[clang] [-Wunsafe-buffer-usage] Suppress warning when 2-D constant arrays are indexed (PR #118249)
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Sun Dec 1 20:58:45 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-analysis
Author: Malavika Samak (malavikasamak)
<details>
<summary>Changes</summary>
Do not warn about unsafe buffer access, when 2-D constant arrays are accessed and the indices are within the bounds of the buffer. Warning in such cases is a false postive. Such a suppression aleady exists for 1-d arrays and it is now extended to 2-D arrays.
(rdar://137926311)
---
Full diff: https://github.com/llvm/llvm-project/pull/118249.diff
5 Files Affected:
- (modified) clang/lib/Analysis/UnsafeBufferUsage.cpp (+49-15)
- (modified) clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp (+6)
- (modified) clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-main.cpp (+1-2)
- (modified) clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-unsupported.cpp (+1-1)
- (modified) clang/test/SemaCXX/warn-unsafe-buffer-usage.cpp (+11-22)
``````````diff
diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 5f36ffa926b269..f1e3b28fc03249 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -433,20 +433,56 @@ AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
// already duplicated
// - call both from Sema and from here
- const auto *BaseDRE =
+ auto CheckBounds = [](const ArraySubscriptExpr *ASE, uint64_t limit) -> bool {
+ if (const auto *IdxLit = dyn_cast<IntegerLiteral>(ASE->getIdx())) {
+ const APInt ArrIdx = IdxLit->getValue();
+ if (ArrIdx.isNonNegative() && ArrIdx.getLimitedValue() < limit)
+ return true;
+ }
+ return false;
+ };
+
+ const auto *BaseASE =
+ dyn_cast<ArraySubscriptExpr>(Node.getBase()->IgnoreParenImpCasts());
+ uint64_t size = 0;
+
+ if (BaseASE) {
+ const auto *DRE =
+ dyn_cast<DeclRefExpr>(BaseASE->getBase()->IgnoreParenImpCasts());
+
+ if (!DRE)
+ return false;
+
+ const auto *CATy = dyn_cast<ConstantArrayType>(
+ DRE->getType()->getUnqualifiedDesugaredType());
+ if (!CATy) {
+ return false;
+ }
+ size = CATy->getLimitedSize();
+
+ if (!CheckBounds(BaseASE, size))
+ return false;
+
+ CATy = Finder->getASTContext().getAsConstantArrayType(BaseASE->getType());
+ if (!CATy) {
+ return false;
+ }
+
+ size = CATy->getLimitedSize();
+ return CheckBounds(&Node, size);
+ }
+
+ const DeclRefExpr *BaseDRE =
dyn_cast<DeclRefExpr>(Node.getBase()->IgnoreParenImpCasts());
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());
+ const auto *CATy =
+ Finder->getASTContext().getAsConstantArrayType(BaseDRE->getType());
if (!CATy) {
return false;
}
@@ -455,15 +491,7 @@ AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
size = SLiteral->getLength() + 1;
}
- 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() < size)
- return true;
- }
-
- return false;
+ return CheckBounds(&Node, size);
}
AST_MATCHER_P(CallExpr, hasNumArgs, unsigned, Num) {
@@ -1172,6 +1200,12 @@ class ArraySubscriptGadget : public WarningGadget {
if (const auto *DRE =
dyn_cast<DeclRefExpr>(ASE->getBase()->IgnoreParenImpCasts())) {
return {DRE};
+ } else if (const auto *BaseASE = dyn_cast<ArraySubscriptExpr>(
+ ASE->getBase()->IgnoreParenImpCasts())) {
+ if (const auto *DRE = dyn_cast<DeclRefExpr>(
+ BaseASE->getBase()->IgnoreParenImpCasts())) {
+ return {DRE};
+ }
}
return {};
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
index c6c93a27e4b969..41cdc122b7d2fa 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp
@@ -52,3 +52,9 @@ void constant_id_string(unsigned idx) {
unsafe_char = ""[1]; //expected-warning{{unsafe buffer access}}
unsafe_char = ""[idx]; //expected-warning{{unsafe buffer access}}
}
+
+typedef float Float4x4[4][4];
+
+float multi_dimension_array(Float4x4& matrix) {
+ return matrix[1][1];
+}
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-main.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-main.cpp
index c6b095031e0e32..d1fd1c00a9ea34 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-main.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-main.cpp
@@ -8,6 +8,5 @@
// main function
int main(int argc, char *argv[]) { // expected-warning{{'argv' is an unsafe pointer used for buffer access}}
char tmp;
- tmp = argv[5][5]; // expected-note{{used in buffer access here}} \
- expected-warning{{unsafe buffer access}}
+ tmp = argv[5][5]; // expected-note2{{used in buffer access here}}
}
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-unsupported.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-unsupported.cpp
index 71350098613d19..5b22a5c5f8acfb 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-unsupported.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-parm-unsupported.cpp
@@ -118,7 +118,7 @@ void isArrayDecayToPointerUPC(int a[][10], int (*b)[10]) {
// expected-warning at -2{{'b' is an unsafe pointer used for buffer access}}
int tmp;
- tmp = a[5][5] + b[5][5]; // expected-warning2{{unsafe buffer access}} expected-note2{{used in buffer access here}}
+ tmp = a[5][5] + b[5][5]; // expected-note4{{used in buffer access here}}
}
// parameter having default values:
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage.cpp
index 642db0e9d3c632..5d75aa66a0781f 100644
--- a/clang/test/SemaCXX/warn-unsafe-buffer-usage.cpp
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage.cpp
@@ -40,12 +40,9 @@ void testArraySubscripts(int idx, int *p, int **pp) {
// expected-warning at -1{{'p' is an unsafe pointer used for buffer access}}
// expected-warning at -2{{'pp' is an unsafe pointer used for buffer access}}
foo(p[1], // expected-note{{used in buffer access here}}
- pp[1][1], // expected-note{{used in buffer access here}}
- // expected-warning at -1{{unsafe buffer access}}
- 1[1[pp]], // expected-note{{used in buffer access here}}
- // expected-warning at -1{{unsafe buffer access}}
- 1[pp][1] // expected-note{{used in buffer access here}}
- // expected-warning at -1{{unsafe buffer access}}
+ pp[1][1], // expected-note2{{used in buffer access here}}
+ 1[1[pp]], // expected-note2{{used in buffer access here}}
+ 1[pp][1] // expected-note2{{used in buffer access here}}
);
if (p[3]) { // expected-note{{used in buffer access here}}
@@ -65,13 +62,9 @@ void testArraySubscripts(int idx, int *p, int **pp) {
int b[10][10]; // expected-warning{{'b' is an unsafe buffer that does not perform bounds checks}}
foo(a[idx], idx[a], // expected-note2{{used in buffer access here}}
- b[idx][idx + 1], // expected-warning{{unsafe buffer access}}
- // expected-note at -1{{used in buffer access here}}
- (idx + 1)[b][idx],// expected-warning{{unsafe buffer access}}
- // expected-note at -1{{used in buffer access here}}
- (idx + 1)[idx[b]]);
- // expected-warning at -1{{unsafe buffer access}}
- // expected-note at -2{{used in buffer access here}}
+ b[idx][idx + 1], // expected-note2{{used in buffer access here}}
+ (idx + 1)[b][idx],// expected-note2{{used in buffer access here}}
+ (idx + 1)[idx[b]]); // expected-note2{{used in buffer access here}}
// Not to warn when index is zero
foo(p[0], pp[0][0], 0[0[pp]], 0[pp][0],
@@ -108,8 +101,7 @@ void testQualifiedParameters(const int * p, const int * const q, const int a[10]
foo(p[1], 1[p], p[-1], // expected-note3{{used in buffer access here}}
q[1], 1[q], q[-1], // expected-note3{{used in buffer access here}}
a[1], // expected-note{{used in buffer access here}} `a` is of pointer type
- b[1][2] // expected-note{{used in buffer access here}} `b[1]` is of array type
- // expected-warning at -1{{unsafe buffer access}}
+ b[1][2] // expected-note2{{used in buffer access here}} `b[1]` is of array type
);
}
@@ -223,10 +215,9 @@ template<typename T, int N> T f(T t, T * pt, T a[N], T (&b)[N]) {
// expected-warning at -1{{'t' is an unsafe pointer used for buffer access}}
// expected-warning at -2{{'pt' is an unsafe pointer used for buffer access}}
// expected-warning at -3{{'a' is an unsafe pointer used for buffer access}}
- // expected-warning at -4{{'b' is an unsafe buffer that does not perform bounds checks}}
foo(pt[1], // expected-note{{used in buffer access here}}
a[1], // expected-note{{used in buffer access here}}
- b[1]); // expected-note{{used in buffer access here}}
+ b[1]);
return &t[1]; // expected-note{{used in buffer access here}}
}
@@ -366,17 +357,15 @@ int testArrayAccesses(int n, int idx) {
// expected-warning at -1{{'cArr' is an unsafe buffer that does not perform bounds checks}}
int d = cArr[0][0];
foo(cArr[0][0]);
- foo(cArr[idx][idx + 1]); // expected-note{{used in buffer access here}}
- // expected-warning at -1{{unsafe buffer access}}
- auto cPtr = cArr[idx][idx * 2]; // expected-note{{used in buffer access here}}
- // expected-warning at -1{{unsafe buffer access}}
+ foo(cArr[idx][idx + 1]); // expected-note2{{used in buffer access here}}
+ auto cPtr = cArr[idx][idx * 2]; // expected-note2{{used in buffer access here}}
foo(cPtr);
// Typdefs
typedef int A[3];
const A tArr = {4, 5, 6};
foo(tArr[0], tArr[1]);
- return cArr[0][1]; // expected-warning{{unsafe buffer access}}
+ return cArr[0][1];
}
void testArrayPtrArithmetic(int x[]) { // expected-warning{{'x' is an unsafe pointer used for buffer access}}
``````````
</details>
https://github.com/llvm/llvm-project/pull/118249
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