[LLDB] Consolidate C++ string buffer summaries #144258
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@llvm/pr-subscribers-lldb Author: nerix (Nerixyz) ChangesAs part of #143177, I moved the non-libc++ specific formatting of This PR picks that change, so the MSVC PR can be smaller. This resolves two FIXMEs in the libc++ tests, where empty u16 and u32 strings didn't have any prefix (u/U). Full diff: https://github.com/llvm/llvm-project/pull/144258.diff 5 Files Affected:
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp b/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp
index fc17b76804d9f..4e7569cd8a388 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp
@@ -116,15 +116,7 @@ bool lldb_private::formatters::WCharStringSummaryProvider(
return false;
// Get a wchar_t basic type from the current type system
- CompilerType wchar_compiler_type =
- valobj.GetCompilerType().GetBasicTypeFromAST(lldb::eBasicTypeWChar);
-
- if (!wchar_compiler_type)
- return false;
-
- // Safe to pass nullptr for exe_scope here.
- std::optional<uint64_t> size =
- llvm::expectedToOptional(wchar_compiler_type.GetBitSize(nullptr));
+ std::optional<uint64_t> size = GetWCharByteSize(*valobj.GetTargetSP());
if (!size)
return false;
const uint32_t wchar_size = *size;
@@ -136,13 +128,13 @@ bool lldb_private::formatters::WCharStringSummaryProvider(
options.SetPrefixToken("L");
switch (wchar_size) {
- case 8:
+ case 1:
return StringPrinter::ReadStringAndDumpToStream<StringElementType::UTF8>(
options);
- case 16:
+ case 2:
return StringPrinter::ReadStringAndDumpToStream<StringElementType::UTF16>(
options);
- case 32:
+ case 4:
return StringPrinter::ReadStringAndDumpToStream<StringElementType::UTF32>(
options);
default:
@@ -177,15 +169,7 @@ bool lldb_private::formatters::WCharSummaryProvider(
return false;
// Get a wchar_t basic type from the current type system
- CompilerType wchar_compiler_type =
- valobj.GetCompilerType().GetBasicTypeFromAST(lldb::eBasicTypeWChar);
-
- if (!wchar_compiler_type)
- return false;
-
- // Safe to pass nullptr for exe_scope here.
- std::optional<uint64_t> size =
- llvm::expectedToOptional(wchar_compiler_type.GetBitSize(nullptr));
+ std::optional<uint64_t> size = GetWCharByteSize(*valobj.GetTargetSP());
if (!size)
return false;
const uint32_t wchar_size = *size;
@@ -199,13 +183,13 @@ bool lldb_private::formatters::WCharSummaryProvider(
options.SetBinaryZeroIsTerminator(false);
switch (wchar_size) {
- case 8:
+ case 1:
return StringPrinter::ReadBufferAndDumpToStream<StringElementType::UTF8>(
options);
- case 16:
+ case 2:
return StringPrinter::ReadBufferAndDumpToStream<StringElementType::UTF16>(
options);
- case 32:
+ case 4:
return StringPrinter::ReadBufferAndDumpToStream<StringElementType::UTF32>(
options);
default:
@@ -214,3 +198,76 @@ bool lldb_private::formatters::WCharSummaryProvider(
}
return true;
}
+
+std::optional<uint64_t>
+lldb_private::formatters::GetWCharByteSize(Target &target) {
+ TypeSystemClangSP scratch_ts_sp =
+ ScratchTypeSystemClang::GetForTarget(target);
+ if (!scratch_ts_sp)
+ return {};
+
+ return llvm::expectedToOptional(
+ scratch_ts_sp->GetBasicType(lldb::eBasicTypeWChar).GetByteSize(nullptr));
+}
+
+template <StringPrinter::StringElementType element_type>
+bool lldb_private::formatters::StringBufferSummaryProvider(
+ Stream &stream, const TypeSummaryOptions &summary_options,
+ lldb::ValueObjectSP location_sp, uint64_t size, std::string prefix_token) {
+
+ if (size == 0) {
+ stream.PutCString(prefix_token);
+ stream.PutCString("\"\"");
+ return true;
+ }
+
+ if (!location_sp)
+ return false;
+
+ StringPrinter::ReadBufferAndDumpToStreamOptions options(*location_sp);
+
+ if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
+ const auto max_size =
+ location_sp->GetTargetSP()->GetMaximumSizeOfStringSummary();
+ if (size > max_size) {
+ size = max_size;
+ options.SetIsTruncated(true);
+ }
+ }
+
+ {
+ DataExtractor extractor;
+ const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
+ if (bytes_read < size)
+ return false;
+
+ options.SetData(std::move(extractor));
+ }
+ options.SetStream(&stream);
+ if (prefix_token.empty())
+ options.SetPrefixToken(nullptr);
+ else
+ options.SetPrefixToken(prefix_token);
+ options.SetQuote('"');
+ options.SetSourceSize(size);
+ options.SetBinaryZeroIsTerminator(false);
+ return StringPrinter::ReadBufferAndDumpToStream<element_type>(options);
+}
+
+// explicit instantiations for all string element types
+template bool
+lldb_private::formatters::StringBufferSummaryProvider<StringElementType::ASCII>(
+ Stream &, const TypeSummaryOptions &, lldb::ValueObjectSP, uint64_t,
+ std::string);
+template bool
+lldb_private::formatters::StringBufferSummaryProvider<StringElementType::UTF8>(
+ Stream &, const TypeSummaryOptions &, lldb::ValueObjectSP, uint64_t,
+ std::string);
+template bool
+lldb_private::formatters::StringBufferSummaryProvider<StringElementType::UTF16>(
+ Stream &, const TypeSummaryOptions &, lldb::ValueObjectSP, uint64_t,
+ std::string);
+template bool
+lldb_private::formatters::StringBufferSummaryProvider<StringElementType::UTF32>(
+ Stream &, const TypeSummaryOptions &, lldb::ValueObjectSP, uint64_t,
+ std::string);
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.h b/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.h
index a2b606d28cac1..b596950a28b18 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.h
+++ b/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.h
@@ -10,6 +10,7 @@
#ifndef LLDB_SOURCE_PLUGINS_LANGUAGE_CPLUSPLUS_CXXSTRINGTYPES_H
#define LLDB_SOURCE_PLUGINS_LANGUAGE_CPLUSPLUS_CXXSTRINGTYPES_H
+#include "lldb/DataFormatters/StringPrinter.h"
#include "lldb/DataFormatters/TypeSummary.h"
#include "lldb/Utility/Stream.h"
#include "lldb/ValueObject/ValueObject.h"
@@ -43,6 +44,17 @@ bool Char32SummaryProvider(ValueObject &valobj, Stream &stream,
bool WCharSummaryProvider(ValueObject &valobj, Stream &stream,
const TypeSummaryOptions &options); // wchar_t
+std::optional<uint64_t> GetWCharByteSize(Target &target);
+
+/// Print a summary for a string buffer to \a stream.
+///
+/// The buffer consists of a data pointer, \a location_sp, and a known \a size.
+template <StringPrinter::StringElementType element_type>
+bool StringBufferSummaryProvider(Stream &stream,
+ const TypeSummaryOptions &summary_options,
+ lldb::ValueObjectSP location_sp, uint64_t size,
+ std::string prefix_token);
+
} // namespace formatters
} // namespace lldb_private
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
index 358cf7d78fa21..4fe6626a3cf8a 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
@@ -24,6 +24,7 @@
#include "lldb/ValueObject/ValueObject.h"
#include "lldb/ValueObject/ValueObjectConstResult.h"
+#include "Plugins/Language/CPlusPlus/CxxStringTypes.h"
#include "Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h"
#include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
#include "lldb/lldb-enumerations.h"
@@ -535,70 +536,6 @@ ExtractLibcxxStringInfo(ValueObject &valobj) {
return std::make_pair(size, location_sp);
}
-static bool
-LibcxxWStringSummaryProvider(ValueObject &valobj, Stream &stream,
- const TypeSummaryOptions &summary_options,
- ValueObjectSP location_sp, size_t size) {
- if (size == 0) {
- stream.Printf("L\"\"");
- return true;
- }
- if (!location_sp)
- return false;
-
- StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
- if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
- const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
- if (size > max_size) {
- size = max_size;
- options.SetIsTruncated(true);
- }
- }
-
- DataExtractor extractor;
- const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
- if (bytes_read < size)
- return false;
-
- // std::wstring::size() is measured in 'characters', not bytes
- TypeSystemClangSP scratch_ts_sp =
- ScratchTypeSystemClang::GetForTarget(*valobj.GetTargetSP());
- if (!scratch_ts_sp)
- return false;
-
- auto wchar_t_size =
- scratch_ts_sp->GetBasicType(lldb::eBasicTypeWChar).GetByteSize(nullptr);
- if (!wchar_t_size)
- return false;
-
- options.SetData(std::move(extractor));
- options.SetStream(&stream);
- options.SetPrefixToken("L");
- options.SetQuote('"');
- options.SetSourceSize(size);
- options.SetBinaryZeroIsTerminator(false);
-
- switch (*wchar_t_size) {
- case 1:
- return StringPrinter::ReadBufferAndDumpToStream<
- lldb_private::formatters::StringPrinter::StringElementType::UTF8>(
- options);
- break;
-
- case 2:
- return StringPrinter::ReadBufferAndDumpToStream<
- lldb_private::formatters::StringPrinter::StringElementType::UTF16>(
- options);
- break;
-
- case 4:
- return StringPrinter::ReadBufferAndDumpToStream<
- lldb_private::formatters::StringPrinter::StringElementType::UTF32>(
- options);
- }
- return false;
-}
-
bool lldb_private::formatters::LibcxxWStringSummaryProvider(
ValueObject &valobj, Stream &stream,
const TypeSummaryOptions &summary_options) {
@@ -609,52 +546,22 @@ bool lldb_private::formatters::LibcxxWStringSummaryProvider(
ValueObjectSP location_sp;
std::tie(size, location_sp) = *string_info;
- return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
- location_sp, size);
-}
-
-template <StringPrinter::StringElementType element_type>
-static bool
-LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
- const TypeSummaryOptions &summary_options,
- std::string prefix_token, ValueObjectSP location_sp,
- uint64_t size) {
-
- if (size == 0) {
- stream.Printf("\"\"");
- return true;
- }
-
- if (!location_sp)
+ auto wchar_t_size = GetWCharByteSize(*valobj.GetTargetSP());
+ if (!wchar_t_size)
return false;
- StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
-
- if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
- const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
- if (size > max_size) {
- size = max_size;
- options.SetIsTruncated(true);
- }
- }
-
- {
- DataExtractor extractor;
- const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
- if (bytes_read < size)
- return false;
-
- options.SetData(std::move(extractor));
+ switch (*wchar_t_size) {
+ case 1:
+ return StringBufferSummaryProvider<StringPrinter::StringElementType::UTF8>(
+ stream, summary_options, location_sp, size, "L");
+ case 2:
+ return StringBufferSummaryProvider<StringPrinter::StringElementType::UTF16>(
+ stream, summary_options, location_sp, size, "L");
+ case 4:
+ return StringBufferSummaryProvider<StringPrinter::StringElementType::UTF32>(
+ stream, summary_options, location_sp, size, "L");
}
- options.SetStream(&stream);
- if (prefix_token.empty())
- options.SetPrefixToken(nullptr);
- else
- options.SetPrefixToken(prefix_token);
- options.SetQuote('"');
- options.SetSourceSize(size);
- options.SetBinaryZeroIsTerminator(false);
- return StringPrinter::ReadBufferAndDumpToStream<element_type>(options);
+ return false;
}
template <StringPrinter::StringElementType element_type>
@@ -669,8 +576,8 @@ LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
ValueObjectSP location_sp;
std::tie(size, location_sp) = *string_info;
- return LibcxxStringSummaryProvider<element_type>(
- valobj, stream, summary_options, prefix_token, location_sp, size);
+ return StringBufferSummaryProvider<element_type>(
+ stream, summary_options, location_sp, size, prefix_token);
}
template <StringPrinter::StringElementType element_type>
static bool formatStringImpl(ValueObject &valobj, Stream &stream,
@@ -742,8 +649,8 @@ static bool formatStringViewImpl(ValueObject &valobj, Stream &stream,
return true;
}
- return LibcxxStringSummaryProvider<element_type>(
- valobj, stream, summary_options, prefix_token, dataobj, size);
+ return StringBufferSummaryProvider<element_type>(stream, summary_options,
+ dataobj, size, prefix_token);
}
bool lldb_private::formatters::LibcxxStringViewSummaryProviderASCII(
@@ -781,8 +688,22 @@ bool lldb_private::formatters::LibcxxWStringViewSummaryProvider(
return true;
}
- return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
- dataobj, size);
+ auto wchar_t_size = GetWCharByteSize(*valobj.GetTargetSP());
+ if (!wchar_t_size)
+ return false;
+
+ switch (*wchar_t_size) {
+ case 1:
+ return StringBufferSummaryProvider<StringPrinter::StringElementType::UTF8>(
+ stream, summary_options, dataobj, size, "L");
+ case 2:
+ return StringBufferSummaryProvider<StringPrinter::StringElementType::UTF16>(
+ stream, summary_options, dataobj, size, "L");
+ case 4:
+ return StringBufferSummaryProvider<StringPrinter::StringElementType::UTF32>(
+ stream, summary_options, dataobj, size, "L");
+ }
+ return false;
}
static bool
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string/TestDataFormatterLibcxxString.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string/TestDataFormatterLibcxxString.py
index 5c5cf4ca16b98..32764629d65a7 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string/TestDataFormatterLibcxxString.py
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string/TestDataFormatterLibcxxString.py
@@ -65,11 +65,9 @@ def cleanup():
'(%s::wstring) IHaveEmbeddedZerosToo = L"hello world!\\0てざ ル゜䋨ミ㠧槊 きゅへ狦穤襩 じゃ馩リョ 䤦監"'
% ns,
'(%s::u16string) u16_string = u"ß水氶"' % ns,
- # FIXME: This should have a 'u' prefix.
- '(%s::u16string) u16_empty = ""' % ns,
+ '(%s::u16string) u16_empty = u""' % ns,
'(%s::u32string) u32_string = U"🍄🍅🍆🍌"' % ns,
- # FIXME: This should have a 'U' prefix.
- '(%s::u32string) u32_empty = ""' % ns,
+ '(%s::u32string) u32_empty = U""' % ns,
"(%s::string *) null_str = nullptr" % ns,
],
)
@@ -123,7 +121,7 @@ def cleanup():
% ns,
'(%s::u16string) u16_string = u"ß水氶"' % ns,
'(%s::u32string) u32_string = U"🍄🍅🍆🍌"' % ns,
- '(%s::u32string) u32_empty = ""' % ns,
+ '(%s::u32string) u32_empty = U""' % ns,
"(%s::string *) null_str = nullptr" % ns,
],
)
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string_view/TestDataFormatterLibcxxStringView.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string_view/TestDataFormatterLibcxxStringView.py
index f8fc8ae66405b..3883395f23924 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string_view/TestDataFormatterLibcxxStringView.py
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/string_view/TestDataFormatterLibcxxStringView.py
@@ -81,11 +81,11 @@ def cleanup():
summary='L"hello world!\\0てざ ル゜䋨ミ㠧槊 きゅへ狦穤襩 じゃ馩リョ 䤦監"',
)
self.expect_var_path("u16_string", type="std::u16string_view", summary='u"ß水氶"')
- self.expect_var_path("u16_empty", type="std::u16string_view", summary='""')
+ self.expect_var_path("u16_empty", type="std::u16string_view", summary='u""')
self.expect_var_path(
"u32_string", type="std::u32string_view", summary='U"🍄🍅🍆🍌"'
)
- self.expect_var_path("u32_empty", type="std::u32string_view", summary='""')
+ self.expect_var_path("u32_empty", type="std::u32string_view", summary='U""')
self.expect_var_path(
"oops", type="std::string_view", summary='"Hellooo World\\n"'
)
@@ -145,11 +145,11 @@ def cleanup():
summary='L"hello world!\\0てざ ル゜䋨ミ㠧槊 きゅへ狦穤襩 じゃ馩リョ 䤦監"',
)
self.expect_var_path("u16_string", type="std::u16string_view", summary='u"ß水氶"')
- self.expect_var_path("u16_empty", type="std::u16string_view", summary='""')
+ self.expect_var_path("u16_empty", type="std::u16string_view", summary='u""')
self.expect_var_path(
"u32_string", type="std::u32string_view", summary='U"🍄🍅🍆🍌"'
)
- self.expect_var_path("u32_empty", type="std::u32string_view", summary='""')
+ self.expect_var_path("u32_empty", type="std::u32string_view", summary='U""')
self.runCmd("cont")
self.expect(
|
Michael137
reviewed
Jun 16, 2025
| @@ -199,13 +183,13 @@ bool lldb_private::formatters::WCharSummaryProvider( | |||
| options.SetBinaryZeroIsTerminator(false); | |||
|
|
|||
| switch (wchar_size) { | |||
| case 8: | |||
| case 1: | |||
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Hmm so this switch was always wrong in the past? Is this why the test changes had to be made?
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No, this wasn't wrong. It used the bit size before, and the libc++ summary used the byte size. I'm not sure which is better (I suppose 8 bits/byte is true for all targets supported by LLDB).
This reminds me of another difference: The *CharSummaryProviders used valobj.GetCompilerType().GetBasicTypeFromAST() and the libc++ formatters used ScratchTypeSystemClang::GetBasicType(). Is there a big difference between them, and is one preferred over the other?
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No, this wasn't wrong. It used the bit size before, and the libc++ summary used the byte size. I'm not sure which is better (I suppose 8 bits/byte is true for all targets supported by LLDB).
Ah I see. Making them consistent makes sense
The *CharSummaryProviders used valobj.GetCompilerType().GetBasicTypeFromAST() and the libc++ formatters used ScratchTypeSystemClang::GetBasicType(). Is there a big difference between them, and is one preferred over the other?
The ScratchTypeSystemClang is the AST that is shared between all expressions run in the target. Whereas the TypeSystem underlying a CompilerType only contains the AST nodes created when the ValueObject and its type were created. It shouldn't make a difference for primitive types. And especially shouldn't make a difference when all we need to do is get the bytesize. That being said, I'd prefer using valobj.GetCompilerType().GetBasicTypeFromAST() (assuming that doesn't break anything). Reaching into the scratch typesystem feels weird here
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I refactored it to use valobj.GetCompilerType().GetBasicTypeFromAST() now.
Michael137
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Jun 16, 2025
Michael137
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| Stream &stream, const TypeSummaryOptions &summary_options, | ||
| lldb::ValueObjectSP location_sp, uint64_t size, std::string prefix_token) { | ||
|
|
||
| if (size == 0) { |
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Ah i see, this is where the tests get fixed
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| /// A pointer to a string buffer. It doesn't need to be null-terminated. | ||
| /// The size is given by \a size. |
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I find location_sp to be quite a confusing name for this. You didn't come up with the name so I won't make you change this parameter. (could do it in a separate change)
But could we reword the explanation to something like:
Suggested change
| /// A pointer to a string buffer. It doesn't need to be null-terminated. | |
| /// The size is given by \a size. | |
| /// ValueObject of a pointer to the string being printed. |
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|
Do you need me to merge this? |
Oh yea, that would be great! |
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As part of llvm#143177, I moved the non-libc++ specific formatting of `std::string`s out to `CxxStringTypes` as MSVC's STL `std::string` can also be thought of a pointer+size pair. I named this kind of string "string buffer". This PR picks that change, so the MSVC PR can be smaller. Unfortunately, libstdc++'s `std::string` does not fit this (it also uses a different string printer function). This resolves two FIXMEs in the libc++ tests, where empty u16 and u32 strings didn't have any prefix (u/U).
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As part of #143177, I moved the non-libc++ specific formatting of
std::strings out toCxxStringTypesas MSVC's STLstd::stringcan also be thought of a pointer+size pair. I named this kind of string "string buffer".This PR picks that change, so the MSVC PR can be smaller.
Unfortunately, libstdc++'s
std::stringdoes not fit this (it also uses a different string printer function).This resolves two FIXMEs in the libc++ tests, where empty u16 and u32 strings didn't have any prefix (u/U).