runtime: preserve recover error values

[cpunion]

Summary

• Panic with runtime error values instead of plain strings so recover() values assert to error and runtime.Error.
• Build TypeAssertionError values for compiler-generated failed type assertions, and fix slice-to-array conversion panic bounds order.
• Preserve direct recover semantics through compiler-generated method wrappers when the wrapper is itself the deferred call, while keeping nested wrapper calls non-recovering.
• Preserve Go 1.26 embedded method-wrapper function pointer semantics for fixedbugs/issue73917.go and fixedbugs/issue73920.go: a recover in a real helper call reached through deferred promoted wrappers remains indirect, and the outer deferred recover still sees the panic.
• Preserve local values across fault-triggered longjmp recovery by emitting volatile loads/stores for local SSA allocs in functions with recover blocks.
• Add focused test/go coverage for recovered runtime errors, type assertion panic values, method-wrapper recover semantics, embedded wrapper function-pointer recover semantics, and fault recovery preserving named results; remove the now-passing recover2.go, zerodivide.go, recover4.go, fixedbugs/issue73917.go, and fixedbugs/issue73920.go GOROOT xfails.

Still XFail / Out of Scope

• recover.go remains xfail in this PR. On this branch it still fails before the recover-10 path with the ssa: panic with runtime type assertion errors #1892 interface type identity issue: interface conversion: interface {} is func(*main.T1), not func(*main.T1) (types from different scopes).
• This PR does not cherry-pick ssa: panic with runtime type assertion errors #1892. The recover-wrapper behavior exposed by missing recover 10 is covered independently by test/go.
• The new embedded-wrapper test/go cases are Go 1.26+ semantic coverage. Go 1.24 has pre-Go 1.26 behavior for the upstream issue73917.go/issue73920.go programs, so those local tests skip under Go <1.26.
• A full Go 1.26 standard-library run of test/go currently hits unrelated nil/range behavior in TestRangeOverNilArrayPointerCallIsEvaluated; this PR intentionally does not cover nil/range, chan, print, interface, reflect, GC, liveness, finalizer, or goroutine domains.

Testing

• go test ./test/go -run 'TestRecoverThrough|TestRecoverAfterFault' -count=1
• go run ./cmd/llgo test -run 'TestRecoverThrough|TestRecoverAfterFault' -count=1 ./test/go
• go test ./test/goroot -run TestGoRootRunCases/recover4.go -count=1 -args -goroot "$(go env GOROOT)" -dirs . -case '^recover4\.go$' -xfail /tmp/llgo-empty-xfail.yaml
• go test ./test/goroot -run TestGoRootRunCases/recover4.go -count=1 -args -goroot "$(go env GOROOT)" -dirs . -case '^recover4\.go$'
• go test ./test/goroot -run TestGoRootRunCases/recover.go -count=1 -args -goroot "$(go env GOROOT)" -dirs . -case '^recover\.go$' (passes via retained xfail)
• go test ./test/goroot -run TestGoRootRunCases/recover.go -count=1 -args -goroot "$(go env GOROOT)" -dirs . -case '^recover\.go$' -xfail /tmp/llgo-empty-xfail.yaml (expected failure: ssa: panic with runtime type assertion errors #1892 interface type identity blocker)
• go test ./test/go -run 'TestDeferredEmbedded.*MethodWrapperKeepsIndirectRecoverNil|TestRecoverThrough' -count=1
• /Users/lijie/sdk/go1.26.0/bin/go test ./test/go -run 'TestDeferredEmbedded.*MethodWrapperKeepsIndirectRecoverNil' -count=1 -v
• /Users/lijie/sdk/go1.26.0/bin/go run ./cmd/llgo test -run 'TestDeferredEmbedded.*MethodWrapperKeepsIndirectRecoverNil|TestRecoverThrough' -count=1 ./test/go
• go test ./test/goroot -run TestGoRootRunCases -count=1 -args -goroot /Users/lijie/sdk/go1.26.0 -dirs fixedbugs -case '^fixedbugs/issue739(17|20)\.go$'
• go test ./test/go -count=1
• (cd runtime && go test ./internal/runtime -count=1)
• go test ./ssa -count=1
• go test ./cl -count=1
• /Users/lijie/sdk/go1.26.0/bin/go test ./test/go -count=1 (known unrelated failure: TestRangeOverNilArrayPointerCallIsEvaluated nil array pointer range SIGSEGV)

GOROOT CI

Full GOROOT CI is disabled/too slow for regular PR validation in this repo and the GOROOT workflow is manual-only. This PR keeps stable coverage in test/go and lists the exact targeted GOROOT commands above. I will monitor the available PR checks after pushing the fork head branch; I will not push branches to xgo-dev/llgo.

[cpunion]

CI note: normal PR CI is running from the fork branch cpunion:codex/goroot-panic-coverage.

I attempted to dispatch the manual-only GOROOT workflow for the PR head branch, but GitHub rejected the upstream dispatch because the ref only exists on the fork:

HTTP 422: No ref found for: codex/goroot-panic-coverage

I also attempted to dispatch .github/workflows/goroot.yml on cpunion/llgo at the fork branch, but GitHub returned:

HTTP 404: workflow .github/workflows/goroot.yml not found on the default branch

Per branch policy, I did not push an upstream xgo-dev/llgo ref. Local targeted GOROOT commands are listed in the PR body.

[cpunion]

Updated PR after rebasing onto current xgo-dev/main and adjusted the new genericembediface FileCheck expectation for the runtime.TypeAssertError path introduced by this branch.

Additional tests run locally:

• go test ./cl ./ssa -run 'TestRunAndTestFromTestgo/genericembediface|TestFromTestgo/genericembediface' -count=1
• go test ./test/go -run 'TestRecoveredRuntimePanicsAreErrors|TestRecoveredTypeAssertionPanicsAreRuntimeErrors' -count=1
• go test ./test/goroot -run TestGoRootRunCases -count=1 -timeout=10m -args -goroot "$(go env GOROOT)" -dirs . -case '^(recover2|zerodivide)\.go$' -run-timeout=60s -build-timeout=3m
• git diff --check

The earlier Ubuntu gpg: no valid OpenPGP data found failure occurred during dependency setup before repository tests ran, so the new push should trigger regular PR CI again from the fork branch.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 80.67227% with 23 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ssa/eh.go	70.45%	12 Missing and 1 partial ⚠️
cl/instr.go	54.54%	8 Missing and 2 partials ⚠️

📢 Thoughts on this report? Let us know!

[cpunion]

Update from commit 6b65c2c:\n\n- Fixed direct vs indirect recover scoping and nested panic stack handling; removed the recover1.go xfail entries covered by this PR.\n- Kept recover.go xfails: the remaining failure is reflect/interface type identity in test9reflect2, not the recover/defer panic root.\n- Kept recover4.go xfails: SIGBUS is now routed to the panic path, but the remaining mismatch is stale local/named-result state after fault recovery (memcopy returned 0 vs 131067), which I am not mixing into this recover/defer PR.\n- Kept deferprint.go and fixedbugs/bug409.go xfails: remaining mismatches are float print exponent formatting (+e+00 vs +e+000).\n\nLocal validation:\n- go test ./test/go -count=1\n- go test ./test/goroot -count=1 -run TestGoRootRunCases -args -goroot $(go env GOROOT) -dirs .,fixedbugs -case '^(recover.go|recover1.go|recover4.go|deferprint.go|fixedbugs/bug409.go)$' -run-timeout=30s\n- go test ./ssa ./cl -count=1\n- cd runtime && go test ./internal/runtime -count=1

[cpunion]

Update after 77ceb09:

• Added focused recover/defer coverage in test/go for deferred method wrappers and direct-defer recover semantics.
• Added fault recover coverage for preserving a named result after a protected-memory fault path.
• Fixed recover-frame forwarding through recover-transparent wrappers and made recover-function local alloc loads/stores volatile so fault longjmp keeps observable locals.
• Removed the recover4.go goroot xfails now that it passes independently on this branch.
• Kept recover.go xfail: without ssa: panic with runtime type assertion errors #1892 it still stops first on the interface type-identity panic, so this PR does not cherry-pick the interface fix. The recover-wrapper behavior is covered independently in test/go.

Focused tests passed locally: test/go recover cases via Go and llgo, recover4.go goroot with and without xfail, recover.go goroot with retained xfail, go test ./test/go, go test ./ssa, go test ./cl, and runtime/internal/runtime inside the runtime module.

[cpunion]

Update for commit 66a820936f3baab3164393d63f95d944fd9566fb:

• Classified fixedbugs/issue73917.go and fixedbugs/issue73920.go as Go 1.26 embedded method-wrapper function-pointer defer/recover semantics. Both are in the same recover/defer wrapper scope as this PR.
• Added test/go coverage for value and pointer promoted method wrappers reached through function pointers, keeping the helper recover indirect so the outer deferred recover still receives the panic.
• Removed the now-passing Go 1.26 xfails for both cases on darwin/arm64 and linux/amd64.
• Left nil/range, interface ssa: panic with runtime type assertion errors #1892, GC/liveness/finalizer/goroutine, chan, print, reflect, and related non-wrapper domains untouched.

Focused checks passed:

• go test ./test/goroot -run TestGoRootRunCases -count=1 -args -goroot /Users/lijie/sdk/go1.26.0 -dirs fixedbugs -case '^fixedbugs/issue739(17|20)\.go$'
• /Users/lijie/sdk/go1.26.0/bin/go test ./test/go -run 'TestDeferredEmbedded.*MethodWrapperKeepsIndirectRecoverNil' -count=1 -v
• /Users/lijie/sdk/go1.26.0/bin/go run ./cmd/llgo test -run 'TestDeferredEmbedded.*MethodWrapperKeepsIndirectRecoverNil|TestRecoverThrough' -count=1 ./test/go
• go test ./test/go -count=1
• (cd runtime && go test ./internal/runtime -count=1)
• go test ./ssa -count=1
• go test ./cl -count=1

Known unrelated non-covered check: /Users/lijie/sdk/go1.26.0/bin/go test ./test/go -count=1 fails in TestRangeOverNilArrayPointerCallIsEvaluated with a nil array pointer range SIGSEGV, which is outside this recover/defer wrapper PR.

[cpunion]

Update for fixedbugs/issue43835.go at 5fc53956f98a7718eab8399fd905756b7f058ece:

• Classified as the same recover/defer/named-result-after-panic family: the nil deref is only the panic trigger; after deferred recover, partial true writes from an unfinished assignment/return must not be observed.
• Implemented a compiler-side ordering fix for recover-capable functions: explicit nil-deref assertion before deref loads that could otherwise be eliminated/moved past result writes; existing volatile result-slot handling remains scoped to recover blocks.
• Added stable test/go coverage for assignment, unnamed return, and named return expression forms.
• Removed only the now-covered fixedbugs/issue43835.go xfails for darwin/arm64 and linux/amd64. No GC/liveness/finalizer/goroutine, chan, print, interface, or broader nil-domain changes are included.

Local validation:

• go test ./test/goroot -run TestGoRootRunCases -count=1 -timeout 30m -args -goroot /Users/lijie/sdk/go1.26.0 -dirs fixedbugs -case '^fixedbugs/issue43835\\.go$' -directive-mode runlike -run-timeout 2m\n- go test ./test/go -count=1\n- go test ./ssa -count=1\n- go test ./cl -count=1\n\nRuntime package tests were not rerun for this increment because no runtime code changed.