[lld] r308700 - Add contents to lld 5.0's release notes.

Fri Jul 21 12:26:52 PDT 2017

Thanks!
Rui Ueyama via llvm-commits <llvm-commits at lists.llvm.org> writes:

> Author: ruiu
> Date: Thu Jul 20 17:28:02 2017
> New Revision: 308700
>
> URL: http://llvm.org/viewvc/llvm-project?rev=308700&view=rev
> Log:
> Add contents to lld 5.0's release notes.
>
> Modified:
>     lld/branches/release_50/docs/ReleaseNotes.rst
>
> Modified: lld/branches/release_50/docs/ReleaseNotes.rst
> URL: http://llvm.org/viewvc/llvm-project/lld/branches/release_50/docs/ReleaseNotes.rst?rev=308700&r1=308699&r2=308700&view=diff
> ==============================================================================
> --- lld/branches/release_50/docs/ReleaseNotes.rst (original)
> +++ lld/branches/release_50/docs/ReleaseNotes.rst Thu Jul 20 17:28:02 2017
> @@ -1,5 +1,5 @@
>  =======================
> -LLD 5.0.0 Release Notes
> +lld 5.0.0 Release Notes
>  =======================
>  
>  .. contents::
> @@ -13,9 +13,9 @@ LLD 5.0.0 Release Notes
>  Introduction
>  ============
>  
> -This document contains the release notes for the LLD linker, release 5.0.0.
> -Here we describe the status of LLD, including major improvements
> -from the previous release. All LLD releases may be downloaded
> +This document contains the release notes for the lld linker, release 5.0.0.
> +Here we describe the status of lld, including major improvements
> +from the previous release. All lld releases may be downloaded
>  from the `LLVM releases web site <http://llvm.org/releases/>`_.
>  
>  Non-comprehensive list of changes in this release
> @@ -24,7 +24,78 @@ Non-comprehensive list of changes in thi
>  ELF Improvements
>  ----------------
>  
> -* Item 1.
> +* First and foremost, a lot of compatibility issues and bugs has been fixed.
> +  Linker script support has significantly improved. As a result, we believe you
> +  are very likely to be able to link your programs with lld without experiencing
> +  any problem now.
> +
> +* Error message format has changed in order to improve readability.
> +  Traditionally, linker's error messages are concise and arguably too tarse.
> +  This is an example of lld 4.0's error message (they are actually in one line)::
> +
> +    /ssd/clang/bin/ld.lld: error: /ssd/llvm-project/lld/ELF/Writer.cpp:207:
> +      undefined symbol 'lld::elf::EhFrameSection::addSection()'
> +
> +  It is not easy to read because too many information is packed into single line
> +  and the embedded text, particularly a symbol name, is sometimes too long.
> +  In lld 5.0, we use more vertical space to print out error messages in a more
> +  structured manner like this::
> +
> +    bin/ld.lld: error: undefined symbol: lld::elf::EhFrameSection::addSection()
> +    >>> Referenced by Writer.cpp:207 (/ssd/llvm-project/lld/ELF/Writer.cpp:207)
> +    >>>               Writer.cpp.o in archive lib/liblldELF.a
> +
> +  As a bonus, the new error message contains source code location of the error
> +  if it is available from debug info.
> +
> +* ``./configure`` scripts generated by GNU autoconf determines wheter a linker
> +  supports modern GNU-compatible features or not by searching for "GNU" in the
> +  ``--help`` message. To be compatible with the scripts, we decided to add a
> +  string "(compatible with GNU linkers)" to our ``--help`` message. This is a
> +  hack, but just like the web browser's User-Agent string, we had no choice
> +  other than doing this to declare that we accept GNU-compatible options.
> +
> +* The ``-Map`` option is added. The option is to make the linker to print out how
> +  input files are mapped to the output file. Here is an example::
> +
> +    Address          Size             Align Out     In      Symbol
> +    00000000016d84d8 00000000008f8f50     8 .eh_frame
> +    00000000016d84d8 00000000008f8f50     8         <internal>:(.eh_frame)
> +    0000000001fd2000 00000000034b3bd0    16 .text
> +    0000000001fd2000 000000000000002a     1         /usr/lib/x86_64-linux-gnu/crt1.o:(.text)
> +    0000000001fd2000 0000000000000000     0                 _start
> +    0000000001fd202a 0000000000000000     1         /usr/lib/x86_64-linux-gnu/crti.o:(.text)
> +    0000000001fd2030 00000000000000bd    16         /usr/lib/gcc/x86_64-linux-gnu/4.8/crtbegin.o:(.text)
> +    0000000001fd2030 0000000000000000     0                 deregister_tm_clones
> +    0000000001fd2060 0000000000000000     0                 register_tm_clones
> +
> +  This format is not the same as GNU linkers as our linker internal data
> +  structure is different from them but contains the same amount of information
> +  and should be more readable than their outputs.
> +
> +  As with other lld features, the ``-Map`` option is desigend with speed in mind.
> +  The option would generate a hundred megabyte of text file if you link a large
> +  program with it. lld can usually do that in a few seconds, and it is generally
> +  a few times faster than the GNU gold's ``-Map`` option.
> +
> +* Some nonstandard relocations, such as R_X86_64_8 or R_X86_64_16, are supported.
> +  They are not used for 32/64-bit applications, but some 16-bit bootloaders need
> +  them.
> +
> +* Paddings in executable text sections are now filled with trap instructions
> +  (such as INT3) instead of being left as null bytes. This change improves
> +  disassembler outputs because it now prints out trap instructions instead of
> +  trying to decode 0x00 as an instruction. It also makes debugging of some type
> +  of program easier because when the control reaches a padding, the program
> +  immediately raises an error.
> +
> +* The following options are added: ``-M``, ``-Map``,
> +  ``-compress-debug-sections``, ``-emit-relocs``,
> +  ``-error-unresolved-symbols``, ``-exclude-libs``, ``-filter``,
> +  ``-no-dynamic-linker``, ``-no-export-dynamic``, ``-no-fatal-warnings``,
> +  ``-print-map``, ``-warn-unresolved-symbols``, ``-z nocopyreloc``,
> +  ``-z notext``, ``-z rodynamic``
> +
>  
>  COFF Improvements
>  -----------------
>
>
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