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Fix segfault on infinite recursion in some cases

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This fixes a segfault on infinite function call recursion (rather than
infinite thunk recursion) by tracking the function call depth in
`EvalState`.

Additionally, to avoid printing extremely long stack traces, stack
frames are now deduplicated, with a `(19997 duplicate traces omitted)`
message. This should only really be triggered in infinite recursion
scenarios.

Before:

    $ nix-instantiate --eval --expr '(x: x x) (x: x x)'
    Segmentation fault: 11

After:

    $ nix-instantiate --eval --expr '(x: x x) (x: x x)'
    error: stack overflow

           at «string»:1:14:
                1| (x: x x) (x: x x)
                 |              ^

    $ nix-instantiate --eval --expr '(x: x x) (x: x x)' --show-trace
    error:
           … from call site
             at «string»:1:1:
                1| (x: x x) (x: x x)
                 | ^

           … while calling anonymous lambda
             at «string»:1:2:
                1| (x: x x) (x: x x)
                 |  ^

           … from call site
             at «string»:1:5:
                1| (x: x x) (x: x x)
                 |     ^

           … while calling anonymous lambda
             at «string»:1:11:
                1| (x: x x) (x: x x)
                 |           ^

           … from call site
             at «string»:1:14:
                1| (x: x x) (x: x x)
                 |              ^

           (19997 duplicate traces omitted)

           error: stack overflow
           at «string»:1:14:
                1| (x: x x) (x: x x)
                 |              ^
This commit is contained in:
Rebecca Turner 2023-12-15 11:52:21 -08:00
parent a21c762dab
commit 7434caca05
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12 changed files with 358 additions and 4 deletions
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36
tests/functional/lang/eval-fail-mutual-recursion.nix Normal file
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@ -0,0 +1,36 @@
# Check that stack frame deduplication only affects consecutive intervals, and
# that they are reported independently of any preceding sections, even if
# they're indistinguishable.
#
# In terms of the current implementation, we check that we clear the set of
# "seen frames" after eliding a group of frames.
#
# Suppose we have:
# - 10 frames in a function A
# - 10 frames in a function B
# - 10 frames in a function A
#
# We want to output:
# - a few frames of A (skip the rest)
# - a few frames of B (skip the rest)
# - a few frames of A (skip the rest)
#
# If we implemented this in the naive manner, we'd instead get:
# - a few frames of A (skip the rest)
# - a few frames of B (skip the rest, _and_ skip the remaining frames of A)
let
throwAfterB = recurse: n:
if n > 0
then throwAfterB recurse (n - 1)
else if recurse
then throwAfterA false 10
else throw "Uh oh!";
throwAfterA = recurse: n:
if n > 0
then throwAfterA recurse (n - 1)
else if recurse
then throwAfterB true 10
else throw "Uh oh!";
in
throwAfterA true 10