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[-Wunsafe-buffer-usage] Fix false positives for string literals #115554

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[-Wunsafe-buffer-usage] Fix false positives for string literals #115554

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26 changes: 16 additions & 10 deletions clang/lib/Analysis/UnsafeBufferUsage.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -434,16 +434,22 @@ AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
// already duplicated
// - call both from Sema and from here

const auto *BaseDRE =
dyn_cast<DeclRefExpr>(Node.getBase()->IgnoreParenImpCasts());
if (!BaseDRE)
return false;
if (!BaseDRE->getDecl())
return false;
const auto *CATy = Finder->getASTContext().getAsConstantArrayType(
BaseDRE->getDecl()->getType());
if (!CATy)
return false;
APInt ArrSize{};
if (const auto *BaseDRE =
dyn_cast<DeclRefExpr>(Node.getBase()->IgnoreParenImpCasts())) {
if (!BaseDRE)
return false;
if (!BaseDRE->getDecl())
return false;
const auto *CATy = Finder->getASTContext().getAsConstantArrayType(
BaseDRE->getDecl()->getType());
if (!CATy)
return false;
ArrSize = CATy->getSize();
} else if (const auto *BaseStrLit = dyn_cast<StringLiteral>(Node.getBase()->IgnoreParenImpCasts())) {
// Add 1 for the terminating null character.
ArrSize = APInt{64, BaseStrLit->getLength() + 1, false};
}

if (const auto *IdxLit = dyn_cast<IntegerLiteral>(Node.getIdx())) {
const APInt ArrIdx = IdxLit->getValue();
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18 changes: 18 additions & 0 deletions clang/test/SemaCXX/warn-unsafe-buffer-usage-string-literal.cpp
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
// RUN: %clang_cc1 -std=c++20 -Wno-everything -Wunsafe-buffer-usage \
// RUN: -fsafe-buffer-usage-suggestions \
// RUN: -verify %s

// CHECK-NOT: [-Wunsafe-buffer-usage]


void foo(unsigned idx) {
char c = '0';
c = "abc"[0];
c = "abc"[1];
c = "abc"[2];
c = "abc"[3];
c = "abc"[4]; // expected-warning{{unsafe buffer access}}
c = "abc"[idx]; // expected-warning{{unsafe buffer access}}
c = ""[0];
c = ""[1]; // expected-warning{{unsafe buffer access}}
}
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