[Lldb-commits] [lldb] [lldb] add libstdcpp span formatter (PR #168705)
Ebuka Ezike via lldb-commits
lldb-commits at lists.llvm.org
Wed Nov 19 05:29:51 PST 2025
https://github.com/da-viper created https://github.com/llvm/llvm-project/pull/168705
None
>From 24cf7b3359beba96c5079d406ebc124e17bb0288 Mon Sep 17 00:00:00 2001
From: Ebuka Ezike <yerimyah1 at gmail.com>
Date: Tue, 18 Nov 2025 19:35:00 +0000
Subject: [PATCH] [lldb] add libstdcpp span formatter
---
.../Plugins/Language/CPlusPlus/CMakeLists.txt | 1 +
.../Language/CPlusPlus/CPlusPlusLanguage.cpp | 9 ++
.../Plugins/Language/CPlusPlus/LibStdcpp.h | 4 +
.../Language/CPlusPlus/LibStdcppSpan.cpp | 112 ++++++++++++++++++
.../generic/span/TestDataFormatterStdSpan.py | 26 ++--
5 files changed, 145 insertions(+), 7 deletions(-)
create mode 100644 lldb/source/Plugins/Language/CPlusPlus/LibStdcppSpan.cpp
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt b/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
index ca4fd3f680484..c52d3bdb31284 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
+++ b/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
@@ -31,6 +31,7 @@ add_lldb_library(lldbPluginCPlusPlusLanguage PLUGIN
LibCxxValarray.cpp
LibCxxVector.cpp
LibStdcpp.cpp
+ LibStdcppSpan.cpp
LibStdcppTuple.cpp
LibStdcppUniquePointer.cpp
MsvcStl.cpp
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index 3cbae1e87f3dc..597cf1e06ffe2 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -1411,6 +1411,10 @@ static void LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
stl_synth_flags,
"lldb.formatters.cpp.gnu_libstdcpp.StdForwardListSynthProvider")));
+ AddCXXSynthetic(cpp_category_sp, LibStdcppSpanSyntheticFrontEndCreator,
+ "libstdc++ std::span synthetic children", "^std::span<.+>$",
+ stl_deref_flags, true);
+
stl_summary_flags.SetDontShowChildren(false);
stl_summary_flags.SetSkipPointers(false);
@@ -1501,6 +1505,11 @@ static void LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
lldb_private::formatters::StdlibCoroutineHandleSummaryProvider,
"libstdc++ std::coroutine_handle summary provider",
libstdcpp_std_coroutine_handle_regex, stl_summary_flags, true);
+
+ AddCXXSummary(cpp_category_sp,
+ lldb_private::formatters::ContainerSizeSummaryProvider,
+ "libstdc++ std::span summary provider", "^std::span<.+>$",
+ stl_summary_flags, true);
}
static lldb_private::SyntheticChildrenFrontEnd *
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.h b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.h
index 429142f63a4bd..8d2c81f2bbcbb 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.h
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.h
@@ -37,6 +37,10 @@ SyntheticChildrenFrontEnd *
LibstdcppMapIteratorSyntheticFrontEndCreator(CXXSyntheticChildren *,
lldb::ValueObjectSP);
+SyntheticChildrenFrontEnd *
+LibStdcppSpanSyntheticFrontEndCreator(CXXSyntheticChildren *,
+ lldb::ValueObjectSP);
+
SyntheticChildrenFrontEnd *
LibStdcppTupleSyntheticFrontEndCreator(CXXSyntheticChildren *,
lldb::ValueObjectSP);
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcppSpan.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibStdcppSpan.cpp
new file mode 100644
index 0000000000000..98ea769c78a77
--- /dev/null
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibStdcppSpan.cpp
@@ -0,0 +1,112 @@
+//===---------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "LibStdcpp.h"
+
+#include "lldb/DataFormatters/FormattersHelpers.h"
+#include "lldb/Utility/ConstString.h"
+#include "lldb/ValueObject/ValueObject.h"
+#include "llvm/ADT/APSInt.h"
+#include "llvm/Support/Error.h"
+#include <cstddef>
+#include <optional>
+
+using namespace lldb;
+
+namespace lldb_private::formatters {
+
+class LibStdcppSpanSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+ LibStdcppSpanSyntheticFrontEnd(const lldb::ValueObjectSP &valobj_sp)
+ : SyntheticChildrenFrontEnd(*valobj_sp) {
+ if (valobj_sp)
+ Update();
+ }
+
+ ~LibStdcppSpanSyntheticFrontEnd() override = default;
+
+ llvm::Expected<uint32_t> CalculateNumChildren() override {
+ return m_num_elements;
+ }
+
+ lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override {
+ if (!m_start)
+ return {};
+
+ uint64_t offset = (static_cast<uint64_t>(idx) * m_element_size);
+ offset += m_start->GetValueAsUnsigned(0);
+ const std::string name = llvm::formatv("[{0}]", idx);
+ return CreateValueObjectFromAddress(
+ name, offset, m_backend.GetExecutionContextRef(), m_element_type);
+ }
+
+ lldb::ChildCacheState Update() override {
+ const ValueObjectSP element_ptr =
+ m_backend.GetChildMemberWithName(ConstString("_M_ptr"));
+ if (!element_ptr)
+ return lldb::ChildCacheState::eRefetch;
+
+ m_element_type = element_ptr->GetCompilerType().GetPointeeType();
+
+ // Get element size.
+ llvm::Expected<uint64_t> size_or_err = m_element_type.GetByteSize(nullptr);
+ if (!size_or_err) {
+ LLDB_LOG_ERRORV(GetLog(LLDBLog::DataFormatters), size_or_err.takeError(),
+ "{0}");
+ return lldb::ChildCacheState::eReuse;
+ }
+
+ m_element_size = *size_or_err;
+ if (m_element_size > 0) {
+ m_start = element_ptr.get();
+ }
+
+ // Get number of elements.
+ if (auto size_sp = m_backend.GetChildAtNamePath(
+ {ConstString("_M_extent"), ConstString("_M_extent_value")})) {
+ m_num_elements = size_sp->GetValueAsUnsigned(0);
+ } else if (auto arg =
+ m_backend.GetCompilerType().GetIntegralTemplateArgument(1)) {
+
+ m_num_elements = arg->value.GetAPSInt().getLimitedValue();
+ }
+
+ return lldb::ChildCacheState::eReuse;
+ }
+
+ llvm::Expected<size_t> GetIndexOfChildWithName(ConstString name) override {
+ if (!m_start)
+ return llvm::createStringError("Type has no child named '%s'",
+ name.AsCString());
+ auto optional_idx = formatters::ExtractIndexFromString(name.GetCString());
+ if (!optional_idx) {
+ return llvm::createStringError("Type has no child named '%s'",
+ name.AsCString());
+ }
+ return *optional_idx;
+ }
+
+private:
+ ValueObject *m_start = nullptr; /// First element of span. Held, not owned.
+ CompilerType m_element_type; /// Type of span elements.
+ size_t m_num_elements = 0; /// Number of elements in span.
+ uint32_t m_element_size = 0; /// Size in bytes of each span element.
+};
+
+SyntheticChildrenFrontEnd *
+LibStdcppSpanSyntheticFrontEndCreator(CXXSyntheticChildren * /*unused*/,
+ lldb::ValueObjectSP valobj_sp) {
+ if (!valobj_sp)
+ return nullptr;
+ const CompilerType type = valobj_sp->GetCompilerType();
+ if (!type || type.GetNumTemplateArguments() != 2)
+ return nullptr;
+ return new LibStdcppSpanSyntheticFrontEnd(valobj_sp);
+}
+
+} // namespace lldb_private::formatters
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/span/TestDataFormatterStdSpan.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/span/TestDataFormatterStdSpan.py
index a45c0ff551323..f586fb3d698c1 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/span/TestDataFormatterStdSpan.py
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/span/TestDataFormatterStdSpan.py
@@ -74,7 +74,7 @@ def do_test(self):
result_summary="item 0 is 1",
)
- self.runCmd("type summary delete span")
+ self.runCmd("type summary clear")
# New span with strings
lldbutil.continue_to_breakpoint(process, bkpt)
@@ -155,12 +155,6 @@ def do_test(self):
)
self.check_size("nested", 2)
- @skipIf(compiler="clang", compiler_version=["<", "11.0"])
- @add_test_categories(["libc++"])
- def test_libcxx(self):
- self.build(dictionary={"USE_LIBCPP": 1})
- self.do_test()
-
def do_test_ref_and_ptr(self):
"""Test that std::span is correctly formatted when passed by ref and ptr"""
(self.target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
@@ -174,8 +168,26 @@ def do_test_ref_and_ptr(self):
self.expect("frame variable ptr", patterns=["ptr = 0x[0-9a-f]+ size=5"])
+ @skipIf(compiler="clang", compiler_version=["<", "11.0"])
+ @add_test_categories(["libc++"])
+ def test_libcxx(self):
+ self.build(dictionary={"USE_LIBCPP": 1})
+ self.do_test()
+
@skipIf(compiler="clang", compiler_version=["<", "11.0"])
@add_test_categories(["libc++"])
def test_ref_and_ptr_libcxx(self):
self.build(dictionary={"USE_LIBCPP": 1})
self.do_test_ref_and_ptr()
+
+ @skipIf(compiler="clang", compiler_version=["<", "11.0"])
+ @add_test_categories(["libstdcxx"])
+ def test_libstdcxx(self):
+ self.build(dictionary={"USE_LIBSTDCPP": 1})
+ self.do_test()
+
+ @skipIf(compiler="clang", compiler_version=["<", "11.0"])
+ @add_test_categories(["libstdcxx"])
+ def test_ref_and_ptr_libstdcxx(self):
+ self.build(dictionary={"USE_LIBSTDCPP": 1})
+ self.do_test_ref_and_ptr()
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