[Wunsafe-buffer-usage] Fix false positives in handling string literals. #115552
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@llvm/pr-subscribers-clang-analysis @llvm/pr-subscribers-clang Author: Malavika Samak (malavikasamak) ChangesDo not warn when a string literal is indexed and the idex value is within the bounds of the length of the string. (rdar://139106996) Full diff: https://github.com/llvm/llvm-project/pull/115552.diff 2 Files Affected:
diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 2c68409b846bc8..650d51bebd66f7 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())
+ ArrIdx.getLimitedValue() < size)
return true;
}
@@ -1142,7 +1152,7 @@ class ArraySubscriptGadget : public WarningGadget {
// clang-format off
return stmt(arraySubscriptExpr(
hasBase(ignoringParenImpCasts(
- anyOf(hasPointerType(), hasArrayType()))),
+ anyOf(hasPointerType(), hasArrayType(), stringLiteral()))),
unless(anyOf(
isSafeArraySubscript(),
hasIndex(
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
index 8b2f103ec66708..0a443543d3f604 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
@@ -38,3 +38,10 @@ 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() {
+ char safe_char = "abc"[1]; // no-warning
+ char abcd[5] = "abc";
+ abcd[2]; // no-warning
+ safe_char = "abc"[3]; //expected-warning{{unsafe buffer access}}
+}
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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| 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}} |
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This shouldn't be a warning either.
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In this case, I think we should warn, as the length here including the null terminator is 1.
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Sorry, my bad. You're right
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)
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…s. (llvm#115552) 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) Co-authored-by: MalavikaSamak <[email protected]>
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…s. (llvm#115552) 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) Co-authored-by: MalavikaSamak <[email protected]> (cherry picked from commit da032a6)
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…terals [Cherry-Pick][Wunsafe-buffer-usage] Fix false positives in handling string literals. (llvm#115552)
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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)