https://github.com/malavikasamak updated
https://github.com/llvm/llvm-project/pull/115552
>From a3f41d4b947739f97adccbcb3dcef0a37f2a508a Mon Sep 17 00:00:00 2001
From: MalavikaSamak <malavi...@apple.com>
Date: Fri, 8 Nov 2024 13:40:20 -0800
Subject: [PATCH] [Wunsafe-buffer-usage] Fix false positives in handling string
literals.
Do not warn when a string literal is indexed and the idex value is within
the bounds of the length of the string.
(rdar://139106996)
---
clang/lib/Analysis/UnsafeBufferUsage.cpp | 28 +++++++++++++------
.../warn-unsafe-buffer-usage-array.cpp | 14 ++++++++++
2 files changed, 33 insertions(+), 9 deletions(-)
diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp
b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 2c68409b846bc8..2b6a67fcff4b39 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -436,21 +436,31 @@ AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
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)
+ const auto *SLiteral =
+ dyn_cast<StringLiteral>(Node.getBase()->IgnoreParenImpCasts());
+ uint64_t size;
+
+ if (!BaseDRE && !SLiteral)
return false;
+ if (BaseDRE) {
+ if (!BaseDRE->getDecl())
+ return false;
+ const auto *CATy = Finder->getASTContext().getAsConstantArrayType(
+ BaseDRE->getDecl()->getType());
+ if (!CATy) {
+ return false;
+ }
+ size = CATy->getLimitedSize();
+ } else if (SLiteral) {
+ size = SLiteral->getLength();
+ }
+
if (const auto *IdxLit = dyn_cast<IntegerLiteral>(Node.getIdx())) {
const APInt ArrIdx = IdxLit->getValue();
// FIXME: ArrIdx.isNegative() we could immediately emit an error as that's
a
// bug
- if (ArrIdx.isNonNegative() &&
- ArrIdx.getLimitedValue() < CATy->getLimitedSize())
+ if (ArrIdx.isNonNegative() && ArrIdx.getLimitedValue() < size)
return true;
}
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
b/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
index 8b2f103ec66708..eddd3ccc9a1bf2 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
@@ -38,3 +38,17 @@ void constant_idx_unsafe(unsigned idx) {
// expected-note@-1{{change type of 'buffer' to
'std::array' to label it for hardening}}
buffer[10] = 0; // expected-note{{used in buffer access here}}
}
+
+void constant_id_string(unsigned idx) {
+ char safe_char = "abc"[1]; // no-warning
+ safe_char = ""[0];
+ safe_char = "\0"[0];
+
+ char abcd[5] = "abc";
+ abcd[2]; // no-warning
+
+ char unsafe_char = "abc"[3]; //expected-warning{{unsafe buffer access}}
+ unsafe_char = "abc"[-1]; //expected-warning{{unsafe buffer access}}
+ unsafe_char = ""[1]; //expected-warning{{unsafe buffer access}}
+ unsafe_char = ""[idx]; //expected-warning{{unsafe buffer access}}
+}
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