Go 1.13

New escape analysis on by default. Stack-allocated defer records. Background scavenger. Go 2 number literals and signed shift counts. Spec-compliant package init order. sync.Pool victim cache. internal/reflectlite.

Each area lists the stage every thread reached in this release (with what was left open afterwards), then changes that are not part of a thread. Thread names link to the full thread on its topic page.

Memory management

From Memory management: GC and allocator (Go 1.0–1.17)

Background scavenger, first-fit address-ordered allocation, huge-page-aware scavenging, effective GOGC.

• GC pacer: trigger controller, assists and background utilisation — Done: effective GOGC and no GOGC in minimum sweep distance (5c22842cf2, 4a7d5aa30b, 7da03b9fbb). Left open: nothing noted.
• Stack scanning: conservative, precise by frames, stack barriers, hybrid barrier, async safe points — Done: gp._panic, defer closure scanned (af8f4062c2, 4f4c2a79d4) with clobberfree; stack freeing separated from shrinking (68d89bb8e0). Left open: nothing noted.
• Size classes, tiny allocator and mcache/mcentral — Done: division → multiply/shift (6ca51f7897). Left open: nothing noted.
• Span lifecycle in mheap: free lists, treaps, first-fit and the page reclaimer — Done: first-fit, unified treap, in-place split, filtered iteration, treap iterator conversions (40036a99a0, 8c05d67661, 9baa4301cf, 5c15ed64de, fa8470a8cd, 7bb8fc1033, 7b33b6274f, a62b5723be, f4a5ae5594, ff70494b75). Left open: the heap lock held for all span operations, and a tree allocator that would not scale: replaced in 1.14.
• Scavenger: returning memory to the OS — Done: background scavenger and removal of periodic scavenger (fe67ea32bf, eaa1c87b00), huge-page-aware (a62b5723be, 31c4e09915, 8c3040d768, f4a5ae5594, ff70494b75, 4e7bef84c1 newly mapped memory is marked scavenged because on most OSs untouched pages are not resident). Left open: scavenging pacing relied on estimates; 1.14 made it self-paced.
• Heap address space: contiguous arena to sparse arenas — Done: wasm memory handling (460f9c6068 optimise memory allocation on wasm, c2d9eea1f1 no arena hints on wasm), sbrk alignment (5b15510d96), first persistentalloc chunk aligned (c5babcc485). Left open: nothing noted.
• Allocation-site profiling and GC debugging modes — Done: clobberfree (af8f4062c2). Left open: nothing noted.

Other changes

• Misc internal — latent TODOs resolved (9c86eae384), debugging prints removed (12e63226b9), scavenge-in-coalescing guard (2ab6d0172e), scavengeLargest merge (23d4c6cdd6), heap lock stack growth invariant (7ed7669c0d).

Scheduler and concurrency

From Scheduler and concurrency runtime (Go 1.0–1.17)

Pool victim cache and lock-free queues, inlinable sync fast paths, preemption on many short syscalls, poller error reporting; threads: Pool, Mutex, preemption.

• The G-M-P scheduler: from global-lock M:N to per-P run queues, spinning Ms and work stealing — Done: look for an idle P when switching to a GC worker or trace reader e56c73f17b; initP/destroyP split out of procresize 9d088fbfda; switch to P0 before destroying current P 4598c23c6c; acquirem/releasem used more widely ea9859f858; P statuses documented b0c6165605.
• Preemption: cooperative stack-check preemption (1.2) to signal-based asynchronous preemption (1.14) — Done: user-visible a goroutine that runs many short syscalls is now preempted (the 10ms rule did not cover them) 4166ff42c0.
• Network poller: from the netFD select loop to the runtime-integrated epoll/kqueue/IOCP poller — Done: user-visible event-scanning errors reported on read events a5fdd58c84, narrowed to critical errors only 451a2eb0ab, disabled on Solaris e0181ff52a.
• Semaphores, runtime locks and Notes — Done: AIX noteclear 1956b28ae3; notetsleep sanity check ac40a7fb9e; js/wasm lock implementation cd03664f82.
• sync.Mutex, RWMutex, WaitGroup, Cond, Once — Done: inlinable fast paths (above).
• sync.Pool — Done: lock-free queues 2b60567002, 57bb7be4b1, d5fd2dd6a1, victim cache 2dcbf8b369.
• Fast random numbers for the scheduler — Done: randomized package initialization order in race mode 8515d9cf65.

Other changes

• Misc internal — eaa1c87b00 (periodic scavenging removed), d016330241 (debugCall whitelisting), 98c5a56f01, 7a43f8a5fb, 480df2c2b4, db42bb3b70, 0188cb0e8a, f448c212a1, ad832284c7, b51c157025, bc593eac2d, 91c385b393, 29f14f058d.

Data structures and type metadata

From Runtime data structures and type metadata (Go 1.0–1.17)

internal/reflectlite, reflect.IsZero, ifaceeq direct fast path, kindNoPointers removed, StructOf GC fixes, arm bytealg.

• Hash map core: from the first hashmap.c to the 8-entry bucket design — Done: “key”/“element” terminology applied across the implementation (73cb9a1cb3).
• Compiler-generated equality and hash functions — Done: argument array no longer noalg (343b7fa626).
• Runtime type descriptors: layout, shrinking and name encoding — Done: kindNoPointers removed (db16de9203).
• Interface values, itabs and type assertions — Done: ifaceeq direct fast path (694cd005c3), fun[0] only on success (8d86ef2216).
• reflect dynamic types: ArrayOf, ChanOf, MapOf, SliceOf, FuncOf, StructOf — Done: StructOf GC program fixes (05b3db24c1, 9dc3b8b722, 17f888c5a8).
• reflect.Call, MakeFunc, method values and argument-frame GC precision — Done: MakeFunc assignment conversion of returned values and better panic for Value{} (fe83731651, 04845fe78a), callMethod aligns first argument (5f45a3337e).
• reflect performance, caches and API additions — Done: IsZero (c40bffd905), inlinable mustBe* (788e038e5d), method sets documented sorted (f33b67b870).
• internal/bytealg and string/byte comparison primitives — Done: arm word-wise Compare/Equal, shared code, Count (029a5af6a1, a734601bdf, 14a58d65e3, 3496ff1d19, 3cb1e9d98a), simplified Equal (ca0c449a6b), wasm memchr (4a7cd9d9df).
• internal/reflectlite and checkptr — Done: reflectlite (9650726e79, 39a51a4b0d), context deps (88adc33827, 724a86fced).

Other changes

• Misc internal — shift masks (7b62e984d9), loop simplifications (49662bc6b0), s390x build (40657c282d), deterministic anonymous interface output (fbde753a58).

Diagnostics and knobs

From Diagnostics and knobs (Go 1.0–1.17)

Runtime dlog ring-buffer debug log; go env -w/-u; arm/mips CPU profile corruption fixed.

• Race detector integration — Done: arm64 uses raceprocctx (6e37e3a80b).
• CPU profiler and runtime/pprof writers (legacy format to compressed protobuf) — Done: CPU profile corruption on arm/mips fixed — lost atomic64 count was racy (91c385b393). Left open: nothing noted.
• Profile labels — Done: heritability of labels documented (0ca4f6be35, 9a71015860 “documents labels bug”).
• GODEBUG, runtime/debug, debug log and traceback knobs — Done: binary ring-buffer debug log dlog per-M, compiled only with the debuglog build tag, printed on panic (3ebb1ad9cd); TLS 1.3 GODEBUG documented (48bb611667); user-visible go env -w/-u for persistent environment (f0e9754696). Left open: “decoding from a core dump hasn’t been implemented” (3ebb1ad9cd).

Other changes

• Misc internal — idiomatic swapping (342764a216), “Deprecated:” spelling (9a0a150c9f).

OS layer, stacks and panics

From OS interface, stacks and panics (Go 1.5–1.17)

aix/ppc64 completed, netbsd/openbsd arm64, illumos, TOPFRAME, PCDATA/FUNCDATA re-ordering, Android TLS offset made dynamic, physHugePageSize.

• New and ported OS/arch targets, 1.5–1.17 — Done: aix/ppc64 completion (c1e2227505, 8bad008cf5, 53d859bdf5, 0cd74d1f11, bf103723f8, b5cf035d1c, 38dc177d3a, 3aacfce6cf, 4e2b4d7fb2, cbaa8e5f93, 8c7564dead, d5014ec05b, b2453c0588), netbsd/arm64 (d23cba683e, 37133b5d63), openbsd/arm64 (3d94dd78d4, 17a7f21790, 08b956f378, 998cc2a1c5), illumos split from solaris (f686a2890b), dynamic Android TLS offset (1d10b17589, 95f18757a0, f18c31a49c, eddb41eb2c).
• Goroutine stack growth, shrinking, GC stack barriers and stack objects — Done: stack freeing separated from shrinking (68d89bb8e0), m.libcallsp check now panics, one lock per stackpool order.
• Tracebacks, symbol tables and runtime.Callers/CallersFrames — Done: TOPFRAME on goexit (aafe257390), PCDATA/FUNCDATA reordering (4aeac68c92), lazy file/line in Frames.Next (c77a9e0aa5), dumpgoroutine follow-ups in 1.14.
• Signals: masks, forwarding, sigaltstack and the unified Unix signal layer — Done: sigpipe check fix (0c75eb824c), darwin signal wake-up via a pipe (c485e8b559), sigtramp callee-saved registers on arm64/arm Darwin (cbdf9ade56, df901bce5e), sigfwd and sigtramp on AIX (bf103723f8, b5cf035d1c).
• cgo runtime support: pointer checks, callbacks, extra Ms, C-to-Go call path — Done: Windows _cgo_sys_thread_create calling convention (bec67e1130), Android threadentry unification (b2f19dad8b), cgo_wait_runtime_init_done prototype (9586c093a2), AIX asmcgocall ABI (c1e2227505).
• Shared-library and buildmode entry points (c-archive, c-shared, plugin, shared) — Done: aix/ppc64 library startup and c-archive (38dc177d3a, 3aacfce6cf).
• vDSO, time sources and process-wide randomness — Done: setNsec for timespec (0a7bc8f430), NetBSD/amd64 timespec fix (ee551846fa).
• Darwin and OpenBSD move to libc; Solaris and AIX libcall; syscall wrapper layer — Done: 9da6530faa, 85d56c3096, c485e8b559, d410642f49, 7d65e3a853, abf8e355a8, c00ff65d01 (default system stack size on non-cgo macOS), f6b42a53e5/d32ec38f1c DNS via libSystem (internal, then removed).
• Windows runtime — Done: safe DLL loading (9b6e9f0c8c), NewCallback returns all bits (5cf4e442a5), windows-amd64-2012 build (ef4666ecce).
• CPU feature detection (internal/cpu), auxv parsing and GODEBUG=cpu.* — Done: s390x API alignment and new ECDSA/EDDSA caps (1f17d61026, ba978f5fff), remove FreeBSD workarounds (3b6216ed06), physHugePageSize (1033065ee3, 7fcba81549), openbsd/arm64 HWCap (08b956f378).
• Assembly-level runtime entry points: memequal/cmp/IndexByte, hashing, atomics and ABI wrappers — Done: Load8 (4a4e05b0b1), wasm StorepNoWB (814c97b313), s390x StorepNoWB (13b7c04d3f), ABI0 atomic wrappers (62c309c54c, 82521659de), Loadp noescape (9dce58d30d), bounds-check regs on arm (689544c0b9), wasm write barrier (d9db9e32e9), mark Go symbols called from asm (f5e5bc1a42), tidy asm (ee1c76dccd, 26a5f6a32e, 064ce85c20), getg in preinit on Android (ae85ae5db2).
• Debugger function calls and conservative preemption frames — Done: whitelisting debugCall32..65536 (d016330241).
• Thread lifecycle, physical page size and scheduler-facing OS hooks — Done: physHugePageSize (1033065ee3, 7fcba81549), hw.ncpuonline (c55eeeb718 in 1.16), MADV_FREE_REUSABLE (abf8e355a8).

Other changes

• Linux, vDSO, time and auxv internal — user-visible runtime: simplify readUnaligned (3aa7bbdbcb); user-visible runtime: move linux specific code into linux specific files (78f0de10ec); user-visible runtime: fix data sizes for res_search results (1fd1408203)
• other runtime/OS plumbing internal — all: join a few chained ifs (340129e4c8); all: s/cancelation/cancellation/ (5781df421e)
• cgo and C interop internal — runtime/cgo: look for android_get_device_api_level in libc.so (fc7ac2e8c0); runtime/cgo: declare variable setg_gcc as static (4312a18b8a); runtime/cgo: ignore missing Info.plist files on iOS (6ee8324388); runtime/cgo: on Solaris link against -lxnet (295419d0b4)
• BSD, Solaris, AIX, Plan 9, NaCl internal — user-visible runtime: use named macros on NetBSD (d1f43ccef7); user-visible runtime: remove spurious register loads for openbsd/amd64 kqueue (6b692300a1)
• Darwin/iOS internal — user-visible runtime: implement pthread functions for darwin/arm64 (9f12e2e04b)

Compiler frontend

From Compiler frontend (Go 1.10–1.17)

Go 2 number literals and signed shifts, evconst consolidation, spec-compliant package init order, multi-value f(g()) rewriting moved to typecheck, -newescape default.

• dev.regabi: from *Node struct to the ir.Node interface and concrete node types — Done: ORESULT added and OINDREGSP removed (336f951b07); nodl/newnamel take named fields (e92853523d, 24a6478be3). Left open: nothing noted.
• Indexed export format and the export-data lifecycle — Done: export of rewritten f(g()) calls fixed (916e861fd9); alias export metadata fix (2d357d8da8). Left open: nothing noted.
• The syntax package: parser, scanner, source reader, positions and error recovery — Done: scanner accepts Go 2 number literals via a liberal grammar (ceb849dd97, see constants thread); recovery after := in declarations (4145c5da1f); unread of more than one rune (58365b34bb). Left open: nothing noted.
• Constants: Go 2 number literals, evconst, untyped conversion and go/constant — Done: user-visible new number literals ceb849dd97, 4ad5537bfa, signed shift counts 585c9e8412, and -lang gating (762953be28); evconst consolidation 3def15cd20. Left open: nothing noted.
• Language version gating (-lang) and language changes implemented in the frontend — Done: user-visible go1.13 features guarded by -lang (762953be28); internal/goversion introduced (64e29f94e2). Left open: nothing noted.
• Package initialization order, static initialisation and init functions — Done: user-visible spec-compliant init order 5d0d87ae16; incremental map init ee59c06acb; sinit as methods (ee2836048c, d23bf3daa9); isStaticCompositeLiteral fix (004fb5cb8d); static entries of slices (a9e107c85c). Left open: nothing noted.
• Concurrent compilation and frontend performance — Done: -smallframes 037ac2bd84. Left open: nothing noted.
• Directives and pragmas in the frontend (//go: handling) — Done: dde7c770ef. Left open: nothing noted.
• The legacy typechecker: error quality, alias/recursive-type handling and type checking order — Done: dc0388c565, 4145c5da1f, 60736733ec, 6d781decad, bea58ef352. Left open: nothing noted.
• Lowering in order/walk and the shape of runtime calls emitted by the frontend — Done: d96b7fbf98/c0cfe9687f, 23b476a3c8, 1e58bb1491. Left open: nothing noted.

Other changes

• -newescape default internal — 996a687ebb makes the new escape analysis the default; a152dd0438 respects it in genwrapper.
• internal/race, -allabis removal internal — 4ee4607c97, 74d92db8d7.
• Capture-by-reference fixes and ordering internal — 94a9dad8fd, 913d290402, 644543dd64.
• Misc fixes internal — 9f6b21caea (invalid float/complex constant ops), 5fc55b3180 (type descriptor names for anonymous interfaces with unexported methods in different packages were identical and got unified by the linker), 68a98d5279, 24513d33b1, 2d7cb295fd, d41a0a0690, 53deb81219.

Middle end and SSA optimizer

From Middle end and SSA optimizer (Go 1.10–1.17)

The new escape analysis (escape.go) landed and became the default; defer records moved to the stack; signed divisibility rules and prove learned extensions/bounds facts; the rulegen rewrite began and short-circuiting/&& ordering were fixed (threads: Escape, Defers, Prove, Arithmetic, Walk/order).

• Prove pass: unsatisfiability, partial-order facts, loop bounds-check elimination — Done: poset used for non-negatives (ddef157813), repeated zero-constant checks short-cut (576442b27b), index >= 0 learned from bounds checks (2d41444ad0), induction detection for unrolled loops (d8f60eea64), int64(uint64>>x) >= 0 (66f5d4e035), slice bounds checks reversed so the RHS of IsSliceInBounds is non-negative (83a33d3855), range analysis of small signed ints fixed (f44404ebbf). Left open: extension handling (done in 1.14).
• Escape analysis: the esc.go fixes, the escape.go rewrite, and the move to package escape — Done: user-visible new escape analysis implementation added (97c4ad4327) and enabled by default (996a687ebb); CONVIFACE data flows to heap (0349f29a55); parameter tagging refactor (23bf6af996^1.14); -newescape respected in genwrapper (a152dd0438). Left open: -m=2 diagnostics and performance work (done in 1.14).
• Inlining: budget, mid-stack inlining, closures, and what became inlinable — Done: unnecessary inline marks removed (c46ebec322); visitBottomUp changed to pre-order (ef2806e4ab, e40dffe55a); intrinsic inlining shortcut after the getcaller check (376ce8c880). Left open: nothing noted.
• Open-coded defers and defer lowering — Done: stack-allocated defer records (fff4f599fe). Left open: defers still cost a runtime call per execution.
• Statement boundaries (is_stmt) and source positions through the optimizer — Done: move marks from jumps to targets (82af9e6749), OFOR body pos (7afd58d458), line tables indexed by source file (6081a9f7e6). Left open: better heuristic skipping not-statement values.
• Range loops, append and map idioms in walk — Done: map initializers evaluated incrementally (ee59c06acb), callnew ported to SSA (23b476a3c8) and no newobject for zero-sized types (c1050a8e54). Left open: nothing noted.
• Rewrite-rule generator, typed Aux/AuxInt, and rule syntax — Done: multi-| expansion (48d3c32ba9), countRule (0047353c53), deadcode pass storage in ssa.Cache (c9ccdf1f8c). Left open: nothing noted.
• Write-barrier elision and the writebarrier pass — Done: tracking zeroed object parts (ca36af215f), volatile values copied before barrier call (f23c601bf9), crash on barrier insertion fixed (316ac4f330). Left open: nothing noted.
• Memory-op optimizations: memmove, Move/Zero, dead stores, nil checks — Done: nil-check not moved across VarDef (64c134f90f), slice pointers non-nil (933e34ac99). Left open: nothing noted.
• Arithmetic strength reduction, divisibility and intrinsics — Done: signed divisibility (68819fb6d2, 4d9dd35806, 44343c777c), 61945fc502 (no panicshift for masked shifts), 68d4b1265e. Left open: nothing noted.
• CFG and control-flow passes: branchelim, fuse, shortcircuit, phiopt — Done: shortcircuit (52ae04fdfc^1.14, 1.14), fuseIf (ddb5d0db37, e7b7f87432), phi tighten (c1544ff906). Left open: nothing noted.
• Compiler front of walk/order: ordering fixes and the dev.regabi IR refactor (package walk) — Done: short-circuit ordering (4a9064ef41), callnew to SSA (23b476a3c8), maplit incrementally (ee59c06acb), sinit methods (ee2836048c). Left open: nothing noted.

Other changes

• Walk/SSA fixes and cleanups internal — statictmp name collisions (08831b150c), types.SoleComponent (9892ccff23), dead code (01971b97c1), -d=ssa/ crash (be9c534cde), type switch with broken case (8ee9bca272), “badger” optimization removed (c63dc6d459), float comparison flags (a85afef277), SCC code moved to its own file (829c140f14), struct-in-interface bug (d47db6dc0c), append ICE (c4f87ed26f), escape messages trimmed (131eb8fbf8), new panicindex names (48ef01051a), ORESULT added and OINDREGSP removed (336f951b07), go/defer variadic ICE (9f9e17a82f), index-panic line numbers (e7d08b6fe6), maplit dynamic entry (aaf40f8f98), unsafeValue shifts (06ef108cec), intrinsics-disabled build (c10db03cbe), rule-note docs (49ad7bc67c, f61cf6f313), regalloc []valState reuse and postorder (4ae31dc8c5, 5c3f3fbd0f), fix bad rebase (e5fb1c6d7a), inline-mark docs (19f5c233d1, 6c842cc610), cancellation spelling (5781df421e).

Backends and assemblers

From Backends and assemblers (Go 1.12–1.17)

Intrinsics and ports: Add64/Sub64 carry chains, wasm intrinsics and options, ABI wrappers for linkname'd symbols, index-carrying bounds failures, s390x sequentially consistent atomics.

• Register-based ABI (ABIInternal) and ABI wrappers — Done: ABI wrappers for linkname’d symbols (b402bd4499); -allabis mode removed (74d92db8d7). Left open: wrappers are aliases for the stack ABI only; no register convention exists.
• Rewrite-rule generator (rulegen): ellipses, commutativity loops, typed aux — Done: magic-variable prediction tightened (53948127d3), for-loop verbosity (0fbf681840), stopping the shadowing of the bool type in rules (9f56845f2c), 07b4b4a1a8 adds a scale field to SSA ops. Left open: generated files still huge.
• amd64 lowering: read-modify-write, load-op, addressing modes pass, intrinsic-friendly rules — Done: a SETcc-store rule typed incorrectly is corrected (23f3ea82b9); no other amd64-specific design work. Left open: nothing noted.
• arm64 backend and assembler — Done: v8.1 atomics (448089854a), bits intrinsics (5714c91b53, f8f265b9cf, dd91269b7c, 159b2de442, 4e2b0dda8c, 192b675f17), FCMP $0 (27cce773d3), changed FP flags (6efd51c6b7), TSTW fix (2ef8abb41f), 4ea7aa7cf3 uses R20/R21 in Duff’s devices. Left open: nothing noted.
• PPC64 / POWER backend and assembler — Done: POWER9 CNTTZ (3023d7da49), RotateLeft (f2a18b1456), Add64 (50ad09418e), XX1-form encoding fix (259de39375), mid-stack-inlining NOP (2d3474043c, b098c0f467). Left open: nothing noted.
• s390x backend: compare-and-branch, intrinsics, assembler — Done: atomic ordering (ac8dbe7747), Add64/Sub64 (2c1b5130aa), RISBG family (0f79510dc5), IPM (6966b67510), RestArgs (9c843f031d), optab param (e61985427e). Left open: spills of the carry per loop iteration noted in 2c1b5130aa (“may be able to reduce”).
• 386, ARM (32-bit), MIPS/MIPS64 and the 387 removal — Done: ARM ReverseBytes16 (fee84cc905), MIPS64 UNPREDICTABLE fix (95d4e6158b), a189467cda. Left open: nothing noted.
• WebAssembly backend — Done: intrinsics, GOWASM options, global/PC cleanup, SP caching (5ee1b84959, 4d23cbc671, cf8cc7f63c, 496b8dbbfc, 203e188837, 72d24a7484, 2396101e05). Left open: nothing noted.
• math/bits, atomic and runtime intrinsics (cross-architecture) — Done: arm64/ppc64x/s390x Add/Sub intrinsics, wasm, 4a4e05b0b1, divisibility (a28a942768). Left open: nothing noted.
• SSA infrastructure passes: layout, regalloc, scheduling, flagalloc, block shape — Done: 80b6812d7b, 4ae31dc8c5, 8a317ebc0f, 2c423f063b. Left open: nothing noted.
• Debug info generated by the backend: statements, location lists, line tables — Done: 82af9e6749, 6081a9f7e6, 68a98d5279. Left open: nothing noted.
• New object file format and content-addressable symbols (dev.link, assembler side) — Done: cc5eaf9346, 134ef176f0, 807761f334. Left open: nothing noted.
• Assembler directives and tooling: PCALIGN/ALIGN, FuncInfo flags, prologue handling — Done: DATA validation (f31305b71b), BSWAPW reject (720af3c8c4), cb8aefd3b0 ADJSP. Left open: nothing noted.

Other changes

• Assembler and rulegen odds and ends internal — MIPS OP_IRR register fix (ec01d8f74b), rulegen accesses last argument first (04f1b65cc6), -gensymabis accepts TEXT f+0(SB) (f766b68023).
• Bounds-check failure messages carry index and length user-visible — runtime errors like index out of range [3] with length 3 and slice bounds out of range [:4] with capacity 3 (2c423f063b, 48ef01051a).
• Misc internal — e881604d1c, 337a1bde02, 12e63226b9, 07b4b4a1a8, d98e0720bc, e4665da9bc, ad6c691542 (remove AUNDEF), 40df9cc606 (KeepAlive on stack object), 43001a0dc9, 68c664141c, c70a7849af, a189467cda, 250b96a7bf, fc1e6915dc, b098c0f467, f125b32d19, 4ebc6514fa (EVEX RIP-relative encoding fix), 769fda2d51, 0a338f75d4, f495f549ac, e61985427e, 2ef8abb41f.

Linker and object files

From Linker and object files (Go 1.10–1.17)

mmapped output and object data, Reloc shrunk, pctab deduplication in pclntab, -strictdups, runtime version info symbol, AIX external linking and PIE, riscv64 groundwork, GOWASM.

• Linker performance and memory engineering — Done: mmap of output (b2f94d3e88) and object data (dbe32284ff), Reloc shrink (8ef45cf60b), fix of a seek-syscall regression introduced by the mmap’d reader (0793c81009), pctab dedup in pclntab (below), -strictdups checking (d923309a17, refined cacab64555), 9ac471a87d read-only strings. Left open: relocations still applied in a separate pass over heap data.
• pclntab, funcdata and pc tables — Done: off-by-one fixed in ftabaddstring (7f9e0220cd, few KB saved), d79aea6b96 pctab dedup, 134ef176f0 uses encoding/binary for varints, 3a62f4ee40/6d64dd731b cleanups, d6b06f0254 (see build-info thread). Left open: names, files, tables still in one symbol.
• Dead-code elimination and method pruning — Done: 2cdebb5174 removes a stale reference; 951143cf14 raises the call limit in the stack-bound check. Left open: nothing noted.
• DWARF generation in the linker — Done: ed2fce2d87 dwarf64 in .debug_frame, e29f74efb9 exports package name in debug_info, 4d8a37a6d9 fixes pubnames/pubtypes, b56d1bad29 call_line as data4 on iOS, 26954bde44/3f1422c799 __DWARF segment protection on macOS, d41a0a0690 removes a large slice in scopePCs. Left open: nothing noted.
• DWARF compression and Mach-O dsymutil combining — Done: 248444d5eb, 0fe1986a72, 807761f334 revises a change because LLDB is picky. Left open: nothing noted.
• Mach-O and Darwin support — Done: bitcode builds for iOS/tvOS/watchOS (ba965640a4, 1bd974eeb7^1.14, f4e32aeed1^1.14), 277609f844 copies platform version commands to go.o, a74e01204e consolidates platform setup, 4cd6c3bac7 bumps macOS/SDK version to 10.9, 637f34fee0/c90f6dd496 allow duplicate weak symbols on Mach-O, 3cb92fcba7 c-archive compatibility. Left open: nothing noted.
• PE / Windows — Done: e883d000f4 stops generating NT 4 compat headers (subsystem version 6.1), 1a423bec00^1.14 (header copy-paste fix). Left open: nothing noted.
• AIX / XCOFF — Done: external linking and c-archive (80f10965ee, f0749c74fd, 359fb4a9af export file, 3cf89e509b, 697f4183e6, cf952e9e62 PIE, cb8054a6b6/0cd74d1f11 trampolines/C trampolines, 2deda8792a, d3631955d4, 0ff9df6b53, a891f2e2ae), 0c9e0c257b .go.buildinfo. Left open: DWARF disabled with old ld.
• WebAssembly — Done: 99e223289b optimises the data section, fb9b818bbd caps data segments at 100000, b434bbf197 adds the GOWASM environment variable (comma-separated experimental wasm features, none defined yet) user-visible, 460f9c6068 optimises memory allocation. Left open: no experimental features exist yet.
• Build modes: PIE, plugin, c-shared, c-archive, shared libraries — Done: PIE with internal link on linux/arm64 including GOT/PLT and many R_AARCH64_* relocations (d2765de863), PIE and c-archive on aix (cf952e9e62, 697f4183e6), c-archive Mach-O compatibility (3cb92fcba7), e4665da9bc reproducible toolchain builds under PIE. Left open: nothing noted.
• Host object loading and external linking — Done: 9f9c5fa8c7 -a with external linker, 3235f7c072 duplicate ELF section names tolerated, 83f205fa88 R_AARCH64_LDST128_ABS_LO12_NC, e27402aee0 configurable default dynamic linker/loader user-visible, a4f9c2a29e openbsd/arm64, 4590abe072. Left open: nothing noted.
• Architecture ports and trampoline insertion — Done: a4f9c2a29e openbsd/arm64, a3863fc18a fix constant. Left open: nothing noted.
• GOEXPERIMENT plumbing and tool configuration — Done: 4814e7d591 includes full GOEXPERIMENT flags in the tool ID for the cache key (release versions previously ignored them), a5248acd91^1.12 enables GODEBUGCPU in non-experimental builds. Left open: nothing noted.
• Build identity, buildinfo and reproducibility — Done: d6b06f0254, 4891a3b66c, 0c9e0c257b .go.buildinfo in XCOFF symtab. Left open: nothing noted.

Other changes

• Small items internal — 4ba69a9a17 (ppc64 processor-level selection), 2034fbab5b (inline marks reuse existing instructions), d949d0b925 (init function reorganisation), 804a4024ec/bc588d4d92 (file handle leaks), 850844ef65, 93fcebaf31 (no writes to read-only memory in addstrdata), 096ab3c21b/4fdeb73fed (iOS simulator syscall suffixes), 76659e4797.
• Wasm/XCOFF/AIX — see threads.
• -strictdups user-visible — d923309a17, cacab64555, 4590abe072, 07ca28d529^1.17 (1.17 BSS fix).
• Increase ELF reloc reserve internal — 3b37ff453e; 9eb403159d deferreturn detector; 7498e8f5a2 memprofile legacy format for compilebench; d41a0a0690 scopePCs.
• GOWASM / env -w user-visible — b434bbf197, f0e9754696.
• Stack check limit internal — 951143cf14.
• Dynsym info internal — 12dbd20a50^1.14, fa7d40abe0^1.14 (1.14).