llvm-project/lld
Ali Tamur 783d84bb39 [llvm] Prevent duplicate files in debug line header in dwarf 5: another attempt
Another attempt to land the changes in debug line header to prevent duplicate
files in Dwarf 5. I rolled back my previous commit because of a mistake in
generating the object file in a test. Meanwhile, I addressed some offline
comments and changed the implementation; the largest difference is that
MCDwarfLineTableHeader does not keep DwarfVersion but gets it as a parameter. I
also merged the patch to fix two lld tests that will strt to fail into this
patch.

Original Commit:

https://reviews.llvm.org/D59515

Original Message:
Motivation: In previous dwarf versions, file name indexes started from 1, and
the primary source file was not explicit. Dwarf 5 standard (6.2.4) prescribes
the primary source file to be explicitly given an entry with an index number 0.

The current implementation honors the specification by just duplicating the
main source file, once with index number 0, and later maybe with another
index number. While this is compliant with the letter of the standard, the
duplication causes problems for consumers of this information such as lldb.
(Some files are duplicated, where only some of them have a line table although
all refer to the same file)

With this change, dwarf 5 debug line section files always start from 0, and
the zeroth entry is not duplicated whenever possible. This requires different
handling of dwarf 4 and dwarf 5 during generation (e.g. when a function returns
an index zero for a file name, it signals an error in dwarf 4, but not in dwarf
5) However, I think the minor complication is worth it, because it enables all
consumers (lldb, gdb, dwarfdump, objdump, and so on) to treat all files in the
file name list homogenously.

llvm-svn: 358732
2019-04-19 02:26:56 +00:00
..
COFF [LLD][COFF] use offset in archive to disambiguate archive members 2019-04-15 19:48:32 +00:00
Common Fail early if an output file is not writable 2019-03-11 16:30:55 +00:00
ELF [LLD][ELF] - A fix for "linker script assignment loses relative nature of section" bug. 2019-04-18 10:00:37 +00:00
MinGW [MinGW] Hook up the --exclude-all-symbols option 2019-02-19 21:57:49 +00:00
cmake/modules [CMake] Properly conditionalize installation of lld libraries 2018-03-09 13:09:36 +00:00
docs [COFF] Link crtend.o as the last object file 2019-04-15 10:57:44 +00:00
include/lld Fail early if an output file is not writable 2019-03-11 16:30:55 +00:00
lib lld: Fix initial Mach-O load commands size calculation omitting LC_FUNCTION_STARTS 2019-04-17 01:47:16 +00:00
test [llvm] Prevent duplicate files in debug line header in dwarf 5: another attempt 2019-04-19 02:26:56 +00:00
tools/lld Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
unittests Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
utils Python 2/3 compatibility 2019-03-20 07:42:13 +00:00
wasm [wasm] Simplify. NFC 2019-04-18 13:33:29 +00:00
.arcconfig [lld] Set up .arcconfig to point to new Diffusion LLD repository 2017-12-06 20:56:23 +00:00
.clang-format
.gitignore
CMakeLists.txt [WebAssembly] Initial wasm linker implementation 2017-11-17 18:14:09 +00:00
CODE_OWNERS.TXT [WebAssembly] Initial wasm linker implementation 2017-11-17 18:14:09 +00:00
LICENSE.TXT Fix typos throughout the license files that somehow I and my reviewers 2019-01-21 09:52:34 +00:00
README.md Note that the test .tar.xz has been updated. 2017-12-22 19:37:32 +00:00

README.md

LLVM Linker (lld)

This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.

lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.

Benchmarking

In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.

It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz

The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.