mold 1.2.0

mold 1.2.0 is a new release of the high-speed linker. The highlight of this release is the 32-bit ARM support. We also added other features, and as always, we fixed many bugs and compatibility issues in this release.

New features

• The ARM32 target is now supported.
• --gdb-index is implemented. If this option is given, mold creates an .gdb_index section in an output file to speed up GNU debugger. Users have to compile their object files with -ggnu-pubnames to use this flag. mold used to ignore --gdb-index. (a7475dd)
• mold now supports the following flags: --start-address, -Tbss, -Tdata, -Ttext, --oformat=binary, --disable-new-dtags

Deprecated features

• An experimental, mold-specific --preload flag has been marked as deprecated. It's still usable, but a warning message will be displayed if that flag is given.

Bug fixes and compatibility improvements

• -dy and -dn are now accepted as aliases for -Bdynamic and -Bstatic, respectively. (82e8072)
• -static-pie now works with older versions of glibc thanks to a few bug fixes. (3d68824, 0884f27)
• Issues found by UndefinedBehaviorSanizer, AddressSanitizer and ThreadSanitizer are fixed. (bf26753, f4753b3, e1e4e9f)
• mold used to place sections with very large section alignment requirements to wrong places in an output file. That caused a mysterious crash of a produced binary (#405). That bug was most noticeable when Nvidia-provided object files are given because they tend to contain such sections. This bug has been fixed. (100922b)
• .ctors and .dtors sections are now recognized by mold, and their contents are sorted with a special rule. This shouldn't affect most build environments because these sections have been superseded by .init_array and .fini_array sections a long time ago. But it looks like some old i386 compilers are still using .ctors and .dtors. (392781a)
• For a non-position-independent executable, we have to make address-taken PLT entries as "canonical". Marking all PLT entries canonical should be harmless in theory, so we did so. However, some programs, notably Qt library, assume that non-address-taken PLTs can never be canonical (#352). For the sake of compatibility with such programs, we now make PLTs canonical only when their addresses are taken. (e0bc74a)
• mold now defines _TLS_MODULE_BASE_ symbol. A reference to this symbol can occur if -mtls-dialect=gnu2 is given to a compiler. The flag tells the compiler to use TLSDESC mechanism instead of the regular TLS access mechanism to access thread-local variables. (5feab82)
• libbacktrace sometimes fail to read compressed debug sections in mold-generated files due to a bug. We not only fix that libbacktrace's bug (ianlancetaylor/libbacktrace#87) but also implemented a workaround to mold (ba63479) so that mold works with older versions of libbacktrace.
• [ARM64] mold now recognizes R_AARCH64_LD_PREL_LO19 relocation. (146ddd7)
• [RISCV64] The correct semantics of R_RISCV_ALIGN is implemented. (0daf623)