[Lldb-commits] [PATCH] D127481: [LLDB][formatters] Add formatter for libc++'s std::span

[Michael Buch via Phabricator via lldb-commits]

Michael137 created this revision.
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This patch adds a libcxx formatter for std::span. The
implementation is based on the libcxx formatter for
std::vector. The main difference is the fact that
std::span conditionally has a __size member based
on whether it has a static or dynamic extent.

Example output of formatted span:

  (std::span<const int, 18446744073709551615>) $0 = size=6 {
    [0] = 0
    [1] = 1
    [2] = 2
    [3] = 3
    [4] = 4
    [5] = 5
  }

The second template parameter here is actually `std::dynamic_extent`,
but the type declaration we get back from the `TypeSystemClang` is the
actual value (which in this case is `(size_t)-1`). This is consistent
with diagnostics from clang, which doesn't desugar this value either.
E.g.,:

  span.cpp:30:31: error: implicit instantiation of undefined template
      'Undefined<std::span<int, 18446744073709551615>>'

Testing:

- Added API-tests
- Confirmed manually using LLDB cli that printing spans works in various scenarios


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D127481

Files:
  lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
  lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
  lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
  lldb/source/Plugins/Language/CPlusPlus/LibCxxSpan.cpp
  lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/span/Makefile
  lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/span/TestDataFormatterLibcxxSpan.py
  lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/span/main.cpp

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