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[lldb][TypeSystemClang] Create VLAs of explicitly 0-size as ConstantA…
…rrayType (#100710) Depends on #100674 Currently, we treat VLAs declared as `int[]` and `int[0]` identically. I.e., we create them as `IncompleteArrayType`s. However, the `DW_AT_count` for `int[0]` *does* exist, and is retrievable without an execution context. This patch decouples the notion of "has 0 elements" from "has no known `DW_AT_count`". This aligns with how Clang represents `int[0]` in the AST (it treats it as a `ConstantArrayType` of 0 size). This issue was surfaced when adapting LLDB to #93069. There, the `__compressed_pair_padding` type has a `char[0]` member. If we previously got the `__compressed_pair_padding` out of a module (where clang represents `char[0]` as a `ConstantArrayType`), and try to merge the AST with one we got from DWARF (where LLDB used to represent `char[0]` as an `IncompleteArrayType`), the AST structural equivalence check fails, resulting in silent ASTImporter failures. This manifested in a failure in `TestNonModuleTypeSeparation.py`. **Implementation** 1. Adjust `ParseChildArrayInfo` to store the element counts of each VLA dimension as an `optional<uint64_t>`, instead of a regular `uint64_t`. So when we pass this down to `CreateArrayType`, we have a better heuristic for what is an `IncompleteArrayType`. 2. In `TypeSystemClang::GetBitSize`, if we encounter a `ConstantArrayType` simply return the size that it was created with. If we couldn't determine the authoritative bound from DWARF during parsing, we would've created an `IncompleteArrayType`. This ensures that `GetBitSize` on arrays with `DW_AT_count 0x0` returns `0` (whereas previously it would've returned a `std::nullopt`, causing that `FieldDecl` to just get dropped during printing)
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| Original file line number | Diff line number | Diff line change |
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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 | ||
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| struct Foo { | ||
| static constexpr int n = 1; | ||
| int m_vlaN[n]; | ||
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| int m_vla0[0]; | ||
| }; | ||
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| int main() { | ||
| Foo f; | ||
| f.m_vlaN[0] = 60; | ||
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| // 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: } | ||
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| int vla0[0] = {}; | ||
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| // CHECK: (lldb) frame var vla0 | ||
| // CHECK-NEXT: (int[0]) vla0 = {} | ||
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| int fla0[] = {}; | ||
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| // CHECK: (lldb) frame var fla0 | ||
| // CHECK-NEXT: (int[0]) fla0 = {} | ||
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| int fla1[] = {42}; | ||
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| // CHECK: (lldb) frame var fla1 | ||
| // CHECK-NEXT: (int[1]) fla1 = ([0] = 42) | ||
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| int vla01[0][1]; | ||
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| // CHECK: (lldb) frame var vla01 | ||
| // CHECK-NEXT: (int[0][1]) vla01 = {} | ||
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| int vla10[1][0]; | ||
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| // CHECK: (lldb) frame var vla10 | ||
| // CHECK-NEXT: (int[1][0]) vla10 = ([0] = int[0] | ||
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| int n = 3; | ||
| int vlaN[n]; | ||
| for (int i = 0; i < n; ++i) | ||
| vlaN[i] = -i; | ||
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| // CHECK: (lldb) frame var vlaN | ||
| // CHECK-NEXT: (int[]) vlaN = ([0] = 0, [1] = -1, [2] = -2) | ||
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| 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; | ||
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| // 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: } | ||
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| __builtin_debugtrap(); | ||
| } |