V 0.4.12

19 Sep 2025

Improvements in the language

• json2: replace encoder with a new implementation. It's 70% faster than the old json2, and 110% faster than json that is based on cJSON (#25224)
• Virtual C consts with custom types (const C.MY_CONST u8)
• Support -div-by-zero-is-zero, which allows for x / 0 == 0 and x % 0 == x, avoiding division by zero traps/panics (#24981)
• Limit -div-by-zero-is-zero influence to just the integer types (for f32 and f64, / produces a +inf or -inf value, and the program continues to run)
• VLS mode for the language server in pure V
• Add support for @OS, @CCOMPILER @BACKEND and @PLATFORM (#25174)

Breaking changes

• Deprecate gx and replace all occurences with gg (which now contains all the functionality of gx) (#24966)

Checker improvements/fixes

• Fix sizeof(T) usage in generic struct (fix #24806) (#24808)
• Add $if sizeof(T) == int_literal { support (#24831)
• Improve virtual C consts
• Markused,checker: fix hello world size after the introduction of builtin.closure in 2d87ac4 (#24989)
• Remove dump() dependency from ComptimeFor (#25000)
• Cleanup - remove unused c.using_new_err_struct (#25036)
• Cleanup err removal (#25043)
• Add comptime support for s390x, ppc64le and loongarch64 platforms (#25048)
• Allow for v -is_o -o x mm.v, where mm.v starts with module abc (i.e. not just module main)
• Fix calls with result propagation, using other consts, in const declaration expressions (fix #21609) (#25060)
• Fix array init with interface (fix #24255) (#25073)
• Fix missing map float key duplicated checking (fix #25098) (#25117)
• Fix missing check for struct generic init from call (fix #25084) (#25119)
• Fix missing check for empty array to generic param (fix #25056) (#25118)
• Rewrite comptime_if_cond() to support comptime if cond evaluate (fix #24938) (fix #25099) (#25122)
• Add error for struct not init (fix #24893) (#25134)
• Fix sql insert expr propagate result (fix #24833) (#25136)
• Fix checking return type call disregarding unwrapping (fix #25140) (#25143)
• Ensure the defer behavior matches that of cgen (fix #25148) (#25146)
• Nil check for c.table.cur_fn in gen_branch_context_string() (fix #25170) (#25171)
• Relax the "unreachable code after a @[noreturn] call" error to a warning to reduce prototyping friction (#25173)
• Fix multi return arg passing checking (fix #25167) (fix #25180) (#25177)
• Use keywords matcher trie for imported symbol presence checks, instead of x in p.imported_symbol (#25201)
• Fix iteration over mutable option (fix #24860) (#25199)
• Add T.typ and T.unaliased_typ checking to $match (fix #25200) (#25202)
• Add more checks for map.delete (fix #25204) (#25205)
• Fix static init var (fix #25203) (#25209)
• Add top level comptime support for $match @OS { too (#25222)
• Comptime match only eval true branch (fix #25223) (#25225)
• Fix multi return var passing to fn arg (potential fix for #24870) (#25250)
• Prevent usage of imported module name prefix as identifier names, to avoid cgen collisions (#25280)
• Disallow duplicate export names (fix #25301) (#25302)
• Reduce the verboseness of unsupported size ... for global messages, for v -b native examples/hello_world.v

Parser improvements

• Split parser methods to files based on topic (#24786)
• Fix arch loongarch64 comptime support (fix #24906) (#24907)
• Fix const error
• pref,parser: implement support for -force-bounds-checking to enable easier testing of functions tagged with @[direct_array_access] (essentially turning off that flag)
• Allow keyword as struct param key on fn call (fix #24957) (#24958)
• Fix syntax error for for c in [othermod.Struct{field: 255}] { (fix #24943) (#24978)
• Reduce calls to util.contains_capital
• Fix overriding of fn names in -translated mode (fix #25024) (#25061)
• Fix asm modifier parsing (allow for =r, =&r, +r, +&r,=m,=rm,=@ccl, =*r) (fix #25070) (#25072)
• Allow using aliased types in interface method implementations (provide backwards compatibility to ui, during the migration of code from gx to gg) (#25106)
• Fix interface method declaration with fixed array return type (fix #25137) (#25145)
• Prepare for eliminating a warning for v -cross -o vc/v.c cmd/v (part 1) (reduce CI annotation noise)
• Add duplicate import symbol detect (fix #25185) (#25187)
• vfmt,parser: move mark used from vfmt to parser (#25190)
• v.ast: add a mod field to ast.FnTypeDecl too

Compiler internals

• scanner: fix multi-level string interpolation in if/match branch (#24805)
• markused: fix mark for array init from sumtype (fix #24887) (#24889)
• markused: whitelist _option_none too (fix #24862) (#24885)
• markused: remove @[markused] from option and result fns (#24900)
• markused: skip unused symbols, dump fns and generic specialization (fix #24921) (fix #24927) (#24924)
• parser,markused: support @[markused] for interface declarations too (#24963)
• markused: fix interface fields and chan usage (fix #24961) (#24962)
• v.builder: add a clearer error message for v -shared run empty.v (issue found by Felipe Pena)
• markused: use eprintln for PANIC DEPS too (for consistency and easier redirection for the whole trace)
• v.util: add support for setting VUTIL_RETRY_MAX_COUNT=1 to ease the workflow for developing backends
• markused: improve the tracking of used closures (#25009)
• markused: improve array resources tracking + remove all_fns loop for orm (#25007)
• markused: fix generic map index (fix #25012) (#25022)
• markused: improve array tracking (range, gated) (#25023)
• markused: fix option tracking on sumtype (fix #25025) (#25028)
• markused: fix thread type mark by go/spawn expr (fix #25049) (#25054)
• scanner: refactor string interpolation (fix #24198) (#25053)
• markused: fix array append c code dependency (fix #25057) (#25058)
• markused: fix option array element (fix #23089) (#25179)
• markused: fix option map value (fix #25186) (#25188)
• parser,fmt,markused: add top level comptime $if support (enable $if platform { import module struct Abc {} }) (#25216)
• v.builder: add -DNO_DEBUGGING in addition to -DNDEBUG, when compiling with -prod
• v.builder: support -d trace_type_symbols_after_checker
• scanner: uncomment working rune test (#25305)
• v.util: fix handling of "start \u005c${...} end" in cgen (fix #25304) (#25306)
• markused: fix marking of mutable generic method calls (fix #25312) (#25314)

Standard library

• x.crypto: initial addition of curve25519 module (#24748)
• thirdparty: add NDEBUG check before glGetErrorCode if-statement in sokol_gfx.h (#24754)
• math.big: remove unnecessary code from / and % (the same is done in div_mod, which they call) (#24766)
• builtin: add a rune iterator method to strings, allowing for for i, r in s.runes_iterator() { without first allocating an array for all the runes (#24769)
• builtin: support -d builtin_free_nop to help diagnose problems with too early manual free() calls
• builtin: use s.runes_iterator() in trim_runes/2 to avoid needless allocation
• builtin: add string.expand_tabs() (#24781)
• os: do not resolve symlinks in os.find_abs_path_of_executable/1 (fix #24759) (#24761)
• os: improve documentation (#24790)
• gg: allow for -d gg_memory_trace_frame to be used in combination with -prealloc -d prealloc_dump
• sync: add SpinLock (#24788)
• os: fix documentation for environ function (#24796)
• sync: fix documentation for new_spin_lock function (#24795)
• sync: add implementation for WaitGroup.go/1, add test (#24797)
• sync: improve documentation (#24799)
• sync: fix spin lock, add destroy() and try_lock(), add valgrind annotate support (#24798)
• os: add os.write_bytes/2 as a complement to os.read_bytes/1, add test
• sync: use SpinLock for channel (fix #24680) (#24802)
• crypto: fix ambiguous expressions in DES implementation (#24814)
• sync: use an atomic counter in test_waitgroup_go in waitgroup_test.v
• datatypes: add lockfree version of counter and ringbuffer (#24839)
• sync: add thread local storage (TLS) support (#24849)
• math.unsigned: fix rotate_left() for uint256, add test (#24872)
• math.unsigned: replace untested comments for uint256 public APIs (#24873)
• log: use @[noinline] for level_from_tag/1 and target_from_label/1 to avoid triggering panics for programs using log, compiled with -prod and -cc gcc>10 (fix 8000 #24874)
• math.big: fix toom-cook 3-way multiplication (#24888)
• runtime: add used_memory() (#24897)
• runtime: add note for the availability of the used_memory implementation (#24913)
• os: remove commented code in home_dir() function (#24929)
• math.big: fix the order of calculations in mod_pow() to improve performance (#24935)
• math.big: add shrink zeros to karatsuba and toom-cook (#24937)
• math.big: fix big_mod_pow() (#24939)
• os,runtime: move some C struct and fn def to builtin (#24942)
• math.big: fix validate_string and integer_from_regular_string (check for characters.len > 0, before accessing characters[0])
• builtin: prepare for adding a -force-bounds-checking option
• strconv: fix bounds check bug, discovered by the equivalent of ./v -g -force-bounds-checking test vlib/toml/ (thanks to tankf33der)
• builtin: fix OOB bugs in s.is_bin, s.is_oct, s.is_hex, discovered through ./v -force-bounds-checking test vlib/builtin/
• regex: fix OOB bug discovered through ./v -g -force-bounds-checking vlib/regex/ (fix by @penguindark) (#24960)
• time: fix custom_format panic (fix #24977) (#24987)
• time: fix more panics in the supported specifiers in Time.custom_format/1 (#24988)
• vlib: add archive.tar module to enable reading of .tar ang .tar.gz files (#24995)
• builtin: fix warnings for ./v doc -m -f html vlib/builtin/
• sokol.gfx: set the missed array_count field too in the set_vert_uniform and set_frag_uniform APIs (#25019)
  ...