ldc-developers/ldc v1.27.0

LDC 1.27.0

on GitHub

(Changes since 1.27.0-beta3 are marked with (new).)

Big news

• Frontend, druntime and Phobos are at version 2.097.1+. (#3741, #3770, #3771, #3790, #3794, #3796, #3799) (new)
• LLVM for prebuilt packages bumped to v12.0.1, and Linux base image to Ubuntu 18.04. Unfortunately, the dynamic-compile (JIT) functionality is lost this way - it needs some more work to adapt to a newer LLVM API. (#3701, #3789)
• Prebuilt packages now bundle reggae, a meta build tool to generate ninja/make build files for dub projects (and more). Building large projects with many dependencies can be significantly sped-up via parallelization and dependency tracking for incremental builds. (#3739)
  Basic usage, in a dub project dir (containing a dub.{sdl,json} file):

  reggae -b ninja|make --dc=ldc2   # only needed the first time or when adding source files
  ninja|make [-j<N>]
  

• Greatly improved DLL support on Windows, making it almost as easy as on Posix:
  • -fvisibility=public now also affects Windows, exporting all defined symbols as on Posix, without explicit export visibility. Compiling a DLL with -shared now defaults to -fvisibility=public for consistency with Posix. (#3703)
  • This paved the way for druntime and Phobos DLLs, now bundled with prebuilt Windows packages and linkable via -link-defaultlib-shared (default with -shared, consistent with Posix targets). Previous hacks to partially accomodate for multiple, statically linked druntimes and Phobos in a single process (GC proxy etc.) aren't required any longer. With -link-defaultlib-shared, LDC now defaults to -mscrtlib=msvcrt, linking against the shared MSVC runtime. (ldc-developers/druntime#197, #3704, ldc-developers/druntime#198)
  • Limitation: TLS variables cannot be accessed directly across DLL boundaries. This can be worked around with an accessor function, e.g., ldc-developers/druntime@5d3e21a35d.
  • Non-TLS extern(D) global variables not defined in a root module are dllimported (with -fvisibility=public, or - restricted to druntime/Phobos symbols - with -link-defaultlib-shared). Compiling all modules of a DLL at once thus avoids linker warnings about 'importing locally defined symbol'. When linking a DLL against a static library, the static library may likely need to be compiled with -fvisibility=public to make its globals importable from the DLL. There's a new -dllimport option for explicit control. (#3763)
  • Caveat: symbols aren't uniqued across the whole process, so can be defined in multiple DLLs/executables, each with their own address, so you cannot rely on TypeInfos, instantiated symbols and functions to have the same address for the whole process.
  • When linking manually (not via LDC), binaries linked against druntime DLL need to include new lib\dso_windows.obj.
  • To restore the previous behavior of -shared, add -fvisibility=hidden -link-defaultlib-shared=false.
• Windows: ANSI color codes can now be enforced for redirected stderr via -enable-color. (#3744)
• Prebuilt Linux and Mac packages now use the mimalloc allocator, significantly increasing compiler performance in some cases. (#3758, #3759)
• The prebuilt macOS x64 package now bundles shared druntime/Phobos libs for iOS too. (#3764)
• Possibly more performant shared Phobos library by compiling to a single object file with implicit cross-module inlining. (#3757)
• New -cov-increment option for more performant coverage count execution. (#3724)
• -fsanitize=memory: Bundle according LLVM compiler-rt library and add new -fsanitize-memory-track-origins option. (#3751)
• New LDC-specific language addition: __traits(initSymbol, <aggregate type>) with semantics equivalent to TypeInfo.initializer(), but circumventing the TypeInfo indirection and thus e.g. also usable for -betterC code. (#3774, ldc-developers/druntime#201)

Platform support

• Supports LLVM 6.0 - 12.0.

Bug fixes

• Fix debuginfo source file paths, e.g., including directories in exception stack traces. (#3687)
• Fix potentially corrupt context pointers for nested functions with -linkonce-templates. (#3690, #3766)
• Predefine version CppRuntime_Gcc for musl targets. (#3769)
• RVO: In-place construct <temporary>.__ctor(<args>). (#3778, #3779)
• -linkonce-templates: Make sure special struct TypeInfo members are semantically analyzed before emitting the TypeInfo. (#3783)

Known issues

• When building LDC, old LDC 0.17.*/ltsmaster host compilers miscompile LDC ≥ 1.21, leading to potential segfaults of the built LDC. Ltsmaster can still be used to bootstrap a first compiler and then let that compiler compile itself. (#3354)
• Buggy older ld.bfd linker versions may wrongly strip out required symbols, e.g., ModuleInfos (so that e.g. no module ctors/dtors are run). LDC defaults to ld.gold on Linux.
• LDC does not zero the padding area of a real variable. This may lead to wrong results if the padding area is also considered. See #770. Does not apply to real members inside structs etc.