Every invariant `tests/ic` checked was IC-against-IC — clean == incremental, a
no-op edit changes nothing, a body edit moves no interface cookie. An IC that is
*consistently* wrong satisfies all of them, and that is exactly how two silent
miscompilations survived. `koch bootic` has the same blind spot: it proves the
compiler reproduces itself, not that it agrees with the reference backend.
Two mechanisms, at different scales.
**The oracle, in the metamorphic runner.** Every successful step is now also
compiled with `nim c` and run, and the two outputs must agree. Unlike the
hand-written `expect:` strings this needs no foresight from the test author: it
compares everything the program does, not only what someone thought to print,
which is what a silently-skipped destructor evades. `no-oracle` opts out.
The format also grew the expressiveness the recent bug hunt showed was missing —
every one of these described a state the suite could not reach:
* `#!DELETE <file>` removes a module. Deleting a still-imported file moves no
mtime, so nothing re-fires.
* `#!FLAGS <switches>` changes the compiler switches between steps. A config
change is not a file either.
* `fails: <substring>` asserts that BOTH compilers reject the program with that
text. Previously every step had to succeed, so the whole error path — and
recovery from it — was untested.
Six regression tests cover the eight bugs the last round fixed.
`testament r <file>` now dispatches metamorphic tests like `testament cat ic`.
**`testament --ic` runs the whole corpus through the incremental compiler**, so
IC inherits ~10k programs with expected output instead of 30 bespoke tests.
Two things had to change for that to mean anything:
* `nimcacheDir` now keys on the `matrix:` entry too. Two matrix variants of one
file are two different compilations; sharing a cache meant each run
invalidated what the previous left — harmless for a backend that caches only
object files, useless for an incremental one.
* About half the corpus overrides the command wholesale (`cmd: "nim c --gc:arc
$file"`), bypassing both `$target` and `$options`. Those are rewritten to `ic`
and given a private cache.
**Warm cache, hastur-style.** A generated warmup program pulling in `system` and
the most-imported stdlib modules is compiled once per distinct compile
configuration into `nimcache/ic_warmup_<hash>`, and each test's empty cache is
seeded from it with mtimes preserved (nifmake compares output-mtime >
input-mtime, so stamping the copies "now" re-fires the whole graph). Only
program-independent artifacts are copied: the frontend NIFs and cookies plus the
per-module `lower`/`cg` output. The `.c`/`.o` are left behind on purpose — the
merge decision is whole-program, so they are re-rendered for every program
anyway.
`tests/destructor` (97 runs): `nim c` 35s cold / 32s warm; `nim ic` ~3m30 cold /
**9.8s warm**.
Compiler changes this required or uncovered:
* `merge` read the live-module list from a manifest the driver writes instead of
globbing `*.c.nif` off the nimcache. Globbing absorbed artifacts belonging to
any other program sharing the directory — which is what made a prefilled cache
produce undefined symbols at link.
* The build-arg signature no longer includes `--icproject:`/`--icPreparsedConfig:`
(they name where a build lives, not what it produces, so two caches holding
identical artifacts got different signatures). The precompiled config still
counts, by content hash, minus its `(nimcache …)` line.
* `.s.deps` seeding is speculative and runs before the prune, so a sidecar entry
that has gone stale (an import that a `when` no longer takes) can be dropped
instead of lingering forever; a pruned module's scan artifacts are deleted so
an edit-accumulated cache still matches a clean one.
* A failed nifmake run no longer prints an `Error:` of its own. The children have
already reported; adding a build-system status as the LAST error hid the
compiler's real message from anything reading the final error — every
reject-style test under `nim ic` said "nifmake failed with exit code: 1".
* `--mm:hooks` fed the mm mode to an on/off switch and failed outright with
"'on' or 'off' expected, but 'hooks' found". Pre-existing and unrelated to IC;
only reachable through the explicit switch, since `--newruntime` sets
`selectedGC` directly.
Running `tests/destructor` under `--ic` currently leaves 10 failures. They are
genuine IC defects, not harness noise (all 97 pass under `nim c`) — the clearest
is `tglobaldestructor`: `graph.globalDestructors` is accumulated while injecting
destructors into a module's top level, but the main module's `cg` — which emits
the teardown — is a different process, so a module-level `var` with a `=destroy`
is never destroyed. Same shape as the init/datInit metas, and it wants the same
fix: record it in the `.c.nif` head.
Validation: `koch bootic` reaches its byte-identical fixed point; `tests/ic` is
36/36; arc, destructor, macros, template, iter, closure, ccg, codegen, types and
effects pass under `nim c`, with generics showing only its pre-existing failure.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Grinding a small figdraw-based program under `nim ic` and diffing its output
against the classic backend surfaced eight bugs, four of which silently produced
a wrong binary rather than an error.
Frontend / build graph (`deps.nim`):
* Dead `when`-guarded imports were compiled anyway. `when someStrdefine == "x":
import y` is `cvUnknown` to the scanner, which conservatively keeps the edge —
right for an edge, but it also gave `y` its own `nim m` rule, so a build died
on a package the user never installed because they never selected that backend.
Track which edges are speculative and drop a speculative subtree that cannot
compile; if the guard was in fact live, the discovery fixpoint puts the node
back with the honest `cannot open file`.
* Deleting a still-imported module went unnoticed: no mtime moves, so nothing
re-fires and `nim ic` relinked a stale binary while `nim c` reported `cannot
open file`. Report an unresolvable import from a non-speculatively reached
module during the graph scan.
* Macro-generated imports were discovered once and then forgotten. Discovery
only ran after a failure and the graph is re-derived statically every run, so
on a warm build the discovered module had no rules at all and editing it
changed nothing. Seed the graph from the `.s.deps` sidecars up front.
* Config changes invalidated nothing. nifmake decides staleness from file mtimes
and never looks at a rule's command line, so `-d:foo=bar` / `--mm:` / `--threads:`
regenerated the build file with the new switches and re-fired zero rules.
Reify the configuration as a file and make it an input of every rule.
* Command-line switches never reached the children: they replay the project's
config files, never the driver's argv, so `nim ic --opt:speed` produced a
byte-identical debug binary (likewise `--panics`, `--experimental`, `--passC`).
Forward the driver's switches, minus the ones that must differ per child.
Artifacts and codegen:
* A failed `nim m` still wrote its `.s.bif` and cookies, so nifmake saw the rule
as satisfied on the next run: `nim ic` then reported success for a program that
does not compile, and generated code from error-bearing AST (or hit an internal
error in `ccgexprs`). Never persist an artifact when `errorCounter > 0`.
* Top-level destructors were never injected. `sfInjectDestructors` lives on the
module symbol, which `moduleFromNifFile` rebuilds from scratch, so
`genTopLevelStmt` skipped `injectDestructorCalls` entirely: a module-level
`block: let h = openHandle()` never ran `=destroy`. Persist the flag as a
`(modflags)` record. `injectdestructors` also has to tolerate the
`nkReplayAction` entries the loader prepends to `topLevel`.
* `nfFirstWrite` / `nfLastRead` were dropped by the serializer. A sym node is
written as a bare NIF `SymUse` token, which has nowhere to put node flags, so
the frontend's move analysis never reached the backend: EVERY first assignment
to a destructor-bearing local compiled as `=sink`, i.e. `=destroy` on
still-zeroed memory followed by a copy, and no read was ever a move. Wrap a sym
use in `(nflags ...)` when it carries persistent node flags.
`icFormatVersion` 34 -> 35 for the two new NIF records.
Validation: `koch bootic` reaches its byte-identical fixed point; two clean-cache
builds from the same compiler are identical; testament `arc`, `destructor`,
`macros`, `template`, `iter`, `closure`, `ccg`, `codegen`, `types` and `effects`
pass, and `generics`, `ic` and `stdlib` show exactly the pre-existing failures.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
fixes#26015
Fixes imported global variables with codegenDecl being emitted as
definitions instead of extern declarations.
A variable’s codegenDecl format should customize its definition in the
owning module. Other modules referencing the variable must emit a normal
declaration:
```c
extern NI variable;
```
After the variable-declaration builder refactor, genVarPrototype passed
Extern visibility to addVar. However, the sfCodegenDecl branch returned
before applying that visibility. This caused importing modules to emit
another tentative definition, resulting in duplicate-symbol linker
errors.
The fix restores the previous distinction between the custom definition
and cross-module prototypes. It also adds C and C++ regression coverage
for both direct access and access through an inline procedure.
follows up https://github.com/nim-lang/Nim/pull/24423
fixes#26123
`cast[T](x)` is a transparent path expression for compiler analysis.
Previously, move/alias analysis could fail to see a later use through a
cast and incorrectly mark the source as moved, causing the issue’s
segmentation fault.
for views,
https://nim-lang.org/docs/manual_experimental.html#view-types-path-expressions:
A cast expression cast[T](e) is a path expression.
It also affects skipConvDfa, isAnalysableFieldAccess, and aliases. And I
might narrow it down for the two cases above mentioned if it causes
problems
fixes#25992
```nim
type
Foo = object
case kind: bool
of true:
a: ref Bar # 8 bytes (pointer)
of false:
b: int # 4 bytes
```
specializeResetT for b emits accessor.b = 0 — writes 4 bytes
But the union is 8 bytes wide (sized by the largest branch)
The remaining 4 bytes where a used to live are untouched
Those stale bytes could contain a heap pointer the GC traces → crash
Add nimZeroMem after specializeResetN for case objects to clear the
entire union including unused branch bytes.
We defer copying the AST during generic instantiation until a cache miss
and fetch from cache based on bindings. On miss, we fall back to the old
logic and populate the cache.
This gains us a roughly 36% reduction in memory usage during bootstrap,
from `799.242MiB` down to `508.672MiB` on my machine.
For another point of reference, nimbus-eth2 goes from `10.5GB` memory
usage to `7.5GB`.
Independent companion to #26090 which together with this one yields a
bit under 20% faster compiles (or at least `--compileOnly` bootstraps)
on ORC.
…haracterization with--warning:ResultUsed:on
fixes#26062
> A return statement with no expression is shorthand for return result.
> ResultUsed: Warn about the usage of the built-in result variable.
> A procedure that does not have any return statement and does not use
the special result variable returns the value of its last expression.
`unapplyBlockContext` reset `inEnforcedGcSafe` and
`inEnforcedNoSideEffects` to false whenever a `{.cast(gcsafe).}` or
`{.cast(noSideEffect).}` block ended. When such a block is nested inside
another block of the same cast, the inner block's exit switched
enforcement back on for the rest of the enclosing block, so statements
lexically inside the outer cast were rejected.
The fix saves both flags in `PragmaBlockContext` when the block context
is created and restores the saved values on exit. That matches how every
other piece of block state there (`locked`, `exc`, `tags`, `forbids`) is
already handled; these two bools were the only ones reset to a constant
instead of restored.
No change for non-nested blocks: entering from the non-enforced state
saves false, so exit still clears the flag. A statement after the outer
block is still rejected as before.
Test covers nested `cast(gcsafe)` and nested `cast(noSideEffect)`.
`tests/effects` passes unchanged (49/49, same as stock).
Boostrap without linking is (conservatively) 17% faster on my machine.
Test setup runs the compiler compiling itself under ORC in release mode
from a clean cache and no C compilation (`--compileOnly`.)
Multiple samples are gathered before judging a potential optimization.
The test suite passes locally before push and bootstrap is tested with
strict views (mostly as a sanity check).
Tests are fair in the sense that they compile the same git worktree and
produce identical C output.
Refc will see less or no benefit.
Changes:
- Save tree traversals in `considerGenSyms` when no mappings exist
- Inline `maybeSkipDistinct` into `typeRel` for a safe cursor
- Only skip to static when there is a static type to reach in
`paramTypesMatchAux`
- Disable overflow checks for hashes
- Disable bounds checks for `nextIdentIter`
- Use cursor annotation when judged safe
- Use lent annotation for ast accessors
Spiritual companion to #26084
## Summary
- nimpretty with non-default \--indent\ (e.g. 3 or 10) produced invalid
indentation in if/block/try expression regions because layouter kept the
original column when \keepIndents > 0\ and ignored \indWidth\.
- Rebase the column onto \indWidth\ using the relative offset from the
enclosing block baseline (\indentStack[^1]\).
## Root cause
\parser.nim\'s \
imprettyDontTouch\ template sets \keepIndents\ for if/block/try
expressions. layouter in the \keepIndents > 0\ branch used \ ok.indent\
(source column) directly as \indentLevel\ without scaling by \indWidth\,
so lines in these regions kept the original column and misaligned with
the rest of the file when \--indent\ differed from source indent width.
## Fix
\\\
im
em.indentLevel = em.indentStack.high * em.indWidth +
(tok.indent - em.indentStack[^1])
\\\
Keeps the relative offset from the enclosing block baseline but rebases
onto \indWidth\. At default \--indent:2\ the offset equals \indWidth\,
so output is unchanged (backwards compatible).
## Testing
- 12 custom cases x 3 indent values (2/3/10) = 36/36 pass
- nimpretty self-test suite 7/7 pass (no regression at default indent)
- 5 keepIndents scenarios (if/block/try expression continuation
alignment) that failed at indent:3/10 now pass
Fixes#20078.
fixes#25942fixes#25938
After a successful match to a concrete static T, normalizes an empty
static container literal to the formal payload type before binding it.
This prevents `static[set[empty]]({})` from leaking into the
instantiated proc body.
fixes#26045;
fixes#26046
The fix isolates compiler option state while semantically checking each
when nimvm branch.
compiler/semexprs.nim:2745 snapshots the option stack, compiler options,
diagnostics settings, and enabled features. It analyzes one branch and
restores that state in finally. Both the nimvm and else branches use
this function.
This prevents:
```nim
when nimvm:
{.push overflowChecks: off.}
```
from disabling overflow checks in following runtime code. It also means
a {.pop.} in the opposite branch correctly reports that it has no
corresponding {.push.}.
`distinctBase` results in typedesc, so `set[T.distinctBase]` received
`typedesc[range[...]]` as its element type, which `isOrdinalType`
rejects. Strip the wrapper in `semSet` before storing the element type
and checking ordinality.
Also add `tyFromExpr` to the deferred-check set so the error doesn't
fire prematurely inside generic bodies - same pattern already used by
`semArray`.
fixes#26010
Cursors do not own their values and therefore cannot transfer ownership
through move.
Reject move(cursor) during semantic analysis and share the
cursor-location check
between semantic analysis and destructor injection.
Fixes#23615
## Root cause
The leak does not require async at all -- this minimal closure iterator
leaks the exception and its stacktrace seq under ARC/ORC:
```nim
iterator it(): int {.closure.} =
try:
yield 1 # try spanning a yield => closureiters transform
raise newException(ValueError, "x")
except ValueError: # typed except => generated `of` check
discard
yield 2
```
A bare `except:` does not leak; a *typed* `except` does:
1. `collectExceptState` in `compiler/closureiters.nim` generates the
except-branch type check as `of(getCurrentException(), T)`, using the
raw generic magic sym from `getSysMagic("of", mOf)`.
2. `injectdestructors` skips call arguments whose *formal* parameter
type is `isCompileTimeOnly`, and the raw generic `of` sym's formal
params are `tyGenericParam` so both arguments of the generated `of` call
are never processed.
3. `getCurrentException()` increfs `currException` via `=copy` into its
result. Since the arc pass never wraps that owned temp in a destroy
(`--expandArc` shows the condition left untouched, while a user-written
`if f() of ValueError` in the same iterator gets a `:tmpD` +
`=destroy`), the caught exception's refcount stays +1 forever.
Every `try: await x() except SomeError` in async code has this shape, so
each caught async exception leaked once.
## Fix
The state-machine wrapper already stores the active exception in the
`:curExc` env field before jumping to the except landing state, and
`currException == :curExc` on every path into that state. The generated
condition now references the env field via `ctx.newCurExcAccess()`
instead of calling `getCurrentException()` again -- no ownership
transfer, no temp to destroy, one fewer runtime call.
Note: the underlying `injectdestructors` behavior (skipping args of
calls whose formal params are raw `tyGenericParam`, e.g. from
`getSysMagic`) is a separate latent gap that could affect other
compiler-generated code; it is intentionally left untouched here.
## Valgrind, before and after
Exact code and command from the issue, on Linux (Valgrind 3.19):
```
nim c -d:danger --mm:orc --debugger:native --threads:off -d:useMalloc bug.nim
valgrind --leak-check=full --show-leak-kinds=all ./bug
```
Before (devel):
```
==14663== HEAP SUMMARY:
==14663== in use at exit: 136 bytes in 2 blocks
==14663== total heap usage: 22 allocs, 20 frees, 116,466 bytes allocated
==14663==
==14663== 56 bytes in 1 blocks are indirectly lost in loss record 1 of 2
==14663== at 0x488A1C4: realloc (vg_replace_malloc.c:1437)
==14663== by 0x10C663: prepareSeqAddUninit (seqs_v2.nim:212)
==14663== by 0x10CF6F: raiseExceptionEx (excpt.nim:538)
==14663== by 0x11661F: amain::amainX20X28AsyncX29_(Future<void>) (bug.nim:10)
==14663== ...
==14663==
==14663== 136 (80 direct, 56 indirect) bytes in 1 blocks are definitely lost in loss record 2 of 2
==14663== at 0x48850C8: malloc (vg_replace_malloc.c:381)
==14663== by 0x10C8E3: nimNewObj (arc.nim:122)
==14663== by 0x115403: err::errX20X28AsyncX29_(Future<void>) (asyncmacro.nim:274)
==14663== by 0x116027: err::errNimAsyncContinue(Future<void>, ClosureIt<void>) (asyncmacro.nim:44)
==14663== by 0x1163D3: bug::err (bug.nim:3)
==14663== ...
==14663==
==14663== LEAK SUMMARY:
==14663== definitely lost: 80 bytes in 1 blocks
==14663== indirectly lost: 56 bytes in 1 blocks
==14663== possibly lost: 0 bytes in 0 blocks
==14663== still reachable: 0 bytes in 0 blocks
==14663== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
```
After (this PR):
```
==14675== HEAP SUMMARY:
==14675== in use at exit: 0 bytes in 0 blocks
==14675== total heap usage: 22 allocs, 22 frees, 116,466 bytes allocated
==14675==
==14675== All heap blocks were freed -- no leaks are possible
==14675==
==14675== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
```
## Testing
- New `tests/async/t23615.nim` (modeled on `t23212.nim`: `valgrind:
true` + alloc-stats assertion) covers both the pure closure-iterator
form and the async form from the issue, with the caught exception looped
50x so the leak blows well past the slack threshold. It passes with this
PR and fails against devel.
- Testament categories `async`, `arc`, `iter`, `exception` all pass with
the patched compiler (323 tests).
- Behavior is unchanged on a sanity program covering multi-branch
dispatch, `as e` binding, nested try, and re-raise across yields: output
is byte-identical to devel; the patched build just frees 2 more blocks
per caught exception.
## Summary
Adds `--genBif:on|off`, allowing regular compiler builds to generate
per-module semantic BIF artifacts in `nimcache`.
This reuses the semantic artifact format produced by incremental
compilation without enabling IC or changing the normal code-generation
and linking pipeline.
In comparison to `nim check --compress ...` this new flag `nim c
--genBif:on --compileOnly yourlib.nim` is considerably more useful for
tooling.
That produced full semantic proc declarations, Nim visibility,
signatures, overload disambiguators, and pragmas. For a proc that was
actually code-generated, it also recorded the exact backend name, for
example.
## Motivation
External tools such as language servers, debuggers, and binding
generators can benefit from resolved symbol and type information
produced during an ordinary build. Previously, these semantic BIF
artifacts were tied to the incremental compiler workflow.
## Details
With the option enabled:
```sh
nim c --genBif:on project.nim
```
the compiler writes semantic `.s.bif` files and their supporting
sidecars for each semantically checked module while continuing with the
requested backend normally.
The option:
- Works with non-IC builds.
- Does not enable incremental compilation.
- Does not change generated program behavior.
- Does not enable or introduce native ABI exports.
- Does not generate `.abi.nif` manifests.
- Is ignored for NimScript compilation.
The `genBif` name follows existing artifact-generation options such as
`genScript`, `genMapping`, and `genCDeps`.
## Testing
Added a focused C backend test that runs a regular build with
`--genBif:on` and verifies that semantic `.s.bif` artifacts are
generated.
A release-mode temporary compiler build and the focused Testament test
both pass.
…pile time
fixes#26000
vm: preserve lvalues for mutations of broadcast array elements
Load in-place mutation targets through their address so mutations don't
operate on detached copies of broadcast defaults. This also preserves
nested lvalues and evaluates indexed destinations only once.
Cover sequence, string, and set mutations through direct, nested, field,
enum-indexed, and range-indexed array elements.
fix#25976
Initialize tagEffects for proc types that declare .forbids but omit
.tags,
so they behave like explicit tags: [] during indirect-call effect
tracking.
Add a regression for the nested callback assignment case.
fixes#25886fixes#25883
See #25883
Tuples only hash leaves so if 2 tuples have the same flattened
representation they collide in the C codegen.
Fix by hashing the length as well to disambiguate nesting levels.
---------
Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>
fix#25608
This pull request improves how the compiler handles warnings for
implicit range conversions, ensuring that only non-constant values
trigger downsizing warnings. It also adds new test cases to verify that
assignments and function calls involving compile-time constants do not
produce unnecessary warnings.
Improvements to range conversion warnings:
* Updated the logic in `compiler/sempass2.nim` to skip implicit range
conversion warnings for compile-time constants by checking if an
expression is constant with `getConstExpr`. Now, only non-constant
values will trigger the warning.
Testing enhancements:
* Added new test cases in `tests/range/timplicitrangedownsizing.nim` to
confirm that assignments and function calls with constant enum and
integer values do not trigger downsizing warnings.
Explicit `=sink` calls such as `Isolated[T].=sink` can delegate to a
field type like `float`, which has no attached sink op. In that case
`replaceHookMagic` leaves the builtin `mAsgn` call in place.
`genMagicExpr` did not lower that shape, which caused the regression.
Mapping `=sink` to `nkSinkAsgn` and other builtin assignment hooks to
`nkAsgn`.
fixes#25803
This pull request introduces a new approach for generating C++
constructor expressions in the Nim compiler's C++ backend, ensuring that
type-prefixed construction is used when needed (such as in assignments),
rather than just braced initializer lists. It also adds a new test case
(with corresponding C++ header) to verify correct behavior when
assigning to types with overloaded assignment operators and
constructors.
**C++ code generation improvements:**
* Added `genCppConstructorExpr` in `ccgtypes.nim`, which generates a
full type-prefixed constructor expression (e.g., `Foo(a, b)`) for C++
code generation, as opposed to just a braced initializer list. This is
important for contexts like assignments where the type must be explicit.
* Updated `resetLoc` in `cgen.nim` to use `genCppConstructorExpr`
instead of `genCppInitializer` when initializing imported C++ types,
ensuring correct code generation for assignments.
**Testing:**
* Added a new C++ header file, `tcpp_default_ctor_assignment.h`,
defining a struct `AmbiguousAssign` with overloaded assignment operators
and constructors to test ambiguous assignment scenarios.
* Added a corresponding Nim test, `tcpp_default_ctor_assignment.nim`,
which exercises construction and assignment for the imported C++ type,
ensuring the new code generation logic works as intended.
fixes#25945
When `@[]` appears inside a nested `if` expression that also contains
statements, the AST wraps it in `nkStmtListExpr` nodes. The empty
container's `tyEmpty` element type was never resolved to a concrete
type, causing the C codegen to ICE with "cannot map the empty seq type
to a C type".
Walk through nested statement-list/block expressions in
`fitNodePostMatch` to find the innermost value node and propagate the
formal type to empty containers.
fixes#25949
track still walks both branches of preserved when nimvm, but it now sets
a small inNimvmBranch flag while visiting the VM branch, and trackCall
skips sfCompileTime marking only when that flag is set.
