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mold 1.5.0
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@rui314 rui314 released this 27 Sep 06:29
· 1827 commits to main since this release
v1.5.0
95ad47c

mold 1.5.0 is a new release of the high-speed linker. The highlight of this release is that we start supporting the following four new targets: PPC64LE, SPARC64, RV32BE and RV64BE. mold 1.5.0 also includes various bug fixes, performance and compatibility improvements as shown below.

Starting from this release, we recommend using cmake instead of make to build mold. We will soon stop supporting make, so please migrate early and report issues if you find any.

Note for those who create mold binary packages: if you are building mold for binary distribution, please link the bundled libtbb statically (which is default) or rebuild your distro's libtbb package with my patch so that mold's Link-Time Optimization (LTO) works reliably under heavy load.

New features

  • PPC64LE and SPARC64 are now supported as new targets. They haven't yet been as well tested as other targets, but they are already able to link mold itself on these platforms. (Note that PPC64LE is very unlikely to work on the most recent POWER10 machines as we didn't have a chance to test it due to a limited availability (POWER10 was released in 2021). If you can support us on this matter, please contact us. We also accept donations, so please consider supporting our project!)
  • RV32BE and RV64BE (32-bit and 64-bit big-endian RISC-V) are now supported as experimental targets. RISC-V is usually little-endian, but there exists a big-endian RISC-V as an extension. You can make gcc to emit code for big-endian RISC-V by passing -mbig-endian. mold can now link object files generated with that option.
  • --compress-debug-sections=zstd is now supported. This is an option to compress debug info embedded to an output file with Zstandard compression algorithm. Compared to the existing --compress-debug-sections=zlib, zstd is faster and gives a higher compression ratio. You probably can't start using zstd compression today though, because other tools such as gdb may not be able to read zstd-compressed debug info yet. But adding this option early makes mold future-proof. (ede7a5a)
  • mold no longer aligns loadable segments to page boundaries to reduce output file size. Previously, we allocated holes between loadable segments. The saving by this change is most visible for small programs. For example, a "hello world" program used to be ~18 KiB on x86-64. It's now 7.2 KiB. (2941d75)

Bug fixes and compatibility improvements

  • [RISCV] We optimized code so that the link speed for RISC-V is now comparable to the other targets. As an example, linking mold itself (~150 MiB in size) for RV64 used to take ~45 seconds on a simulated 16-core machine. It now takes only ~0.25 seconds. (3ab5489)
  • mold used to create more than one .rodata section under a certain condition. It's not technically wrong but confused Valgrind. This issue has been resolved. (25c7aee)
  • [ARM32] Previously, mold failed to promote remaining undefined symbols to dynamic symbols if symbols are undefined weak. That caused a link failure for libxml (#660). This issue has been resolved. (72e26d9)
  • mold didn't copy symbol types when creating symbol aliases for the --defsym option. (8c7f31c)

Removed features

  • --compress-debug-sections=zlib-gnu has been removed. LLVM lld removed that option too as there seems to be no usage of the flag.

Acknowledgements

mold is an open-source project, and we accept donations via GitHub Sponsors and OpenCollective. We thank you to everybody who sponsors our project. In particular, we'd like to acknowledge the following organizations and people who have sponsored $32/mo or more during this release cycle:

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