lld 10.0.0 Release Notes

Introduction

This document contains the release notes for the lld linker, release 10.0.0. 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.

Non-comprehensive list of changes in this release

ELF Improvements

• Glob pattern, which you can use in linker scripts or version scripts, now supports ` and `[!...]. Except character classes (e.g. [[:digit:]]), lld's glob pattern should be fully compatible with GNU now. (r375051)
• New elf32btsmipn32_fbsd and elf32ltsmipn32_fbsd emulations are supported.
• Relax MIPS jalr and jr instructions marked by the R_MIPS_JALR relocation.
• For certain "undefined symbol" errors, a definition with a close spelling will be suggested. (D67039)
• extern "C" is suggested if an undefined reference is mangled(unmangled) while there is a likely unmangled(mangled) definition. (D69592 D69650)
• New -z noseparate-code, -z separate-code and -z separate-loadable-segments. -z noseparate-code is the default, which can reduce sizes of linked binaries by up to 3 times maxpagesize. (D64903 D67481)
• -z force-bti and -z pac-plt are added for AArch64 Branch Target Identification and Pointer Authentication. (D62609)
• --fix-cortex-a8 is added to fix erratum 657417. (D67284)
• -z force-ibt and -z shstk are added for Intel Control-flow Enforcement Technology. (D59780)
• PT_GNU_PROPERTY is added to help loaders locate the .note.gnu.property section. It may be used by a future Linux kernel. (D70961)
• For --compress-debug-sections=zlib, -O0 and -O1 enable compression level 1 while -O2 enables compression level 6. -O1 (default) is faster than before. (D70658)
• Range extension thunks with addends are implemented for AArch64, PowerPC32 and PowerPC64. (D70637 D70937 D73424)
• R_RISCV_ALIGN will be errored because linker relaxation for RISC-V is not supported. Pass -mno-relax to disable R_RISCV_ALIGN. (D71820)
• The ARM port will no longer insert interworking thunks for non STT_FUNC symbols. (D73474)
• The quality of PowerPC32 port has been greatly improved (canonical PLT, copy relocations, non-preemptible IFUNC, range extension thunks with addends). It can link FreeBSD 13.0 userland.
• The PowerPC64 port supports non-preemptible IFUNC. (D71509)
• lld creates a RO PT_LOAD and a RX PT_LOAD without a linker script. lld creates a unified RX PT_LOAD with a linker script. A future release will eliminate this difference and use a RO PT_LOAD and a RX PT_LOAD by default. The linker script case will require --no-rosegment to restore the current behavior.
• GNU style compressed debug sections .zdebug (obsoleted by SHF_COMPRESSED) are supported for input files, but not for the output. A future release may drop .zdebug support.

Breaking changes

• -Ttext=$base (base is usually 0) is no longer supported. If PT_PHDR is needed, use --image-base=$base instead. If PT_PHDR is not needed, use a linker script with .text 0 : { *(.text*) } as the first output section description. See https://bugs.llvm.org/show_bug.cgi?id=44715 for more information. (D67325)
• -Ttext-segment is no longer supported. Its meaning was different from GNU ld's and could cause subtle bugs. (D70468)

MinGW Improvements

• Allow using custom .edata sections from input object files (for use by Wine) (dadc6f248868)
• Don't implicitly create import libraries unless requested (6540e55067e3)
• Support merging multiple resource object files (3d3a9b3b413d) and properly handle the default manifest object files that GCC can pass (d581dd501381)
• Demangle itanium symbol names in warnings/error messages (a66fc1c99f3e)
• Print source locations for undefined references and duplicate symbols, if possible (1d06d48bb346) and (b38f577c015c)
• Look for more filename patterns when resolving -l options (0226c35262df)
• Don't error out on duplicate absolute symbols with the same value (which can happen for the default-null symbol for weak symbols) (1737cc750c46)

WebAssembly Improvements

• __data_end and __heap_base are no longer exported by default, as it's best to keep them internal when possible. They can be explicitly exported with --export=__data_end and --export=__heap_base, respectively.
• wasm-ld now elides .bss sections when the memory is not imported