https://github.com/steakhal created
https://github.com/llvm/llvm-project/pull/70837
Workaround the case when the `this` pointer is actually a `NonLoc`, by
returning `Unknown` instead.
The solution isn't ideal, as `this` should be really a `Loc`, but due to how
casts work, I feel this is our easiest and best option.
I've considered using `SVB.evalCast(ThisVal, Base->getType(), QualType())`, but
it doesn't work as `EvalCastVisitor::VisitNonLocSymbolVal()` only evaluates
casts that happen from NonLoc to NonLocs.
When I tried to actually implement that case, I figured:
1) Create a SymbolicRegion from that nonloc::SymbolVal; but SymbolRegion ctor
expects a pointer type for the symbol.
2) Okay, just have a SymbolCast, getting us the pointer type; but SymbolRegion
expects SymbolData symbols, not generic SymExprs, as stated:
> // Because pointer arithmetic is represented by ElementRegion layers,
> // the base symbol here should not contain any arithmetic.
3) We can't use ElementRegions to perform this cast because to have an
ElementRegion, you already have to have a SubRegion that you want to cast, but
the point is that we don't have that.
At this point, I gave up, and just returned `Unknown` xD IMO this is still
better than having a crash.
Fixes #69922
>From a7f64815f4986fad597b9cb2d1acce2de9ac20bf Mon Sep 17 00:00:00 2001
From: Balazs Benics <benicsbal...@gmail.com>
Date: Mon, 23 Oct 2023 18:10:29 +0200
Subject: [PATCH] [analyzer] Fix assertion failure in
CXXInstanceCall::getCXXThisVal
Workaround the case when the `this` pointer is actually a `NonLoc`, by
returning `Unknown` instead.
The solution isn't ideal, as `this` should be really a `Loc`, but due to
how casts work, I feel this is our easiest and best option.
I've considered using `SVB.evalCast(ThisVal, Base->getType(), QualType())`,
but it doesn't work as `EvalCastVisitor::VisitNonLocSymbolVal()` only
evaluates casts that happen from NonLoc to NonLocs.
When I tried to actually implement that case, I figured:
1) Create a SymbolicRegion from that nonloc::SymbolVal; but SymbolRegion
ctor expects a pointer type for the symbol.
2) Okay, just have a SymbolCast, getting us the pointer type; but
SymbolRegion expects SymbolData symbols, not generic SymExprs, as stated:
> // Because pointer arithmetic is represented by ElementRegion layers,
> // the base symbol here should not contain any arithmetic.
3) We can't use ElementRegions to perform this cast because to have an
ElementRegion, you already have to have a SubRegion that you want to
cast, but the point is that we don't have that.
At this point, I gave up, and just returned `Unknown` xD
IMO this is still better than having a crash.
Fixes #69922
---
clang/lib/StaticAnalyzer/Core/CallEvent.cpp | 5 ++---
clang/test/Analysis/builtin_bitcast.cpp | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
b/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
index ad5bb66c4fff3c8..20bc64dc2631cec 100644
--- a/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
+++ b/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -715,10 +715,9 @@ void CXXInstanceCall::getExtraInvalidatedValues(
SVal CXXInstanceCall::getCXXThisVal() const {
const Expr *Base = getCXXThisExpr();
// FIXME: This doesn't handle an overloaded ->* operator.
- if (!Base)
+ SVal ThisVal = Base ? getSVal(Base) : UnknownVal();
+ if (isa<NonLoc>(ThisVal))
return UnknownVal();
-
- SVal ThisVal = getSVal(Base);
assert(ThisVal.isUnknownOrUndef() || isa<Loc>(ThisVal));
return ThisVal;
}
diff --git a/clang/test/Analysis/builtin_bitcast.cpp
b/clang/test/Analysis/builtin_bitcast.cpp
index 396e7caa45f6acd..13475694d287a22 100644
--- a/clang/test/Analysis/builtin_bitcast.cpp
+++ b/clang/test/Analysis/builtin_bitcast.cpp
@@ -30,3 +30,24 @@ void test(int i) {
clang_analyzer_dump(g4);
// expected-warning@-1 {{&i [as 64 bit integer]}}
}
+
+struct A {
+ int n;
+ void set(int x) {
+ n = x;
+ }
+};
+using ptr_size = decltype(sizeof(void *));
+void gh_69922(ptr_size p) {
+ // expected-warning-re@+1 {{(reg_${{[0-9]+}}<ptr_size p>) & 1U}}
+ clang_analyzer_dump(__builtin_bit_cast(A*, p & 1));
+
+ __builtin_bit_cast(A*, p & 1)->set(2); // no-crash
+ // However, since the `this` pointer is expected to be a Loc, but we have
+ // NonLoc there, we simply give up and resolve it as `Unknown`.
+ // Then, inside the `set()` member function call we can't evaluate the
+ // store to the member variable `n`.
+
+ clang_analyzer_dump(__builtin_bit_cast(A*, p & 1)->n); // Ideally, this
should print "2".
+ // expected-warning-re@-1 {{(reg_${{[0-9]+}}<ptr_size p>) & 1U}}
+}
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