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[Sema] Fix tautological bounds check warning with -fwrapv #120480

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Merged
merged 3 commits into from
Dec 19, 2024
Merged

[Sema] Fix tautological bounds check warning with -fwrapv #120480

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0eb68a5
[Sema] Fix tautological bounds check warning with -fwrapv
nathanchance Dec 18, 2024
8504a0d
fixup! [Sema] Fix tautological bounds check warning with -fwrapv
nathanchance Dec 18, 2024
6483ce9
fixup! [Sema] Fix tautological bounds check warning with -fwrapv
nathanchance Dec 18, 2024
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7 changes: 4 additions & 3 deletions clang/lib/Sema/SemaExpr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11789,10 +11789,11 @@ static bool checkForArray(const Expr *E) {
/// Detect patterns ptr + size >= ptr and ptr + size < ptr, where ptr is a
/// pointer and size is an unsigned integer. Return whether the result is
/// always true/false.
static std::optional<bool> isTautologicalBoundsCheck(const Expr *LHS,
static std::optional<bool> isTautologicalBoundsCheck(Sema &S, const Expr *LHS,
const Expr *RHS,
BinaryOperatorKind Opc) {
if (!LHS->getType()->isPointerType())
if (!LHS->getType()->isPointerType() ||
S.getLangOpts().isSignedOverflowDefined())
return std::nullopt;

// Canonicalize to >= or < predicate.
Expand Down Expand Up @@ -11940,7 +11941,7 @@ static void diagnoseTautologicalComparison(Sema &S, SourceLocation Loc,
<< 1 /*array comparison*/
<< Result);
} else if (std::optional<bool> Res =
isTautologicalBoundsCheck(LHS, RHS, Opc)) {
isTautologicalBoundsCheck(S, LHS, RHS, Opc)) {
S.DiagRuntimeBehavior(Loc, nullptr,
S.PDiag(diag::warn_comparison_always)
<< 2 /*pointer comparison*/
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3 changes: 3 additions & 0 deletions clang/test/Sema/tautological-pointer-comparison.c
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Original file line number Diff line number Diff line change
@@ -1,4 +1,7 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s
// RUN: %clang_cc1 -fsyntax-only -fwrapv -verify=fwrapv %s

// fwrapv-no-diagnostics

int add_ptr_idx_ult_ptr(const char *ptr, unsigned index) {
return ptr + index < ptr; // expected-warning {{pointer comparison always evaluates to false}}
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