[clang] [Clang][counted_by] Use the expr's RecordDecl if available (PR #205903)
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Thu Jun 25 13:10:31 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Bill Wendling (bwendling)
<details>
<summary>Changes</summary>
The counted field could be in nested structs. This can happen when the
Expr is pointing to a field that has a struct type. In that case, we want
to use that struct type for the StructAccessBase visitor. Otherwise, the
visitor would not find the correct struct base Expr.
Fixes: 205652
---
Full diff: https://github.com/llvm/llvm-project/pull/205903.diff
2 Files Affected:
- (modified) clang/lib/CodeGen/CGExpr.cpp (+15-6)
- (added) clang/test/CodeGen/attr-counted-by-nested-structs.c (+127)
``````````diff
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 465a020e38e74..bfe27bebbea9f 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -1204,12 +1204,21 @@ llvm::Value *CodeGenFunction::GetCountedByFieldExprGEP(
// Using getOuterLexicalRecordContext() here would be wrong because it walks
// past named nested structs to the outermost record, causing a crash when a
// struct with a counted_by FAM is defined nested inside another struct.
- const RecordDecl *RD = CountDecl->getParent();
- while (RD->isAnonymousStructOrUnion()) {
- const auto *Parent = dyn_cast<RecordDecl>(RD->getLexicalParent());
- if (!Parent)
- break;
- RD = Parent;
+ //
+ // The Base expression may itself be a pointer to a field of type 'struct'. If
+ // so, then we want to use that as the "base" RecordDecl.
+ QualType Ty = Base->IgnoreParenNoopCasts(getContext())->getType();
+ if (Ty->isPointerType())
+ Ty = Ty->getPointeeType();
+ const RecordDecl *RD = Ty->getAsRecordDecl();
+ if (!RD) {
+ RD = CountDecl->getParent();
+ while (RD->isAnonymousStructOrUnion()) {
+ const auto *Parent = dyn_cast<RecordDecl>(RD->getLexicalParent());
+ if (!Parent)
+ break;
+ RD = Parent;
+ }
}
// Find the base struct expr (i.e. p in p->a.b.c.d).
diff --git a/clang/test/CodeGen/attr-counted-by-nested-structs.c b/clang/test/CodeGen/attr-counted-by-nested-structs.c
new file mode 100644
index 0000000000000..954764fde2c79
--- /dev/null
+++ b/clang/test/CodeGen/attr-counted-by-nested-structs.c
@@ -0,0 +1,127 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 6
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -Wall -fstrict-flex-arrays=3 -emit-llvm -o - %s | FileCheck %s
+
+#if !__has_attribute(counted_by)
+#error "has attribute broken"
+#endif
+
+#define __counted_by(member) __attribute__((__counted_by__(member)))
+#define __bdos(P) __builtin_dynamic_object_size(P, 0)
+
+struct flex {
+ unsigned count;
+ char a; /* force tail padding */
+ char fam[] __counted_by(count);
+};
+
+struct single_nested {
+ int header;
+ struct flex buf;
+};
+
+struct double_nested {
+ int header;
+ struct single_nested buf;
+};
+
+struct triple_nested {
+ int header;
+ struct double_nested buf;
+};
+
+struct quad_nested {
+ int header;
+ struct triple_nested buf;
+};
+
+// CHECK-LABEL: define dso_local i32 @test_size_of_single_nested(
+// CHECK-SAME: ptr noundef [[P:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: [[P_ADDR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT: store ptr [[P]], ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[TMP0:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF:%.*]] = getelementptr inbounds nuw [[STRUCT_SINGLE_NESTED:%.*]], ptr [[TMP0]], i32 0, i32 1
+// CHECK-NEXT: [[TMP1:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF1:%.*]] = getelementptr inbounds nuw [[STRUCT_SINGLE_NESTED]], ptr [[TMP1]], i32 0, i32 1
+// CHECK-NEXT: [[COUNTED_BY_GEP:%.*]] = getelementptr inbounds [[STRUCT_FLEX:%.*]], ptr [[BUF1]], i32 0, i32 0, i32 1, i32 0
+// CHECK-NEXT: [[COUNTED_BY_LOAD:%.*]] = load i32, ptr [[COUNTED_BY_GEP]], align 4
+// CHECK-NEXT: [[COUNT:%.*]] = zext i32 [[COUNTED_BY_LOAD]] to i64
+// CHECK-NEXT: [[FLEXIBLE_ARRAY_MEMBER_SIZE:%.*]] = mul nuw i64 [[COUNT]], 1
+// CHECK-NEXT: [[RESULT:%.*]] = add i64 [[FLEXIBLE_ARRAY_MEMBER_SIZE]], 12
+// CHECK-NEXT: [[TMP2:%.*]] = icmp sgt i64 [[RESULT]], -1
+// CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i64 [[RESULT]], i64 0
+// CHECK-NEXT: [[CONV:%.*]] = trunc i64 [[TMP3]] to i32
+// CHECK-NEXT: ret i32 [[CONV]]
+//
+unsigned test_size_of_single_nested(struct single_nested *p) {
+ return __bdos(&p->buf);
+}
+
+// CHECK-LABEL: define dso_local i32 @test_size_of_double_nested(
+// CHECK-SAME: ptr noundef [[P:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: [[P_ADDR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT: store ptr [[P]], ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[TMP0:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF:%.*]] = getelementptr inbounds nuw [[STRUCT_DOUBLE_NESTED:%.*]], ptr [[TMP0]], i32 0, i32 1
+// CHECK-NEXT: [[TMP1:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF1:%.*]] = getelementptr inbounds nuw [[STRUCT_DOUBLE_NESTED]], ptr [[TMP1]], i32 0, i32 1
+// CHECK-NEXT: [[COUNTED_BY_GEP:%.*]] = getelementptr inbounds [[STRUCT_SINGLE_NESTED:%.*]], ptr [[BUF1]], i32 0, i32 1, i32 0, i32 1, i32 0
+// CHECK-NEXT: [[COUNTED_BY_LOAD:%.*]] = load i32, ptr [[COUNTED_BY_GEP]], align 4
+// CHECK-NEXT: [[COUNT:%.*]] = zext i32 [[COUNTED_BY_LOAD]] to i64
+// CHECK-NEXT: [[FLEXIBLE_ARRAY_MEMBER_SIZE:%.*]] = mul nuw i64 [[COUNT]], 1
+// CHECK-NEXT: [[RESULT:%.*]] = add i64 [[FLEXIBLE_ARRAY_MEMBER_SIZE]], 16
+// CHECK-NEXT: [[TMP2:%.*]] = icmp sgt i64 [[RESULT]], -1
+// CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i64 [[RESULT]], i64 0
+// CHECK-NEXT: [[CONV:%.*]] = trunc i64 [[TMP3]] to i32
+// CHECK-NEXT: ret i32 [[CONV]]
+//
+unsigned test_size_of_double_nested(struct double_nested *p) {
+ return __bdos(&p->buf);
+}
+
+// CHECK-LABEL: define dso_local i32 @test_size_of_triple_nested(
+// CHECK-SAME: ptr noundef [[P:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: [[P_ADDR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT: store ptr [[P]], ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[TMP0:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF:%.*]] = getelementptr inbounds nuw [[STRUCT_TRIPLE_NESTED:%.*]], ptr [[TMP0]], i32 0, i32 1
+// CHECK-NEXT: [[TMP1:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF1:%.*]] = getelementptr inbounds nuw [[STRUCT_TRIPLE_NESTED]], ptr [[TMP1]], i32 0, i32 1
+// CHECK-NEXT: [[COUNTED_BY_GEP:%.*]] = getelementptr inbounds [[STRUCT_DOUBLE_NESTED:%.*]], ptr [[BUF1]], i32 0, i32 1, i32 1, i32 0, i32 1, i32 0
+// CHECK-NEXT: [[COUNTED_BY_LOAD:%.*]] = load i32, ptr [[COUNTED_BY_GEP]], align 4
+// CHECK-NEXT: [[COUNT:%.*]] = zext i32 [[COUNTED_BY_LOAD]] to i64
+// CHECK-NEXT: [[FLEXIBLE_ARRAY_MEMBER_SIZE:%.*]] = mul nuw i64 [[COUNT]], 1
+// CHECK-NEXT: [[RESULT:%.*]] = add i64 [[FLEXIBLE_ARRAY_MEMBER_SIZE]], 20
+// CHECK-NEXT: [[TMP2:%.*]] = icmp sgt i64 [[RESULT]], -1
+// CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i64 [[RESULT]], i64 0
+// CHECK-NEXT: [[CONV:%.*]] = trunc i64 [[TMP3]] to i32
+// CHECK-NEXT: ret i32 [[CONV]]
+//
+unsigned test_size_of_triple_nested(struct triple_nested *p) {
+ return __bdos(&p->buf);
+}
+
+// CHECK-LABEL: define dso_local i32 @test_size_of_quad_nested(
+// CHECK-SAME: ptr noundef [[P:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: [[P_ADDR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT: store ptr [[P]], ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[TMP0:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF:%.*]] = getelementptr inbounds nuw [[STRUCT_QUAD_NESTED:%.*]], ptr [[TMP0]], i32 0, i32 1
+// CHECK-NEXT: [[TMP1:%.*]] = load ptr, ptr [[P_ADDR]], align 8
+// CHECK-NEXT: [[BUF1:%.*]] = getelementptr inbounds nuw [[STRUCT_QUAD_NESTED]], ptr [[TMP1]], i32 0, i32 1
+// CHECK-NEXT: [[COUNTED_BY_GEP:%.*]] = getelementptr inbounds [[STRUCT_TRIPLE_NESTED:%.*]], ptr [[BUF1]], i32 0, i32 1, i32 1, i32 1, i32 0, i32 1, i32 0
+// CHECK-NEXT: [[COUNTED_BY_LOAD:%.*]] = load i32, ptr [[COUNTED_BY_GEP]], align 4
+// CHECK-NEXT: [[COUNT:%.*]] = zext i32 [[COUNTED_BY_LOAD]] to i64
+// CHECK-NEXT: [[FLEXIBLE_ARRAY_MEMBER_SIZE:%.*]] = mul nuw i64 [[COUNT]], 1
+// CHECK-NEXT: [[RESULT:%.*]] = add i64 [[FLEXIBLE_ARRAY_MEMBER_SIZE]], 24
+// CHECK-NEXT: [[TMP2:%.*]] = icmp sgt i64 [[RESULT]], -1
+// CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i64 [[RESULT]], i64 0
+// CHECK-NEXT: [[CONV:%.*]] = trunc i64 [[TMP3]] to i32
+// CHECK-NEXT: ret i32 [[CONV]]
+//
+unsigned test_size_of_quad_nested(struct quad_nested *p) {
+ return __bdos(&p->buf);
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/205903
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