[clang]Fix Handle structs exceeding 1EB size limit #146032
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@llvm/pr-subscribers-clang Author: kd0608 (Karthikdhondi) ChangesWhen declaring multiple arrays of 1 ExaByte in a struct, the offset can exceed 2EB, causing incorrect struct size reporting (only 1EB). This fix ensures an error is thrown, preventing the generation of incorrect assembly. #60272 Full diff: https://github.com/llvm/llvm-project/pull/146032.diff 4 Files Affected:
diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td
index d2cd86d05d55a..e3be4ab47633d 100644
--- a/clang/include/clang/Basic/DiagnosticASTKinds.td
+++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -999,6 +999,8 @@ def note_module_odr_violation_mismatch_decl_unknown : Note<
"different friend declaration|different function template|different method|"
"different instance variable|different property|another unexpected decl}2">;
+def err_struct_too_large : Error<
+ "structure '%0' is too large, which exceeds maximum allowed size of %1 bytes">;
def remark_sanitize_address_insert_extra_padding_accepted : Remark<
"-fsanitize-address-field-padding applied to %0">, ShowInSystemHeader,
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index aacc079f2521d..f6a4f76bcc7f6 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -3463,6 +3463,13 @@ ASTContext::getASTRecordLayout(const RecordDecl *D) const {
ASTRecordLayouts[D] = NewEntry;
+ constexpr uint64_t MaxStructSizeInBytes = 1ULL << 60;
+ CharUnits StructSize = NewEntry->getSize();
+ if (static_cast<uint64_t>(StructSize.getQuantity()) >= MaxStructSizeInBytes) {
+ getDiagnostics().Report(D->getLocation(), diag::err_struct_too_large)
+ << D->getName() << MaxStructSizeInBytes;
+ }
+
if (getLangOpts().DumpRecordLayouts) {
llvm::outs() << "\n*** Dumping AST Record Layout\n";
DumpRecordLayout(D, llvm::outs(), getLangOpts().DumpRecordLayoutsSimple);
diff --git a/clang/test/AST/absurdly_big_struct.cpp b/clang/test/AST/absurdly_big_struct.cpp
new file mode 100644
index 0000000000000..04ac4d7ef6b74
--- /dev/null
+++ b/clang/test/AST/absurdly_big_struct.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -triple x86_64-linux-gnu
+
+struct a { // expected-error {{structure 'a' is too large, which exceeds maximum allowed size of 1152921504606846976 bytes}}
+ char x[1ull<<60];
+ char x2[1ull<<60];
+};
+
+a z[1];
+long long x() { return sizeof(a); }
+long long x2() { return sizeof(a::x); }
+long long x3() { return sizeof(a::x2); }
+long long x4() { return sizeof(z); }
diff --git a/clang/test/Sema/offsetof-64.c b/clang/test/Sema/offsetof-64.c
index 8ffc3af985880..692698fe39e00 100644
--- a/clang/test/Sema/offsetof-64.c
+++ b/clang/test/Sema/offsetof-64.c
@@ -2,7 +2,7 @@
// PR15216
// Don't crash when taking computing the offset of structs with large arrays.
-const unsigned long Size = (1l << 60);
+const unsigned long Size = (1l << 58);
struct Chunk1 {
char padding[Size]; // expected-warning {{folded to constant}}
@@ -10,7 +10,7 @@ struct Chunk1 {
char data;
};
-int test1 = __builtin_offsetof(struct Chunk1, data);
+unsigned long test1 = __builtin_offsetof(struct Chunk1, data);
struct Chunk2 {
char padding[Size][Size][Size]; // expected-error {{array is too large}}
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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Thanks for the review. |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/162/builds/25751 Here is the relevant piece of the build log for the reference |
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When declaring multiple arrays of 1 ExaByte in a struct, the offset can exceed 2EB, causing incorrect struct size reporting (only 1EB). This fix ensures an error is thrown, preventing the generation of incorrect assembly. llvm#60272
rlavaee
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Jul 1, 2025
When declaring multiple arrays of 1 ExaByte in a struct, the offset can exceed 2EB, causing incorrect struct size reporting (only 1EB). This fix ensures an error is thrown, preventing the generation of incorrect assembly. llvm#60272
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When declaring multiple arrays of 1 ExaByte in a struct, the offset can exceed 2EB, causing incorrect struct size reporting (only 1EB). This fix ensures an error is thrown, preventing the generation of incorrect assembly. #60272