[Lldb-commits] [lldb] ed95844 - [lldb][test] Add tests for alignof on class with overlapping bases (#97068)

[via lldb-commits]

Author: Michael Buch
Date: 2024-06-29T08:38:17+01:00
New Revision: ed9584457def4a51596b9d72ce76a1bfed88fa30

URL: https://github.com/llvm/llvm-project/commit/ed9584457def4a51596b9d72ce76a1bfed88fa30
DIFF: https://github.com/llvm/llvm-project/commit/ed9584457def4a51596b9d72ce76a1bfed88fa30.diff

LOG: [lldb][test] Add tests for alignof on class with overlapping bases (#97068)

Follow-up to https://github.com/llvm/llvm-project/pull/96932

Adds XFAILed test where LLDB incorrectly infers the alignment of a
derived class whose bases are overlapping due to [[no_unique_address]].
Specifically, the `InferAlignment` code-path of the
`ItaniumRecordLayoutBuilder` assumes that overlapping base offsets imply
a packed structure and thus sets alignment to 1. See discussion in
https://github.com/llvm/llvm-project/pull/93809.

Also adds test where LLDB correctly infers an alignment of `1` when a
packed base class is overlapping with other bases.

Lastly, there were a couple of `alignof` inconsistencies which I
encapsulated in an XFAIL-ed `packed-alignof.cpp`.

Added: 
    lldb/test/Shell/SymbolFile/DWARF/no_unique_address-base-alignment.cpp
    lldb/test/Shell/SymbolFile/DWARF/packed-alignof.cpp

Modified: 
    lldb/test/Shell/SymbolFile/DWARF/packed.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/test/Shell/SymbolFile/DWARF/no_unique_address-base-alignment.cpp b/lldb/test/Shell/SymbolFile/DWARF/no_unique_address-base-alignment.cpp
new file mode 100644
index 0000000000000..15d8de0e3ee98
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/no_unique_address-base-alignment.cpp
@@ -0,0 +1,30 @@
+// XFAIL: *
+
+// RUN: %clangxx_host -gdwarf -o %t %s
+// RUN: %lldb %t \
+// RUN:   -o "expr alignof(OverlappingDerived)" \
+// RUN:   -o "expr sizeof(OverlappingDerived)" \
+// RUN:   -o exit | FileCheck %s
+
+struct Empty {};
+
+struct OverlappingBase {
+  [[no_unique_address]] Empty e;
+};
+static_assert(sizeof(OverlappingBase) == 1);
+static_assert(alignof(OverlappingBase) == 1);
+
+struct Base {
+  int mem;
+};
+
+struct OverlappingDerived : Base, OverlappingBase {};
+static_assert(alignof(OverlappingDerived) == 4);
+static_assert(sizeof(OverlappingDerived) == 4);
+
+// CHECK:      (lldb) expr alignof(OverlappingDerived)
+// CHECK-NEXT: ${{.*}} = 4
+// CHECK:      (lldb) expr sizeof(OverlappingDerived)
+// CHECK-NEXT: ${{.*}} = 4
+
+int main() { OverlappingDerived d; }

diff  --git a/lldb/test/Shell/SymbolFile/DWARF/packed-alignof.cpp b/lldb/test/Shell/SymbolFile/DWARF/packed-alignof.cpp
new file mode 100644
index 0000000000000..dcc02736a9be7
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/packed-alignof.cpp
@@ -0,0 +1,43 @@
+// XFAIL: *
+//
+// RUN: %clangxx_host -gdwarf -o %t %s
+// RUN: %lldb %t \
+// RUN:   -o "expr alignof(base)" \
+// RUN:   -o "expr alignof(packed_base)" \
+// RUN:   -o "expr alignof(derived)" \
+// RUN:   -o "expr sizeof(derived)" \
+// RUN:   -o exit | FileCheck %s
+
+struct __attribute__((packed)) packed {
+  int x;
+  char y;
+  int z;
+} g_packed_struct;
+
+// LLDB incorrectly calculates alignof(base)
+struct foo {};
+struct base : foo { int x; };
+static_assert(alignof(base) == 4);
+
+// CHECK:      (lldb) expr alignof(base)
+// CHECK-NEXT: ${{.*}} = 4
+
+// LLDB incorrectly calculates alignof(packed_base)
+struct __attribute__((packed)) packed_base { int x; };
+static_assert(alignof(packed_base) == 1);
+
+// CHECK:      (lldb) expr alignof(packed_base)
+// CHECK-NEXT: ${{.*}} = 1
+
+struct derived : packed, packed_base {
+  short s;
+} g_derived;
+static_assert(alignof(derived) == 2);
+static_assert(sizeof(derived) == 16);
+
+// CHECK:      (lldb) expr alignof(derived)
+// CHECK-NEXT: ${{.*}} = 2
+// CHECK:      (lldb) expr sizeof(derived)
+// CHECK-NEXT: ${{.*}} = 16
+
+int main() {}

diff  --git a/lldb/test/Shell/SymbolFile/DWARF/packed.cpp b/lldb/test/Shell/SymbolFile/DWARF/packed.cpp
index 640a2e0454c92..360293b1d4184 100644
--- a/lldb/test/Shell/SymbolFile/DWARF/packed.cpp
+++ b/lldb/test/Shell/SymbolFile/DWARF/packed.cpp
@@ -4,18 +4,10 @@
 // RUN:   -o "expr sizeof(packed)" \
 // RUN:   -o "expr alignof(packed_and_aligned)" \
 // RUN:   -o "expr sizeof(packed_and_aligned)" \
+// RUN:   -o "expr alignof(derived)" \
+// RUN:   -o "expr sizeof(derived)" \
 // RUN:   -o exit | FileCheck %s
 
-// CHECK:      (lldb) expr alignof(packed)
-// CHECK-NEXT: ${{.*}} = 1
-// CHECK:      (lldb) expr sizeof(packed)
-// CHECK-NEXT: ${{.*}} = 9
-
-// CHECK:      (lldb) expr alignof(packed_and_aligned)
-// CHECK-NEXT: ${{.*}} = 16
-// CHECK:      (lldb) expr sizeof(packed_and_aligned)
-// CHECK-NEXT: ${{.*}} = 16
-
 struct __attribute__((packed)) packed {
   int x;
   char y;
@@ -24,6 +16,11 @@ struct __attribute__((packed)) packed {
 static_assert(alignof(packed) == 1);
 static_assert(sizeof(packed) == 9);
 
+// CHECK:      (lldb) expr alignof(packed)
+// CHECK-NEXT: ${{.*}} = 1
+// CHECK:      (lldb) expr sizeof(packed)
+// CHECK-NEXT: ${{.*}} = 9
+
 struct __attribute__((packed, aligned(16))) packed_and_aligned {
   int x;
   char y;
@@ -32,4 +29,21 @@ struct __attribute__((packed, aligned(16))) packed_and_aligned {
 static_assert(alignof(packed_and_aligned) == 16);
 static_assert(sizeof(packed_and_aligned) == 16);
 
+// CHECK:      (lldb) expr alignof(packed_and_aligned)
+// CHECK-NEXT: ${{.*}} = 16
+// CHECK:      (lldb) expr sizeof(packed_and_aligned)
+// CHECK-NEXT: ${{.*}} = 16
+
+struct __attribute__((packed)) packed_base { int x; };
+static_assert(alignof(packed_base) == 1);
+
+struct derived : packed, packed_base {} g_derived;
+static_assert(alignof(derived) == 1);
+static_assert(sizeof(derived) == 13);
+
+// CHECK:      (lldb) expr alignof(derived)
+// CHECK-NEXT: ${{.*}} = 1
+// CHECK:      (lldb) expr sizeof(derived)
+// CHECK-NEXT: ${{.*}} = 13
+
 int main() {}