[lldb][DataFormatter] Allow std::string formatters to match against custom allocators (llvm#156050)

Michael137 · tru · commit fa462a66e418 · 2025-09-08T09:42:05.000+02:00
This came up in llvm#155691. For `std::basic_string` our formatter matching logic required the allocator template parameter to be a `std::allocator`. There is no compelling reason (that I know of) why this would be required for us to apply the existing formatter to the string. We don't check the `allocator` parameter for other STL containers either. This meant that `std::string` that used custom allocators wouldn't be formatted. This patch relaxes the regex for `basic_string`. (cherry picked from commit 4b362f1)
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -790,31 +790,27 @@ static void LoadLibCxxFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
                 lldb_private::formatters::LibcxxStringSummaryProviderASCII,
                 "std::string summary provider",
                 "^std::__[[:alnum:]]+::basic_string<char, "
-                "std::__[[:alnum:]]+::char_traits<char>, "
-                "std::__[[:alnum:]]+::allocator<char> >$",
+                "std::__[[:alnum:]]+::char_traits<char>,.*>$",
                 stl_summary_flags, true);
   AddCXXSummary(cpp_category_sp,
                 lldb_private::formatters::LibcxxStringSummaryProviderASCII,
                 "std::string summary provider",
                 "^std::__[[:alnum:]]+::basic_string<unsigned char, "
-                "std::__[[:alnum:]]+::char_traits<unsigned char>, "
-                "std::__[[:alnum:]]+::allocator<unsigned char> >$",
+                "std::__[[:alnum:]]+::char_traits<unsigned char>,.*>$",
                 stl_summary_flags, true);
 
   AddCXXSummary(cpp_category_sp,
                 lldb_private::formatters::LibcxxStringSummaryProviderUTF16,
                 "std::u16string summary provider",
                 "^std::__[[:alnum:]]+::basic_string<char16_t, "
-                "std::__[[:alnum:]]+::char_traits<char16_t>, "
-                "std::__[[:alnum:]]+::allocator<char16_t> >$",
+                "std::__[[:alnum:]]+::char_traits<char16_t>,.*>$",
                 stl_summary_flags, true);
 
   AddCXXSummary(cpp_category_sp,
                 lldb_private::formatters::LibcxxStringSummaryProviderUTF32,
                 "std::u32string summary provider",
                 "^std::__[[:alnum:]]+::basic_string<char32_t, "
-                "std::__[[:alnum:]]+::char_traits<char32_t>, "
-                "std::__[[:alnum:]]+::allocator<char32_t> >$",
+                "std::__[[:alnum:]]+::char_traits<char32_t>,.*>$",
                 stl_summary_flags, true);
 
   AddCXXSummary(cpp_category_sp,
@@ -825,8 +821,7 @@ static void LoadLibCxxFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
                 lldb_private::formatters::LibcxxWStringSummaryProvider,
                 "std::wstring summary provider",
                 "^std::__[[:alnum:]]+::basic_string<wchar_t, "
-                "std::__[[:alnum:]]+::char_traits<wchar_t>, "
-                "std::__[[:alnum:]]+::allocator<wchar_t> >$",
+                "std::__[[:alnum:]]+::char_traits<wchar_t>,.*>$",
                 stl_summary_flags, true);
 
   AddCXXSummary(cpp_category_sp,
@@ -1342,24 +1337,16 @@ static void RegisterStdStringSummaryProvider(
 
   category_sp->AddTypeSummary(makeSpecifier(string_ty), summary_sp);
 
-  // std::basic_string<char>
   category_sp->AddTypeSummary(
       makeSpecifier(llvm::formatv("std::basic_string<{}>", char_ty).str()),
       summary_sp);
-  // std::basic_string<char,std::char_traits<char>,std::allocator<char> >
-  category_sp->AddTypeSummary(
-      makeSpecifier(llvm::formatv("std::basic_string<{0},std::char_traits<{0}>,"
-                                  "std::allocator<{0}> >",
-                                  char_ty)
-                        .str()),
-      summary_sp);
-  // std::basic_string<char, std::char_traits<char>, std::allocator<char> >
+
   category_sp->AddTypeSummary(
-      makeSpecifier(
-          llvm::formatv("std::basic_string<{0}, std::char_traits<{0}>, "
-                        "std::allocator<{0}> >",
+      std::make_shared<lldb_private::TypeNameSpecifierImpl>(
+          llvm::formatv("^std::basic_string<{0}, ?std::char_traits<{0}>,.*>$",
                         char_ty)
-              .str()),
+              .str(),
+          eFormatterMatchRegex),
       summary_sp);
 }
 
@@ -1382,20 +1369,17 @@ static void LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
   cpp_category_sp->AddTypeSummary("std::__cxx11::string", eFormatterMatchExact,
                                   string_summary_sp);
   cpp_category_sp->AddTypeSummary(
-      "std::__cxx11::basic_string<char, std::char_traits<char>, "
-      "std::allocator<char> >",
-      eFormatterMatchExact, string_summary_sp);
-  cpp_category_sp->AddTypeSummary("std::__cxx11::basic_string<unsigned char, "
-                                  "std::char_traits<unsigned char>, "
-                                  "std::allocator<unsigned char> >",
-                                  eFormatterMatchExact, string_summary_sp);
+      "^std::__cxx11::basic_string<char, std::char_traits<char>,.*>$",
+      eFormatterMatchRegex, string_summary_sp);
+  cpp_category_sp->AddTypeSummary("^std::__cxx11::basic_string<unsigned char, "
+                                  "std::char_traits<unsigned char>,.*>$",
+                                  eFormatterMatchRegex, string_summary_sp);
 
   cpp_category_sp->AddTypeSummary("std::__cxx11::wstring", eFormatterMatchExact,
                                   string_summary_sp);
   cpp_category_sp->AddTypeSummary(
-      "std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, "
-      "std::allocator<wchar_t> >",
-      eFormatterMatchExact, string_summary_sp);
+      "^std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>,.*>$",
+      eFormatterMatchRegex, string_summary_sp);
 
   SyntheticChildren::Flags stl_synth_flags;
   stl_synth_flags.SetCascades(true).SetSkipPointers(false).SetSkipReferences(
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/TestDataFormatterStdString.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/TestDataFormatterStdString.py
@@ -80,6 +80,8 @@ def cleanup():
                 '(%s::string) Q = "quite a long std::strin with lots of info inside it"'
                 % ns,
                 "(%s::string *) null_str = nullptr" % ns,
+                '(CustomString) custom_str = "hello!"',
+                '(CustomWString) custom_wstr = L"hello!"',
             ],
         )
 
@@ -143,6 +145,10 @@ def do_test_multibyte(self):
                 '(%s::u16string) u16_empty = u""' % ns,
                 '(%s::u32string) u32_string = U"🍄🍅🍆🍌"' % ns,
                 '(%s::u32string) u32_empty = U""' % ns,
+                '(CustomStringU16) custom_u16 = u"ß水氶"',
+                '(CustomStringU16) custom_u16_empty = u""',
+                '(CustomStringU32) custom_u32 = U"🍄🍅🍆🍌"',
+                '(CustomStringU32) custom_u32_empty = U""',
             ],
         )
 
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/main.cpp b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/string/main.cpp
@@ -1,6 +1,33 @@
+#include <cstdlib>
 #include <stdint.h>
 #include <string>
 
+template <typename T> struct CustomAlloc {
+  using value_type = T;
+  using pointer = value_type *;
+  using const_pointer = const value_type *;
+  using size_type = std::size_t;
+
+  pointer allocate(size_type n) { return (T *)malloc(n * sizeof(T)); }
+
+  void deallocate(pointer p, size_type) {
+    if (p)
+      free(p);
+  }
+};
+
+using CustomString =
+    std::basic_string<char, std::char_traits<char>, CustomAlloc<char>>;
+
+using CustomWString =
+    std::basic_string<wchar_t, std::char_traits<wchar_t>, CustomAlloc<wchar_t>>;
+
+using CustomStringU16 = std::basic_string<char16_t, std::char_traits<char16_t>,
+                                          CustomAlloc<char16_t>>;
+
+using CustomStringU32 = std::basic_string<char32_t, std::char_traits<char32_t>,
+                                          CustomAlloc<char32_t>>;
+
 size_t touch_string(std::string &in_str) {
   return in_str.size(); // Break here to look at bad string
 }
@@ -99,8 +126,16 @@ int main() {
   std::string *pq = &q;
   std::string *pQ = &Q;
 
+  CustomString custom_str("hello!");
+  CustomWString custom_wstr(L"hello!");
+  CustomStringU16 custom_u16(u16_string.c_str());
+  CustomStringU16 custom_u16_empty(u"");
+  CustomStringU32 custom_u32(u32_string.c_str());
+  CustomStringU32 custom_u32_empty(U"");
+
   S.assign(L"!!!!!"); // Set break point at this line.
   std::string *not_a_string = (std::string *)0x0;
   touch_string(*not_a_string);
+
   return 0;
 }
