goto-symex: nil array size must not have a type added #5657
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tautschnig
requested review from
kroening,
peterschrammel,
romainbrenguier and
smowton
as code owners
kroening
reviewed
Dec 14, 2020
| @@ -263,6 +263,10 @@ bool check_renaming(const exprt &expr) | |||
| if(to_ssa_expr(expr).get_original_expr().type() != type) | |||
| return true; | |||
| } | |||
| else if(expr.id() == ID_nil) | |||
| { | |||
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Is that still needed after the change in goto_symex_state.cpp?
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This is just the sanity check (when using --validate-ssa-equation) - hopefully it never fails...
kroening
reviewed
Dec 14, 2020
| { | ||
| DATA_CHECK( | ||
| vm, array_type.size() == nil_exprt{}, "array size must be an expression"); | ||
| } |
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The message in that check could be clearer.
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How about the updated message?
Codecov Report
@@ Coverage Diff @@
## develop #5657 +/- ##
============================================
- Coverage 69.41% 32.26% -37.15%
============================================
Files 1243 985 -258
Lines 100612 83606 -17006
============================================
- Hits 69842 26978 -42864
- Misses 30770 56628 +25858
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An expression has a type() member, which the nil irept lacks. Trying to access (in a non-const context) the type() member would thus create it, which in turn means that it no longer compares equal to a nil_exprt. As SSA renaming did access the type() member in such a way, the type of an array without specified size would no longer compare equal to the irept describing the type as generated by the C front-end, which in turn made simplification fail. The problem was surfaced by running cbmc --unwind 2 --pointer-check --bounds-check on c/ldv-linux-4.2-rc1/linux-4.2-rc1.tar.xz-32_7a-drivers--gpu--drm--i915--i915.ko-entry_point.cil.out.i from SV-COMP.
kroening
approved these changes
Dec 14, 2020
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An expression has a type() member, which the nil irept lacks. Trying to
access (in a non-const context) the type() member would thus create it,
which in turn means that it no longer compares equal to a nil_exprt. As
SSA renaming did access the type() member in such a way, the type of an
array without specified size would no longer compare equal to the irept
describing the type as generated by the C front-end, which in turn made
simplification fail.
The problem was surfaced by running cbmc --unwind 2 --pointer-check
--bounds-check on
c/ldv-linux-4.2-rc1/linux-4.2-rc1.tar.xz-32_7a-drivers--gpu--drm--i915--i915.ko-entry_point.cil.out.i
from SV-COMP.