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19d09b59f8
ref https://github.com/nim-lang/Nim/issues/25849
The important part is in compiler/vmgen.nim:1838: when the VM lowers
a[i] or a.b as an address-producing operation, it emits opcLdArrAddr /
opcLdObjAddr. That returns an alias into the storage owned by the source
register. Before the patch, that source register could still betreated
as a normal temporary and later reclaimed or reused by the allocator.
Once that happened, the address result was still live, but the backing
temp was no longer guaranteed to exist, which is what led to the
nil/illegal-storage crash.
The fix is to pin that source temp by changing its slot kind to
slotTempPerm right after emitting the address load. You can see the same
lifetime rule already existed for the generic addr(...) path around
compiler/vmgen.nim:1551: if the source is a temporary and we take its
address, the compiler marks it permanent so freeTemp won’t recycle it.
The patch extends that exact rule to array and object address loads:
- compiler/vmgen.nim:1843
- compiler/vmgen.nim:1861
slotTempPerm is outside the normal freeTemp range in
compiler/vmgen.nim:248, so once a temp is upgraded to permanent, the VM
allocator stops treating it as reusable. That is the actual root-cause
fix: it preserves the backing storage for the address result until the
surrounding evaluation is done.
The regression test in tests/vm/t25849.nim:8 forces exactly that path
with a local lent iterator over an array and a static VM evaluation.
(cherry picked from commit 4b374eb0a6)
This directory contains the test cases.
Each test must have a filename of the form: t*.nim
Note: Testament is only aware of tests under a directory (eg tests/foo/) and will ignore
top-level tests like tests/tbar.nim.
Specs
Each test can contain a spec in a discard """ ... """ block.
Check out the parseSpec procedure in the specs module for a full and reliable reference
action
Specifies what action this test should take.
Default: run
Options:
compile- compiles the module and fails the test if compilations fails.run- compiles and runs the module, fails the test if compilation or execution of test code fails.reject- compiles the module and fails the test if compilation succeeds.
There are certain spec keys that imply run, including output and
outputsub.
Categories
Each folder under this directory represents a test category, which can be
tested by running koch tests pcat <category> (or cat to avoid parallel
testing, which is slower).
The folder dll contains simple DLL tests.
The folder realtimeGC contains a test for validating that the realtime GC
can run properly without linking against the nimrtl.dll/so.