version 2.7:
 704
 705 * New option --cref to print out a cross reference table.
 706
 707 * New option --wrap SYMBOL.
 708
 709 * New option --no-whole-archive, to turn off the effect of --whole-archive.
 710
 711 * Input sections assigned to the output section /DISCARD/ in the linker script
 712   are not included in the output file.
 713
 714 * The SunOS and ELF linkers now merge stabs debugging information which uses
 715   the N_BINCL and N_EINCL stab types.  This reduces the amount of debugging
 716   information generated.
 717
 718 Changes in version 2.6:
 719
 720 * When an ELF section name is representable as a C identifier (this is not true
 721 of most ELF section names), the linker will automatically define symbols
 722 __start_SECNAME and __stop_SECNAME, where SECNAME is the section name, at the
 723 beginning and the end of the section.  This is used by glibc.
 724
 725   Addendum: Current versions of the linker (at least for version 2.18 onwards
 726 and possibly much earlier as well) place two restrictions on this feature:  The
 727 symbols are only implemented for orphaned sections, not for explicitly placed
 728 sections and they are PROVIDEd rather than being defined.
 729
 730 * When an ELF section named .gnu.warning is encountered in an input file, the
 731 contents of the section are displayed as an error message, and the section is
 732 not copied into the output file.  This is used by glibc.
 733
 734 * When an ELF section named .gnu.warning.SYMBOL is encountered in an input
 735 file, and the symbol SYMBOL is referenced by some object file, the contents of
 736 the section are displayed as an error message.  The section is not copied into
 737 the output file, unless doing a relocatable or shared link.  This is used by
 738 glibc.
 739
 740 * New options -split-by-reloc and -split-by-file.
 741
 742 * The linker now supports linking PIC compiled code on SPARC SunOS.  It can
 743 also create SPARC SunOS shared libraries, and, like the native SunOS linker,
 744 will do so whenever there is an undefined symbol in the link and neither the -e
 745 nor the -r option was used.
 746
 747 * The -rpath option may be used on SunOS to set the list of directories to be
 748 searched at run time.  This overrides the default of building the list from the
 749 -L options.
 750
 751 * The COFF linker now combines debugging information for structs, unions, and
 752 enums, so that even if the same type is defined in multiple input files it will
 753 only be defined once in the output file.  The --traditional-format switch will
 754 prevent this optimization.
 755
 756 Changes in version 2.5:
 757
 758 * The linker now supports linking against SunOS shared libraries.  It still can
 759 not link SunOS PIC (Position Independent Code) files, so it can not be used to
 760 generate shared libraries.
 761
 762 * The linker now supports linking against ELF shared libraries for the i386
 763 (UnixWare) and SPARC (Solaris).  It can also link ELF PIC files, and can be
 764 used to generate shared libraries.  Shared library generation is not well
 765 tested; please report any problems encountered.  The linker is now enabled for
 766 Solaris again.
 767
 768 * Eric Youngdale has contributed Linux support code, including linking against
 769 Linux a.out shared libraries.  The linker produces Linux QMAGIC binaries.
 770
 771 * The ELF backend has been converted to the new linker code.  To use the new
 772 ELF linker, each particular target requires a relocation function.  So far,
 773 this function has been written for i386 (UnixWare), SPARC (Solaris) MIPS (Irix
 774 5), and HPPA ELF targets.
 775
 776 * The -( (--start-group) and -) (--end-group) options have been added to
 777 support searching a group of archives as though they were a single archive.
 778 This can also be used in a linker script, as GROUP ( files ).
 779
 780 * When a file is named on the command line, and the linker does not recognize
 781 it as an object file, the linker will now treat the file as a linker script
 782 file.  A linker script named in this way augments, but does not replace, the
 783 default linker script.
 784
 785 * The -warn-once option was added.  It causes the linker to only warn once per
 786 undefined symbol, rather than once per reference.
 787
 788 * The COFF backend has been converted to the new linker code.  As with ELF, to
 789 use the new linker, each particular target requires a relocation function.  So
 790 far, this function has been written for the i386, m68k, a29k and SH targets.
 791
 792 * The -V flag was made a synonym for -v, for SVR4 compatibility.  The old -V
 793 behaviour is available via --verbose.
 794
 795 Changes in version 2.4:
 796
 797 * New linker code, by Steve Chamberlain and Ian Taylor.  For a.out and ecoff
 798   formats (so far), this should result in considerable savings in time
 799   and memory used while linking; slightly poorer performance than
 800   before for formats not converted yet.
 801
 802 * Command-line parsing is no longer done with flex.  This means
 803   oddball characters in filenames won't get treated as argument
 804   separators.
 805
 806 * HP-PA ELF support, by Jeff Law.  (No SOM support yet.)
 807
 808 * Mach i386 support, by David Mackenzie.
 809
 810 * Irix 4 shared libraries are now supported (Irix 5 uses ELF, and ELF shared
 811   libraries are not yet supported).
 812
 813 * COFF shared libraries (as on SCO) should work as well.
 814
 815 * The linker is disabled for Solaris.  (Actually, it was in 2.3 also, I just
 816   forgot to note it.)  Some of their C library routines don't work when
 817   statically linked, and the GNU linker doesn't support dynamic linking yet.
 818
 819 Changes in version 2.3:
 820
 821 * Weak symbols are now supported.
 822
 823 * ELF support has been added.  The linker has been bootstrapped on
 824   UnixWare and Solaris.
 825
 826 * Alpha OSF/1 support has been added (non dynamic linking only).
 827
 828 Changes in version 2.2:
 829
 830 * The `bfd' library has been updated to reduce a.out-format string
 831   table size.  The effect of this is that files linked from many input
 832   files with duplicate symbols (`-g' debugging records, or identical
 833   static symbols) should be much smaller.
 834
 835 Changes in version 2.1:
 836
 837 * The ld -ySYMBOL flag (to trace references to SYMBOL) is now implemented.
 838
 839 * There is now support for writing ECOFF files, so ld and the
 840   other utilities should work on Risc/Ultrix and Irix.
 841
 842 \f
 843 Copyright (C) 2012-2020 Free Software Foundation, Inc.
 844
 845 Copying and distribution of this file, with or without modification,
 846 are permitted in any medium without royalty provided the copyright
 847 notice and this notice are preserved.
 848
 849 Local variables:
 850 fill-column: 79
 851 End: