[Lldb-commits] [lldb] [lldb][TypeSystemClang] Create VLAs of explicitly 0-size as ConstantArrayType (PR #100710)

[Michael Buch via lldb-commits]

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@@ -0,0 +1,80 @@
+// RUN: %clangxx_host -gdwarf -std=c++11 -o %t %s
+// RUN: %lldb %t \
+// RUN:   -o run \
+// RUN:   -o "frame var --show-types f" \
+// RUN:   -o "frame var vla0" \
+// RUN:   -o "frame var fla0" \
+// RUN:   -o "frame var fla1" \
+// RUN:   -o "frame var vla01" \
+// RUN:   -o "frame var vla10" \
+// RUN:   -o "frame var vlaN" \
+// RUN:   -o "frame var vlaNM" \
+// RUN:   -o exit | FileCheck %s
+
+struct Foo {
+  static constexpr int n = 1;
+  int m_vlaN[n];
+
+  int m_vla0[0];
+};
+
+int main() {
+  Foo f;
+  f.m_vlaN[0] = 60;
+
+  // CHECK:      (lldb) frame var --show-types f
+  // CHECK-NEXT: (Foo) f = {
+  // CHECK-NEXT:   (int[1]) m_vlaN = {
+  // CHECK-NEXT:     (int) [0] = 60
+  // CHECK-NEXT:   }
+  // CHECK-NEXT:   (int[0]) m_vla0 = {}
+  // CHECK-NEXT: }
+
+  int vla0[0] = {};
+
+  // CHECK:      (lldb) frame var vla0
+  // CHECK-NEXT: (int[0]) vla0 = {}
+
+  int fla0[] = {};
+
+  // CHECK:      (lldb) frame var fla0
+  // CHECK-NEXT: (int[0]) fla0 = {}
+
+  int fla1[] = {42};
+
+  // CHECK:      (lldb) frame var fla1
+  // CHECK-NEXT: (int[1]) fla1 = ([0] = 42)
+
+  int vla01[0][1];
+
+  // CHECK:      (lldb) frame var vla01
+  // CHECK-NEXT: (int[0][1]) vla01 = {}
+
+  int vla10[1][0];
+
+  // CHECK:      (lldb) frame var vla10
+  // CHECK-NEXT: (int[1][0]) vla10 = ([0] = int[0]
+
+  int n = 3;
+  int vlaN[n];
+  for (int i = 0; i < n; ++i)
+    vlaN[i] = -i;
+
+  // CHECK:      (lldb) frame var vlaN
+  // CHECK-NEXT: (int[]) vlaN = ([0] = 0, [1] = -1, [2] = -2)
+
+  int m = 2;
+  int vlaNM[n][m];
+  for (int i = 0; i < n; ++i)
+    for (int j = 0; j < m; ++j)
+      vlaNM[i][j] = i + j;
+
+  // FIXME: multi-dimensional VLAs aren't well supported
+  // CHECK:      (lldb) frame var vlaNM
+  // CHECK-NEXT: (int[][]) vlaNM = {
+  // CHECK-NEXT:   [0] = ([0] = 0, [1] = 1, [2] = 1)
+  // CHECK-NEXT:   [1] = ([0] = 1, [1] = 1, [2] = 2)
+  // CHECK-NEXT: }
----------------
Michael137 wrote:

This is also broken without this patch. E.g., accessing elements of a VLA with non-constant bounds will return garbage. My hunch is that we just calculate the stride incorrectly (or something related to calculating children count).

https://github.com/llvm/llvm-project/pull/100710