[clang][Sema] Suggest/Hint Standard Library Include File #146227

Mr-Anyone · 2025-06-28T16:30:46Z

Clang now tries to suggest and hint standard library include file by emitting the following.

    4 |     std::unordered_map<std::string, std::string> map;
      |          ^~~~~~~~~~~~~
main.cpp:4:10: note: maybe try to include <unordered_map>; 'std::unordered_map' is defined in <unordered_map>
main.cpp:4:10: note: 'std::unordered_map' is a c++11 feature
main.cpp:4:42: note: maybe try to include <string>; 'std::string' is defined in <string>

This works for both C and C++.

fixes #120388

llvmbot · 2025-06-28T16:31:20Z

@llvm/pr-subscribers-clang

Author: Vincent (Mr-Anyone)

Changes

Clang now tries to suggest and hint standard library include file by emitting the following.

    4 |     std::unordered_map&lt;std::string, std::string&gt; map;
      |          ^~~~~~~~~~~~~
main.cpp:4:10: note: maybe try to include &lt;unordered_map&gt;; 'std::unordered_map' is defined in &lt;unordered_map&gt;
main.cpp:4:10: note: 'std::unordered_map' is a c++11 feature
main.cpp:4:42: note: maybe try to include &lt;string&gt;; 'std::string' is defined in &lt;string&gt;

This works for both C and C++.

fixes #120388

Patch is 644.43 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/146227.diff

26 Files Affected:

(modified) clang/docs/ReleaseNotes.rst (+1)
(modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+4)
(modified) clang/include/clang/Sema/Sema.h (+10)
(modified) clang/include/clang/Tooling/Inclusions/StandardLibrary.h (+22)
(modified) clang/lib/Parse/ParseExprCXX.cpp (+14)
(modified) clang/lib/Sema/CMakeLists.txt (+1)
(modified) clang/lib/Sema/SemaDecl.cpp (+49)
(modified) clang/lib/Sema/SemaExpr.cpp (+6)
(modified) clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc (+429-697)
(modified) clang/lib/Tooling/Inclusions/Stdlib/StandardLibrary.cpp (+55-5)
(modified) clang/lib/Tooling/Inclusions/Stdlib/StdSpecialSymbolMap.inc (-5)
(modified) clang/lib/Tooling/Inclusions/Stdlib/StdSymbolMap.inc (+2014-2140)
(modified) clang/test/Headers/stddef.c (+40-6)
(modified) clang/test/Headers/stddefneeds.c (+67-13)
(modified) clang/test/Headers/stddefneeds.cpp (+10-10)
(modified) clang/test/Modules/implicit-declared-allocation-functions.cppm (+12-6)
(modified) clang/test/Modules/macro-reexport.cpp (+3-3)
(modified) clang/test/Modules/stddef.cpp (+2-2)
(modified) clang/test/Sema/MicrosoftCompatibility.c (+1-1)
(modified) clang/test/Sema/builtin-setjmp.c (+5-3)
(modified) clang/test/Sema/c23-delayed-typo-correction-crashes.c (+2-1)
(modified) clang/test/Sema/implicit-builtin-decl.c (+2-1)
(added) clang/test/Sema/include-suggestion.c (+5)
(modified) clang/test/SemaCXX/constructor-initializer.cpp (+1-1)
(added) clang/test/SemaCXX/include-suggestions-cxx.cpp (+2458)
(modified) clang/test/SemaCXX/no-implicit-builtin-decls.cpp (+1-1)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 96477ef6ddc9a..b38dafb06e3ca 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -470,6 +470,7 @@ Improvements to Clang's diagnostics
   diagnostics. This fixes a bunch of `bool` being printed as `_Bool`, and also
   a bunch of HLSL types being printed as their C++ equivalents.
 - Clang now consistently quotes expressions in diagnostics.
+- Clang now suggest standard library include path and its associated C++ or C language version.
 - When printing types for diagnostics, clang now doesn't suppress the scopes of
   template arguments contained within nested names.
 - The ``-Wshift-bool`` warning has been added to warn about shifting a boolean. (#GH28334)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index f2f2152b8bbbe..96f444544291d 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5978,6 +5978,10 @@ def err_template_expansion_into_fixed_list : Error<
   "template|concept}0">;
 def note_parameter_type : Note<
   "parameter of type %0 is declared here">;
+def note_standard_lib_include_suggestion : Note<
+  "maybe try to include %0; '%1' is defined in %0">;
+def note_standard_lib_version : Note<
+  "'%0' is a %1 feature">;
 
 // C++11 Variadic Templates
 def err_template_param_pack_default_arg : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 9397546c8fc5d..f4c22cc255876 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -3611,6 +3611,16 @@ class Sema final : public SemaBase {
                                ParsedType &SuggestedType,
                                bool IsTemplateName = false);
 
+  // Try to suggest the missing standard library include files
+  //
+  // \param SymbolName the symbol name like 'cout'
+  // \param SourceLocation the location of the note being emitted
+  // \param Namespace the namespace that must end with ::, so like 'std::'
+  void NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                            StringRef Namespace);
+  void NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                            const CXXScopeSpec *SS);
+
   /// Attempt to behave like MSVC in situations where lookup of an unqualified
   /// type name has failed in a dependent context. In these situations, we
   /// automatically form a DependentTypeName that will retry lookup in a related
diff --git a/clang/include/clang/Tooling/Inclusions/StandardLibrary.h b/clang/include/clang/Tooling/Inclusions/StandardLibrary.h
index 147f505ade058..42bbb5b3f0d8c 100644
--- a/clang/include/clang/Tooling/Inclusions/StandardLibrary.h
+++ b/clang/include/clang/Tooling/Inclusions/StandardLibrary.h
@@ -29,6 +29,27 @@ class NamespaceDecl;
 class DeclContext;
 namespace tooling {
 namespace stdlib {
+enum Version {
+  Unknown,
+
+  // c++ versions
+  CPlusPlusStart,
+  CPlusPlus11,
+  CPlusPlus14,
+  CPlusPlus17,
+  CPlusPlus20,
+  CPlusPlus23,
+  CPlusPlus26,
+  CPlusPlusEnd,
+
+  // c version
+  CStart,
+  C99,
+  C11,
+  CEnd
+};
+
+llvm::StringRef GetAsString(Version Ver);
 
 class Symbol;
 enum class Lang { C = 0, CXX, LastValue = CXX };
@@ -85,6 +106,7 @@ class Symbol {
   std::optional<Header> header() const;
   // Some symbols may be provided by multiple headers.
   llvm::SmallVector<Header> headers() const;
+  Version version() const;
 
 private:
   Symbol(unsigned ID, Lang Language) : ID(ID), Language(Language) {}
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index 1ea0cf52933f6..9de0e9ca74c6f 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -226,6 +226,11 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
     HasScopeSpecifier = true;
   }
 
+  // If `FailedNestedNameBuilding` is true, attempt to suggest the standard
+  // include file corresponding to the current `FullNamespace` and symbol.
+  std::string FullNamespace = "";
+  bool FailedNesatedNameBuilding = false;
+
   // Preferred type might change when parsing qualifiers, we need the original.
   auto SavedType = PreferredType;
   while (true) {
@@ -454,6 +459,9 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
       // We have an identifier followed by a '::'. Lookup this name
       // as the name in a nested-name-specifier.
       Token Identifier = Tok;
+      FullNamespace += Identifier.getIdentifierInfo()->getName();
+      FullNamespace += "::";
+
       SourceLocation IdLoc = ConsumeToken();
       assert(Tok.isOneOf(tok::coloncolon, tok::colon) &&
              "NextToken() not working properly!");
@@ -465,6 +473,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
       if (Actions.ActOnCXXNestedNameSpecifier(
               getCurScope(), IdInfo, EnteringContext, SS, CorrectionFlagPtr,
               OnlyNamespace)) {
+        FailedNesatedNameBuilding = true;
         // Identifier is not recognized as a nested name, but we can have
         // mistyped '::' instead of ':'.
         if (CorrectionFlagPtr && IsCorrectedToColon) {
@@ -554,6 +563,11 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
     break;
   }
 
+  if (FailedNesatedNameBuilding && Tok.getKind() == tok::identifier) {
+    Actions.NoteStandardIncludes(Tok.getIdentifierInfo()->getName(),
+                                 Tok.getLocation(), FullNamespace);
+  }
+
   // Even if we didn't see any pieces of a nested-name-specifier, we
   // still check whether there is a tilde in this position, which
   // indicates a potential pseudo-destructor.
diff --git a/clang/lib/Sema/CMakeLists.txt b/clang/lib/Sema/CMakeLists.txt
index 51e0ee10b080b..ff4f583bdd9bf 100644
--- a/clang/lib/Sema/CMakeLists.txt
+++ b/clang/lib/Sema/CMakeLists.txt
@@ -115,4 +115,5 @@ add_clang_library(clangSema
   clangEdit
   clangLex
   clangSupport
+  clangToolingInclusionsStdlib
   )
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index e1cccf068b5aa..7d659a6d06f93 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -58,10 +58,12 @@
 #include "clang/Sema/SemaSwift.h"
 #include "clang/Sema/SemaWasm.h"
 #include "clang/Sema/Template.h"
+#include "clang/Tooling/Inclusions/StandardLibrary.h"
 #include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Frontend/HLSL/HLSLRootSignature.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/TargetParser/Triple.h"
@@ -805,6 +807,52 @@ void Sema::DiagnoseUnknownTypeName(IdentifierInfo *&II,
     assert(SS && SS->isInvalid() &&
            "Invalid scope specifier has already been diagnosed");
   }
+
+  // don't note standard include files for OpenCL and Objective C
+  if ((getLangOpts().CPlusPlus || getLangOpts().C99) && !getLangOpts().OpenCL &&
+      !getLangOpts().ObjC)
+    NoteStandardIncludes(II->getName(), IILoc, SS);
+}
+
+void Sema::NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                                StringRef Namespace) {
+  using clang::tooling::stdlib::Lang;
+
+  llvm::StringRef HeaderName = "";
+  tooling::stdlib::Lang LangOption = tooling::stdlib::Lang::C;
+  if (getLangOpts().CPlusPlus)
+    LangOption = clang::tooling::stdlib::Lang::CXX;
+
+  if (auto StdSym =
+          tooling::stdlib::Symbol::named(Namespace, SymbolName, LangOption)) {
+    if (auto Header = StdSym->header()) {
+      HeaderName = Header->name();
+      Diag(IILoc, diag::note_standard_lib_include_suggestion)
+          << HeaderName << (Namespace + SymbolName).str();
+
+      // Noting the C/C++ version as well
+      if (StdSym->version() != tooling::stdlib::Unknown) {
+        llvm::StringRef CPlusPlusVersion =
+            tooling::stdlib::GetAsString(StdSym->version());
+
+        Diag(IILoc, diag::note_standard_lib_version)
+            << (Namespace + SymbolName).str() << CPlusPlusVersion;
+      }
+    }
+  }
+}
+
+void Sema::NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                                const CXXScopeSpec *SS) {
+  std::string Namespace = "";
+  if (SS) {
+    llvm::raw_string_ostream Stream(Namespace);
+    if (SS->isValid())
+      SS->getScopeRep()->dump(Stream);
+    Stream.flush();
+  }
+
+  NoteStandardIncludes(SymbolName, IILoc, Namespace);
 }
 
 /// Determine whether the given result set contains either a type name
@@ -16784,6 +16832,7 @@ NamedDecl *Sema::ImplicitlyDefineFunction(SourceLocation Loc,
   }
 
   Diag(Loc, diag_id) << &II;
+  NoteStandardIncludes(II.getName(), Loc, "");
   if (Corrected) {
     // If the correction is going to suggest an implicitly defined function,
     // skip the correction as not being a particularly good idea.
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index fc2819458a4ff..9015b70deb5d1 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -2660,11 +2660,17 @@ bool Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
   if (!SS.isEmpty()) {
     Diag(R.getNameLoc(), diag::err_no_member)
         << Name << computeDeclContext(SS, false) << NameRange;
+    NoteStandardIncludes(Name.getAsString(), R.getNameLoc(), &SS);
     return true;
   }
 
   // Give up, we can't recover.
   Diag(R.getNameLoc(), diagnostic) << Name << NameRange;
+
+  // don't note standard include files for OpenCL and Objective C
+  if ((getLangOpts().CPlusPlus || getLangOpts().C99) && !getLangOpts().OpenCL &&
+      !getLangOpts().ObjC)
+    NoteStandardIncludes(Name.getAsString(), R.getNameLoc(), /*Namespace=*/"");
   return true;
 }
 
diff --git a/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc b/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
index 463ce921f0672..b3a1921f3c74b 100644
--- a/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
+++ b/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
@@ -6,246 +6,44 @@
 // This file was generated automatically by
 // clang/tools/include-mapping/gen_std.py, DO NOT EDIT!
 //
-// Generated from cppreference offline HTML book (modified on 2018-10-28).
+// Generated from cppreference offline HTML book (modified on 2025-02-10).
 //===----------------------------------------------------------------------===//
 
-SYMBOL(ATOMIC_BOOL_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_CHAR16_T_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_CHAR32_T_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_CHAR_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_FLAG_INIT, None, <stdatomic.h>)
-SYMBOL(ATOMIC_INT_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_LLONG_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_LONG_LOGK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_POINTER_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_SHORT_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_VAR_INIT, None, <stdatomic.h>)
-SYMBOL(ATOMIC_WCHAR_T_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(BUFSIZ, None, <stdio.h>)
-SYMBOL(CHAR_BIT, None, <limits.h>)
-SYMBOL(CHAR_MAX, None, <limits.h>)
-SYMBOL(CHAR_MIN, None, <limits.h>)
-SYMBOL(CLOCKS_PER_SEC, None, <time.h>)
-SYMBOL(CMPLX, None, <complex.h>)
-SYMBOL(CMPLXF, None, <complex.h>)
-SYMBOL(CMPLXL, None, <complex.h>)
-SYMBOL(DBL_DECIMAL_DIG, None, <float.h>)
-SYMBOL(DBL_DIG, None, <float.h>)
-SYMBOL(DBL_EPSILON, None, <float.h>)
-SYMBOL(DBL_HAS_SUBNORM, None, <float.h>)
-SYMBOL(DBL_MANT_DIG, None, <float.h>)
-SYMBOL(DBL_MAX, None, <float.h>)
-SYMBOL(DBL_MAX_10_EXP, None, <float.h>)
-SYMBOL(DBL_MAX_EXP, None, <float.h>)
-SYMBOL(DBL_MIN, None, <float.h>)
-SYMBOL(DBL_MIN_10_EXP, None, <float.h>)
-SYMBOL(DBL_MIN_EXP, None, <float.h>)
-SYMBOL(DBL_TRUE_MIN, None, <float.h>)
-SYMBOL(DECIMAL_DIG, None, <float.h>)
-SYMBOL(EDOM, None, <errno.h>)
-SYMBOL(EILSEQ, None, <errno.h>)
-SYMBOL(EOF, None, <stdio.h>)
-SYMBOL(ERANGE, None, <errno.h>)
-SYMBOL(EXIT_FAILURE, None, <stdlib.h>)
-SYMBOL(EXIT_SUCCESS, None, <stdlib.h>)
-SYMBOL(FE_ALL_EXCEPT, None, <fenv.h>)
-SYMBOL(FE_DFL_ENV, None, <fenv.h>)
-SYMBOL(FE_DIVBYZERO, None, <fenv.h>)
-SYMBOL(FE_DOWNWARD, None, <fenv.h>)
-SYMBOL(FE_INEXACT, None, <fenv.h>)
-SYMBOL(FE_INVALID, None, <fenv.h>)
-SYMBOL(FE_OVERFLOW, None, <fenv.h>)
-SYMBOL(FE_TONEAREST, None, <fenv.h>)
-SYMBOL(FE_TOWARDZERO, None, <fenv.h>)
-SYMBOL(FE_UNDERFLOW, None, <fenv.h>)
-SYMBOL(FE_UPWARD, None, <fenv.h>)
 SYMBOL(FILE, None, <stdio.h>)
-SYMBOL(FILENAME_MAX, None, <stdio.h>)
-SYMBOL(FLT_DECIMAL_DIG, None, <float.h>)
-SYMBOL(FLT_DIG, None, <float.h>)
-SYMBOL(FLT_EPSILON, None, <float.h>)
-SYMBOL(FLT_EVAL_METHOD, None, <float.h>)
-SYMBOL(FLT_HAS_SUBNORM, None, <float.h>)
-SYMBOL(FLT_MANT_DIG, None, <float.h>)
-SYMBOL(FLT_MAX, None, <float.h>)
-SYMBOL(FLT_MAX_10_EXP, None, <float.h>)
-SYMBOL(FLT_MAX_EXP, None, <float.h>)
-SYMBOL(FLT_MIN, None, <float.h>)
-SYMBOL(FLT_MIN_10_EXP, None, <float.h>)
-SYMBOL(FLT_MIN_EXP, None, <float.h>)
-SYMBOL(FLT_RADIX, None, <float.h>)
-SYMBOL(FLT_ROUNDS, None, <float.h>)
-SYMBOL(FLT_TRUE_MIN, None, <float.h>)
-SYMBOL(FOPEN_MAX, None, <stdio.h>)
-SYMBOL(FP_INFINITE, None, <math.h>)
-SYMBOL(FP_NAN, None, <math.h>)
-SYMBOL(FP_NORNAL, None, <math.h>)
-SYMBOL(FP_SUBNORMAL, None, <math.h>)
-SYMBOL(FP_ZERO, None, <math.h>)
-SYMBOL(HUGE_VAL, None, <math.h>)
-SYMBOL(HUGE_VALF, None, <math.h>)
-SYMBOL(HUGE_VALL, None, <math.h>)
-SYMBOL(I, None, <complex.h>)
-SYMBOL(INFINITY, None, <math.h>)
-SYMBOL(INT16_MAX, None, <stdint.h>)
-SYMBOL(INT16_MIN, None, <stdint.h>)
-SYMBOL(INT32_MAX, None, <stdint.h>)
-SYMBOL(INT32_MIN, None, <stdint.h>)
-SYMBOL(INT64_MAX, None, <stdint.h>)
-SYMBOL(INT64_MIN, None, <stdint.h>)
-SYMBOL(INT8_MAX, None, <stdint.h>)
-SYMBOL(INT8_MIN, None, <stdint.h>)
-SYMBOL(INTMAX_MAX, None, <stdint.h>)
-SYMBOL(INTMAX_MIN, None, <stdint.h>)
-SYMBOL(INTPTR_MAX, None, <stdint.h>)
-SYMBOL(INTPTR_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST16_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST16_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST32_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST32_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST64_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST64_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST8_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST8_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST16_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST16_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST32_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST32_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST64_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST64_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST8_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST8_MIN, None, <stdint.h>)
-SYMBOL(INT_MAX, None, <limits.h>)
-SYMBOL(INT_MIN, None, <limits.h>)
-SYMBOL(LC_ALL, None, <locale.h>)
-SYMBOL(LC_COLLATE, None, <locale.h>)
-SYMBOL(LC_CTYPE, None, <locale.h>)
-SYMBOL(LC_MONETARY, None, <locale.h>)
-SYMBOL(LC_NUMERIC, None, <locale.h>)
-SYMBOL(LC_TIME, None, <locale.h>)
-SYMBOL(LDBL_DECIMAL_DIG, None, <float.h>)
-SYMBOL(LDBL_DIG, None, <float.h>)
-SYMBOL(LDBL_EPSILON, None, <float.h>)
-SYMBOL(LDBL_HAS_SUBNORM, None, <float.h>)
-SYMBOL(LDBL_MANT_DIG, None, <float.h>)
-SYMBOL(LDBL_MAX, None, <float.h>)
-SYMBOL(LDBL_MAX_10_EXP, None, <float.h>)
-SYMBOL(LDBL_MAX_EXP, None, <float.h>)
-SYMBOL(LDBL_MIN, None, <float.h>)
-SYMBOL(LDBL_MIN_10_EXP, None, <float.h>)
-SYMBOL(LDBL_MIN_EXP, None, <float.h>)
-SYMBOL(LDBL_TRUE_MIN, None, <float.h>)
-SYMBOL(LLONG_MAX, None, <limits.h>)
-SYMBOL(LLONG_MIN, None, <limits.h>)
-SYMBOL(LONG_MAX, None, <limits.h>)
-SYMBOL(LONG_MIN, None, <limits.h>)
-SYMBOL(L_tmpnam, None, <stdio.h>)
-SYMBOL(L_tmpnam_s, None, <stdio.h>)
-SYMBOL(MATH_ERREXCEPT, None, <math.h>)
-SYMBOL(MATH_ERRNO, None, <math.h>)
-SYMBOL(MB_CUR_MAX, None, <stdlib.h>)
-SYMBOL(MB_LEN_MAX, None, <limits.h>)
-SYMBOL(NAN, None, <math.h>)
-SYMBOL(ONCE_FLAG_INIT, None, <threads.h>)
-SYMBOL(PTRDIFF_MAX, None, <stdint.h>)
-SYMBOL(PTRDIFF_MIN, None, <stdint.h>)
-SYMBOL(RAND_MAX, None, <stdlib.h>)
-SYMBOL(RSIZE_MAX, None, <stdint.h>)
-SYMBOL(SCHAR_MAX, None, <limits.h>)
-SYMBOL(SCHAR_MIN, None, <limits.h>)
-SYMBOL(SEEK_CUR, None, <stdio.h>)
-SYMBOL(SEEK_END, None, <stdio.h>)
-SYMBOL(SEEK_SET, None, <stdio.h>)
-SYMBOL(SHRT_MAX, None, <limits.h>)
-SYMBOL(SHRT_MIN, None, <limits.h>)
-SYMBOL(SIGABRT, None, <signal.h>)
-SYMBOL(SIGFPE, None, <signal.h>)
-SYMBOL(SIGILL, None, <signal.h>)
-SYMBOL(SIGINT, None, <signal.h>)
-SYMBOL(SIGSEGV, None, <signal.h>)
-SYMBOL(SIGTERM, None, <signal.h>)
-SYMBOL(SIG_ATOMIC_MAX, None, <stdint.h>)
-SYMBOL(SIG_ATOMIC_MIN, None, <stdint.h>)
-SYMBOL(SIG_DFL, None, <signal.h>)
-SYMBOL(SIG_ERR, None, <signal.h>)
-SYMBOL(SIG_IGN, None, <signal.h>)
-SYMBOL(SIZE_MAX, None, <stdint.h>)
-SYMBOL(TIME_UTC, None, <time.h>)
-SYMBOL(TMP_MAX, None, <stdio.h>)
-SYMBOL(TMP_MAX_S, None, <stdio.h>)
-SYMBOL(TSS_DTOR_ITERATIONS, None, <threads.h>)
-SYMBOL(UCHAR_MAX, None, <limits.h>)
-SYMBOL(UINT16_MAX, None, <stdint.h>)
-SYMBOL(UINT32_MAX, None, <stdint.h>)
-SYMBOL(UINT64_MAX, None, <stdint.h>)
-SYMBOL(UINT8_MAX, None, <stdint.h>)
-SYMBOL(UINTMAX_MAX, None, <stdint.h>)
-SYMBOL(UINTPTR_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST16_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST32_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST64_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST8_MAX, None, <stdint.h>)
-SYMBOL(UINT_LEAST16_MAX, None, <stdint.h>)
-SYMBOL(UINT_LEAST32_MAX, None, <stdint.h>)
-SYMBOL(UINT_LEAST64_MAX, None, <stdint.h>)
-SYMBOL(UINT_LEAST8_MAX, None, <stdint.h>)
-SYMBOL(UINT_MAX, None, <limits.h>)
-SYMBOL(ULLONG_MAX, None, <limits.h>)
-SYMBOL(ULONG_MAX, None, <limits.h>)
-SYMBOL(USHRT_MAX, None, <limits.h>)
-SYMBOL(WCHAR_MAX, None, <wchar.h>)
-SYMBOL(WCHAR_MIN, None, <wchar.h>)
-SYMBOL(WEOF, None, <wchar.h>)
-SYMBOL(WINT_MAX, None, <stdint.h>)
-SYMBOL(WINT_MIN, None, <stdint.h>)
-SYMBOL(_Complex_I, None, <complex.h>)
-SYMBOL(_IOFBF, None, <stdio.h>)
-SYMBOL(_IOLBF, None, <stdio.h>)
-SYMBOL(_IONBF, None, <stdio.h>)
-SYMBOL(_Imaginary_I, None, <complex.h>)
-SYMBOL(__alignas_is_defined, None, <stdalign.h>)
-SYMBOL(__alignof_is_defined, None, <stdalign.h>)
-SYMBOL(abort_handler_s, None, <stdlib.h>)
+SYMBOL_VERSION(_Exit, None, <stdlib.h>, c99)
+SYMBOL(abort, None, <stdlib.h>)
+SYMBOL_VERSION(abort_handler_s, None, <stdlib.h>, c11)
 SYMBOL(abs, None, <stdlib.h>)
 SYMBOL(acos, None, <math.h>)
-SYMBOL(acosf, None, <math.h>)
-SYMBOL(acosh, None, <math.h>)
-SYMBOL(acoshf, None, <math.h>)
-SYMBOL(acoshl, None, <math.h>)
-SYMBOL(acosl, None, <math.h>)
-SYMBOL(alignas, None, <stdalign.h>)
-SYMBOL(aligned_alloc, None, <stdlib.h>)
-SYMBOL(alignof, None, <stdalign.h>)
-SYMBOL(and, None, <iso646.h>)
-SYMBOL(and_eq, None, <iso646.h>)
+SYMBOL_VERSION(acosf, None, <math.h>, c99)
+SYMBOL_VERSION(acosh, None, <math.h>, c99)
+SYMBOL_VERSION(acoshf, None, <math.h>, c99)
+SYMBOL_VERSION(acoshl, None, <math.h>, c99)
+SYMBOL_VERSION(acosl, None, <math.h>, c99)
+SYMBOL_VERSION(aligned_alloc, None, <stdlib.h>, c11)
 SYMBOL(asctime, None, <time.h>)
-SYMBOL(asctime_s, None, <time.h>)
+SYMBOL_VERSION(asctime_s, None, <time.h>, c11)
 SYMBOL(asin, None, <math.h>)
-SYMBOL(asinf, None, <math.h>)
-SYMBOL(asinh, None, <math.h>)
-SYMBOL(asinhf, None, <math.h>)
-SYMBOL(asinhl, None, <math.h>)
-SYMBOL(asinl, None, <math.h>)
-SYMBOL(assert, None, <assert.h>)
-SYMBOL(at_quick_exit, None, <stdlib.h>)
+SYMBOL_VERSION(asinf, None, <math.h>, c99)
+SYMBOL_VERSION(asinh, None, <math.h>, c99)
+SYMBOL_VERSION(asinhf, None, <math.h>, c99)
+SYMBOL_VERSION(asinhl, None, <math.h>, c99)
+SYMBOL_VERSION(asinl, None, <math.h>, c99)
+SYMBOL_VERSION(at_quick_exit, None, <stdlib.h>, c11)
 SYMBOL(atan, None, <math.h>)
 SYMBOL(atan2, None, <math.h>)
-SYMBOL(atan2f, None, <math.h>)
-SYMBOL(atan2l, None, <math.h>)
-SYMBOL(atanf, None, <math.h>)
-SYMBOL(atanh, None, <math.h>)
-SYMBOL(atanhf, None, <math.h>)
-SYMBOL(atanhl, None, <math.h>)
-SYMBOL(atanl, None, <math.h>)
+SYMBOL_VERSION(atan2f, None, <math.h>, c99)
+SYMBOL_VERSION(atan2l, None, <math.h>, c99)
+SYMBOL_VERSION(atanf, None, <math.h>, c99)
+SYMBOL_VERSION(atanh, None, <math.h>, c99)
+SYMBOL_VERSION(atanhf, None, <math.h>, c99)
+SYMBOL_VERSION(atanhl, None, <math.h>, c99)
+SYMBOL_VERSION(atanl, None, <math.h>, c99)
 SYMBOL(atexit, None, <stdlib.h>)
 SYMBOL(atof, None, <stdlib.h>)
 SYMBOL(atoi, None, <stdlib.h>)
 SYMBOL(atol, None, <stdlib.h>)
-SYMBOL(atoll, None, <stdlib.h>)
-SYMBOL(atomic_bool, None, <stdatomic.h>)
-SYMBOL(atomic_char, None, <stdatomic.h>)
-SYMBOL(atomic_char16_t, None, <stdatomic.h>)
-SYMBOL(atomic_char32_t, None, <stdatomic.h>)
+SYMBOL_VERSION(atoll,...
[truncated]

llvmbot · 2025-06-28T16:31:20Z

@llvm/pr-subscribers-clang-modules

Author: Vincent (Mr-Anyone)

Changes

Clang now tries to suggest and hint standard library include file by emitting the following.

    4 |     std::unordered_map&lt;std::string, std::string&gt; map;
      |          ^~~~~~~~~~~~~
main.cpp:4:10: note: maybe try to include &lt;unordered_map&gt;; 'std::unordered_map' is defined in &lt;unordered_map&gt;
main.cpp:4:10: note: 'std::unordered_map' is a c++11 feature
main.cpp:4:42: note: maybe try to include &lt;string&gt;; 'std::string' is defined in &lt;string&gt;

This works for both C and C++.

fixes #120388

Patch is 644.43 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/146227.diff

26 Files Affected:

(modified) clang/docs/ReleaseNotes.rst (+1)
(modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+4)
(modified) clang/include/clang/Sema/Sema.h (+10)
(modified) clang/include/clang/Tooling/Inclusions/StandardLibrary.h (+22)
(modified) clang/lib/Parse/ParseExprCXX.cpp (+14)
(modified) clang/lib/Sema/CMakeLists.txt (+1)
(modified) clang/lib/Sema/SemaDecl.cpp (+49)
(modified) clang/lib/Sema/SemaExpr.cpp (+6)
(modified) clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc (+429-697)
(modified) clang/lib/Tooling/Inclusions/Stdlib/StandardLibrary.cpp (+55-5)
(modified) clang/lib/Tooling/Inclusions/Stdlib/StdSpecialSymbolMap.inc (-5)
(modified) clang/lib/Tooling/Inclusions/Stdlib/StdSymbolMap.inc (+2014-2140)
(modified) clang/test/Headers/stddef.c (+40-6)
(modified) clang/test/Headers/stddefneeds.c (+67-13)
(modified) clang/test/Headers/stddefneeds.cpp (+10-10)
(modified) clang/test/Modules/implicit-declared-allocation-functions.cppm (+12-6)
(modified) clang/test/Modules/macro-reexport.cpp (+3-3)
(modified) clang/test/Modules/stddef.cpp (+2-2)
(modified) clang/test/Sema/MicrosoftCompatibility.c (+1-1)
(modified) clang/test/Sema/builtin-setjmp.c (+5-3)
(modified) clang/test/Sema/c23-delayed-typo-correction-crashes.c (+2-1)
(modified) clang/test/Sema/implicit-builtin-decl.c (+2-1)
(added) clang/test/Sema/include-suggestion.c (+5)
(modified) clang/test/SemaCXX/constructor-initializer.cpp (+1-1)
(added) clang/test/SemaCXX/include-suggestions-cxx.cpp (+2458)
(modified) clang/test/SemaCXX/no-implicit-builtin-decls.cpp (+1-1)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 96477ef6ddc9a..b38dafb06e3ca 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -470,6 +470,7 @@ Improvements to Clang's diagnostics
   diagnostics. This fixes a bunch of `bool` being printed as `_Bool`, and also
   a bunch of HLSL types being printed as their C++ equivalents.
 - Clang now consistently quotes expressions in diagnostics.
+- Clang now suggest standard library include path and its associated C++ or C language version.
 - When printing types for diagnostics, clang now doesn't suppress the scopes of
   template arguments contained within nested names.
 - The ``-Wshift-bool`` warning has been added to warn about shifting a boolean. (#GH28334)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index f2f2152b8bbbe..96f444544291d 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5978,6 +5978,10 @@ def err_template_expansion_into_fixed_list : Error<
   "template|concept}0">;
 def note_parameter_type : Note<
   "parameter of type %0 is declared here">;
+def note_standard_lib_include_suggestion : Note<
+  "maybe try to include %0; '%1' is defined in %0">;
+def note_standard_lib_version : Note<
+  "'%0' is a %1 feature">;
 
 // C++11 Variadic Templates
 def err_template_param_pack_default_arg : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 9397546c8fc5d..f4c22cc255876 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -3611,6 +3611,16 @@ class Sema final : public SemaBase {
                                ParsedType &SuggestedType,
                                bool IsTemplateName = false);
 
+  // Try to suggest the missing standard library include files
+  //
+  // \param SymbolName the symbol name like 'cout'
+  // \param SourceLocation the location of the note being emitted
+  // \param Namespace the namespace that must end with ::, so like 'std::'
+  void NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                            StringRef Namespace);
+  void NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                            const CXXScopeSpec *SS);
+
   /// Attempt to behave like MSVC in situations where lookup of an unqualified
   /// type name has failed in a dependent context. In these situations, we
   /// automatically form a DependentTypeName that will retry lookup in a related
diff --git a/clang/include/clang/Tooling/Inclusions/StandardLibrary.h b/clang/include/clang/Tooling/Inclusions/StandardLibrary.h
index 147f505ade058..42bbb5b3f0d8c 100644
--- a/clang/include/clang/Tooling/Inclusions/StandardLibrary.h
+++ b/clang/include/clang/Tooling/Inclusions/StandardLibrary.h
@@ -29,6 +29,27 @@ class NamespaceDecl;
 class DeclContext;
 namespace tooling {
 namespace stdlib {
+enum Version {
+  Unknown,
+
+  // c++ versions
+  CPlusPlusStart,
+  CPlusPlus11,
+  CPlusPlus14,
+  CPlusPlus17,
+  CPlusPlus20,
+  CPlusPlus23,
+  CPlusPlus26,
+  CPlusPlusEnd,
+
+  // c version
+  CStart,
+  C99,
+  C11,
+  CEnd
+};
+
+llvm::StringRef GetAsString(Version Ver);
 
 class Symbol;
 enum class Lang { C = 0, CXX, LastValue = CXX };
@@ -85,6 +106,7 @@ class Symbol {
   std::optional<Header> header() const;
   // Some symbols may be provided by multiple headers.
   llvm::SmallVector<Header> headers() const;
+  Version version() const;
 
 private:
   Symbol(unsigned ID, Lang Language) : ID(ID), Language(Language) {}
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index 1ea0cf52933f6..9de0e9ca74c6f 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -226,6 +226,11 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
     HasScopeSpecifier = true;
   }
 
+  // If `FailedNestedNameBuilding` is true, attempt to suggest the standard
+  // include file corresponding to the current `FullNamespace` and symbol.
+  std::string FullNamespace = "";
+  bool FailedNesatedNameBuilding = false;
+
   // Preferred type might change when parsing qualifiers, we need the original.
   auto SavedType = PreferredType;
   while (true) {
@@ -454,6 +459,9 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
       // We have an identifier followed by a '::'. Lookup this name
       // as the name in a nested-name-specifier.
       Token Identifier = Tok;
+      FullNamespace += Identifier.getIdentifierInfo()->getName();
+      FullNamespace += "::";
+
       SourceLocation IdLoc = ConsumeToken();
       assert(Tok.isOneOf(tok::coloncolon, tok::colon) &&
              "NextToken() not working properly!");
@@ -465,6 +473,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
       if (Actions.ActOnCXXNestedNameSpecifier(
               getCurScope(), IdInfo, EnteringContext, SS, CorrectionFlagPtr,
               OnlyNamespace)) {
+        FailedNesatedNameBuilding = true;
         // Identifier is not recognized as a nested name, but we can have
         // mistyped '::' instead of ':'.
         if (CorrectionFlagPtr && IsCorrectedToColon) {
@@ -554,6 +563,11 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
     break;
   }
 
+  if (FailedNesatedNameBuilding && Tok.getKind() == tok::identifier) {
+    Actions.NoteStandardIncludes(Tok.getIdentifierInfo()->getName(),
+                                 Tok.getLocation(), FullNamespace);
+  }
+
   // Even if we didn't see any pieces of a nested-name-specifier, we
   // still check whether there is a tilde in this position, which
   // indicates a potential pseudo-destructor.
diff --git a/clang/lib/Sema/CMakeLists.txt b/clang/lib/Sema/CMakeLists.txt
index 51e0ee10b080b..ff4f583bdd9bf 100644
--- a/clang/lib/Sema/CMakeLists.txt
+++ b/clang/lib/Sema/CMakeLists.txt
@@ -115,4 +115,5 @@ add_clang_library(clangSema
   clangEdit
   clangLex
   clangSupport
+  clangToolingInclusionsStdlib
   )
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index e1cccf068b5aa..7d659a6d06f93 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -58,10 +58,12 @@
 #include "clang/Sema/SemaSwift.h"
 #include "clang/Sema/SemaWasm.h"
 #include "clang/Sema/Template.h"
+#include "clang/Tooling/Inclusions/StandardLibrary.h"
 #include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Frontend/HLSL/HLSLRootSignature.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/TargetParser/Triple.h"
@@ -805,6 +807,52 @@ void Sema::DiagnoseUnknownTypeName(IdentifierInfo *&II,
     assert(SS && SS->isInvalid() &&
            "Invalid scope specifier has already been diagnosed");
   }
+
+  // don't note standard include files for OpenCL and Objective C
+  if ((getLangOpts().CPlusPlus || getLangOpts().C99) && !getLangOpts().OpenCL &&
+      !getLangOpts().ObjC)
+    NoteStandardIncludes(II->getName(), IILoc, SS);
+}
+
+void Sema::NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                                StringRef Namespace) {
+  using clang::tooling::stdlib::Lang;
+
+  llvm::StringRef HeaderName = "";
+  tooling::stdlib::Lang LangOption = tooling::stdlib::Lang::C;
+  if (getLangOpts().CPlusPlus)
+    LangOption = clang::tooling::stdlib::Lang::CXX;
+
+  if (auto StdSym =
+          tooling::stdlib::Symbol::named(Namespace, SymbolName, LangOption)) {
+    if (auto Header = StdSym->header()) {
+      HeaderName = Header->name();
+      Diag(IILoc, diag::note_standard_lib_include_suggestion)
+          << HeaderName << (Namespace + SymbolName).str();
+
+      // Noting the C/C++ version as well
+      if (StdSym->version() != tooling::stdlib::Unknown) {
+        llvm::StringRef CPlusPlusVersion =
+            tooling::stdlib::GetAsString(StdSym->version());
+
+        Diag(IILoc, diag::note_standard_lib_version)
+            << (Namespace + SymbolName).str() << CPlusPlusVersion;
+      }
+    }
+  }
+}
+
+void Sema::NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,
+                                const CXXScopeSpec *SS) {
+  std::string Namespace = "";
+  if (SS) {
+    llvm::raw_string_ostream Stream(Namespace);
+    if (SS->isValid())
+      SS->getScopeRep()->dump(Stream);
+    Stream.flush();
+  }
+
+  NoteStandardIncludes(SymbolName, IILoc, Namespace);
 }
 
 /// Determine whether the given result set contains either a type name
@@ -16784,6 +16832,7 @@ NamedDecl *Sema::ImplicitlyDefineFunction(SourceLocation Loc,
   }
 
   Diag(Loc, diag_id) << &II;
+  NoteStandardIncludes(II.getName(), Loc, "");
   if (Corrected) {
     // If the correction is going to suggest an implicitly defined function,
     // skip the correction as not being a particularly good idea.
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index fc2819458a4ff..9015b70deb5d1 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -2660,11 +2660,17 @@ bool Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
   if (!SS.isEmpty()) {
     Diag(R.getNameLoc(), diag::err_no_member)
         << Name << computeDeclContext(SS, false) << NameRange;
+    NoteStandardIncludes(Name.getAsString(), R.getNameLoc(), &SS);
     return true;
   }
 
   // Give up, we can't recover.
   Diag(R.getNameLoc(), diagnostic) << Name << NameRange;
+
+  // don't note standard include files for OpenCL and Objective C
+  if ((getLangOpts().CPlusPlus || getLangOpts().C99) && !getLangOpts().OpenCL &&
+      !getLangOpts().ObjC)
+    NoteStandardIncludes(Name.getAsString(), R.getNameLoc(), /*Namespace=*/"");
   return true;
 }
 
diff --git a/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc b/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
index 463ce921f0672..b3a1921f3c74b 100644
--- a/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
+++ b/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
@@ -6,246 +6,44 @@
 // This file was generated automatically by
 // clang/tools/include-mapping/gen_std.py, DO NOT EDIT!
 //
-// Generated from cppreference offline HTML book (modified on 2018-10-28).
+// Generated from cppreference offline HTML book (modified on 2025-02-10).
 //===----------------------------------------------------------------------===//
 
-SYMBOL(ATOMIC_BOOL_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_CHAR16_T_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_CHAR32_T_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_CHAR_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_FLAG_INIT, None, <stdatomic.h>)
-SYMBOL(ATOMIC_INT_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_LLONG_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_LONG_LOGK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_POINTER_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_SHORT_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(ATOMIC_VAR_INIT, None, <stdatomic.h>)
-SYMBOL(ATOMIC_WCHAR_T_LOCK_FREE, None, <stdatomic.h>)
-SYMBOL(BUFSIZ, None, <stdio.h>)
-SYMBOL(CHAR_BIT, None, <limits.h>)
-SYMBOL(CHAR_MAX, None, <limits.h>)
-SYMBOL(CHAR_MIN, None, <limits.h>)
-SYMBOL(CLOCKS_PER_SEC, None, <time.h>)
-SYMBOL(CMPLX, None, <complex.h>)
-SYMBOL(CMPLXF, None, <complex.h>)
-SYMBOL(CMPLXL, None, <complex.h>)
-SYMBOL(DBL_DECIMAL_DIG, None, <float.h>)
-SYMBOL(DBL_DIG, None, <float.h>)
-SYMBOL(DBL_EPSILON, None, <float.h>)
-SYMBOL(DBL_HAS_SUBNORM, None, <float.h>)
-SYMBOL(DBL_MANT_DIG, None, <float.h>)
-SYMBOL(DBL_MAX, None, <float.h>)
-SYMBOL(DBL_MAX_10_EXP, None, <float.h>)
-SYMBOL(DBL_MAX_EXP, None, <float.h>)
-SYMBOL(DBL_MIN, None, <float.h>)
-SYMBOL(DBL_MIN_10_EXP, None, <float.h>)
-SYMBOL(DBL_MIN_EXP, None, <float.h>)
-SYMBOL(DBL_TRUE_MIN, None, <float.h>)
-SYMBOL(DECIMAL_DIG, None, <float.h>)
-SYMBOL(EDOM, None, <errno.h>)
-SYMBOL(EILSEQ, None, <errno.h>)
-SYMBOL(EOF, None, <stdio.h>)
-SYMBOL(ERANGE, None, <errno.h>)
-SYMBOL(EXIT_FAILURE, None, <stdlib.h>)
-SYMBOL(EXIT_SUCCESS, None, <stdlib.h>)
-SYMBOL(FE_ALL_EXCEPT, None, <fenv.h>)
-SYMBOL(FE_DFL_ENV, None, <fenv.h>)
-SYMBOL(FE_DIVBYZERO, None, <fenv.h>)
-SYMBOL(FE_DOWNWARD, None, <fenv.h>)
-SYMBOL(FE_INEXACT, None, <fenv.h>)
-SYMBOL(FE_INVALID, None, <fenv.h>)
-SYMBOL(FE_OVERFLOW, None, <fenv.h>)
-SYMBOL(FE_TONEAREST, None, <fenv.h>)
-SYMBOL(FE_TOWARDZERO, None, <fenv.h>)
-SYMBOL(FE_UNDERFLOW, None, <fenv.h>)
-SYMBOL(FE_UPWARD, None, <fenv.h>)
 SYMBOL(FILE, None, <stdio.h>)
-SYMBOL(FILENAME_MAX, None, <stdio.h>)
-SYMBOL(FLT_DECIMAL_DIG, None, <float.h>)
-SYMBOL(FLT_DIG, None, <float.h>)
-SYMBOL(FLT_EPSILON, None, <float.h>)
-SYMBOL(FLT_EVAL_METHOD, None, <float.h>)
-SYMBOL(FLT_HAS_SUBNORM, None, <float.h>)
-SYMBOL(FLT_MANT_DIG, None, <float.h>)
-SYMBOL(FLT_MAX, None, <float.h>)
-SYMBOL(FLT_MAX_10_EXP, None, <float.h>)
-SYMBOL(FLT_MAX_EXP, None, <float.h>)
-SYMBOL(FLT_MIN, None, <float.h>)
-SYMBOL(FLT_MIN_10_EXP, None, <float.h>)
-SYMBOL(FLT_MIN_EXP, None, <float.h>)
-SYMBOL(FLT_RADIX, None, <float.h>)
-SYMBOL(FLT_ROUNDS, None, <float.h>)
-SYMBOL(FLT_TRUE_MIN, None, <float.h>)
-SYMBOL(FOPEN_MAX, None, <stdio.h>)
-SYMBOL(FP_INFINITE, None, <math.h>)
-SYMBOL(FP_NAN, None, <math.h>)
-SYMBOL(FP_NORNAL, None, <math.h>)
-SYMBOL(FP_SUBNORMAL, None, <math.h>)
-SYMBOL(FP_ZERO, None, <math.h>)
-SYMBOL(HUGE_VAL, None, <math.h>)
-SYMBOL(HUGE_VALF, None, <math.h>)
-SYMBOL(HUGE_VALL, None, <math.h>)
-SYMBOL(I, None, <complex.h>)
-SYMBOL(INFINITY, None, <math.h>)
-SYMBOL(INT16_MAX, None, <stdint.h>)
-SYMBOL(INT16_MIN, None, <stdint.h>)
-SYMBOL(INT32_MAX, None, <stdint.h>)
-SYMBOL(INT32_MIN, None, <stdint.h>)
-SYMBOL(INT64_MAX, None, <stdint.h>)
-SYMBOL(INT64_MIN, None, <stdint.h>)
-SYMBOL(INT8_MAX, None, <stdint.h>)
-SYMBOL(INT8_MIN, None, <stdint.h>)
-SYMBOL(INTMAX_MAX, None, <stdint.h>)
-SYMBOL(INTMAX_MIN, None, <stdint.h>)
-SYMBOL(INTPTR_MAX, None, <stdint.h>)
-SYMBOL(INTPTR_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST16_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST16_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST32_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST32_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST64_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST64_MIN, None, <stdint.h>)
-SYMBOL(INT_FAST8_MAX, None, <stdint.h>)
-SYMBOL(INT_FAST8_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST16_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST16_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST32_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST32_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST64_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST64_MIN, None, <stdint.h>)
-SYMBOL(INT_LEAST8_MAX, None, <stdint.h>)
-SYMBOL(INT_LEAST8_MIN, None, <stdint.h>)
-SYMBOL(INT_MAX, None, <limits.h>)
-SYMBOL(INT_MIN, None, <limits.h>)
-SYMBOL(LC_ALL, None, <locale.h>)
-SYMBOL(LC_COLLATE, None, <locale.h>)
-SYMBOL(LC_CTYPE, None, <locale.h>)
-SYMBOL(LC_MONETARY, None, <locale.h>)
-SYMBOL(LC_NUMERIC, None, <locale.h>)
-SYMBOL(LC_TIME, None, <locale.h>)
-SYMBOL(LDBL_DECIMAL_DIG, None, <float.h>)
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-SYMBOL(LDBL_MAX_10_EXP, None, <float.h>)
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-SYMBOL(LDBL_TRUE_MIN, None, <float.h>)
-SYMBOL(LLONG_MAX, None, <limits.h>)
-SYMBOL(LLONG_MIN, None, <limits.h>)
-SYMBOL(LONG_MAX, None, <limits.h>)
-SYMBOL(LONG_MIN, None, <limits.h>)
-SYMBOL(L_tmpnam, None, <stdio.h>)
-SYMBOL(L_tmpnam_s, None, <stdio.h>)
-SYMBOL(MATH_ERREXCEPT, None, <math.h>)
-SYMBOL(MATH_ERRNO, None, <math.h>)
-SYMBOL(MB_CUR_MAX, None, <stdlib.h>)
-SYMBOL(MB_LEN_MAX, None, <limits.h>)
-SYMBOL(NAN, None, <math.h>)
-SYMBOL(ONCE_FLAG_INIT, None, <threads.h>)
-SYMBOL(PTRDIFF_MAX, None, <stdint.h>)
-SYMBOL(PTRDIFF_MIN, None, <stdint.h>)
-SYMBOL(RAND_MAX, None, <stdlib.h>)
-SYMBOL(RSIZE_MAX, None, <stdint.h>)
-SYMBOL(SCHAR_MAX, None, <limits.h>)
-SYMBOL(SCHAR_MIN, None, <limits.h>)
-SYMBOL(SEEK_CUR, None, <stdio.h>)
-SYMBOL(SEEK_END, None, <stdio.h>)
-SYMBOL(SEEK_SET, None, <stdio.h>)
-SYMBOL(SHRT_MAX, None, <limits.h>)
-SYMBOL(SHRT_MIN, None, <limits.h>)
-SYMBOL(SIGABRT, None, <signal.h>)
-SYMBOL(SIGFPE, None, <signal.h>)
-SYMBOL(SIGILL, None, <signal.h>)
-SYMBOL(SIGINT, None, <signal.h>)
-SYMBOL(SIGSEGV, None, <signal.h>)
-SYMBOL(SIGTERM, None, <signal.h>)
-SYMBOL(SIG_ATOMIC_MAX, None, <stdint.h>)
-SYMBOL(SIG_ATOMIC_MIN, None, <stdint.h>)
-SYMBOL(SIG_DFL, None, <signal.h>)
-SYMBOL(SIG_ERR, None, <signal.h>)
-SYMBOL(SIG_IGN, None, <signal.h>)
-SYMBOL(SIZE_MAX, None, <stdint.h>)
-SYMBOL(TIME_UTC, None, <time.h>)
-SYMBOL(TMP_MAX, None, <stdio.h>)
-SYMBOL(TMP_MAX_S, None, <stdio.h>)
-SYMBOL(TSS_DTOR_ITERATIONS, None, <threads.h>)
-SYMBOL(UCHAR_MAX, None, <limits.h>)
-SYMBOL(UINT16_MAX, None, <stdint.h>)
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-SYMBOL(UINT64_MAX, None, <stdint.h>)
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-SYMBOL(UINTPTR_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST16_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST32_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST64_MAX, None, <stdint.h>)
-SYMBOL(UINT_FAST8_MAX, None, <stdint.h>)
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-SYMBOL(UINT_LEAST32_MAX, None, <stdint.h>)
-SYMBOL(UINT_LEAST64_MAX, None, <stdint.h>)
-SYMBOL(UINT_LEAST8_MAX, None, <stdint.h>)
-SYMBOL(UINT_MAX, None, <limits.h>)
-SYMBOL(ULLONG_MAX, None, <limits.h>)
-SYMBOL(ULONG_MAX, None, <limits.h>)
-SYMBOL(USHRT_MAX, None, <limits.h>)
-SYMBOL(WCHAR_MAX, None, <wchar.h>)
-SYMBOL(WCHAR_MIN, None, <wchar.h>)
-SYMBOL(WEOF, None, <wchar.h>)
-SYMBOL(WINT_MAX, None, <stdint.h>)
-SYMBOL(WINT_MIN, None, <stdint.h>)
-SYMBOL(_Complex_I, None, <complex.h>)
-SYMBOL(_IOFBF, None, <stdio.h>)
-SYMBOL(_IOLBF, None, <stdio.h>)
-SYMBOL(_IONBF, None, <stdio.h>)
-SYMBOL(_Imaginary_I, None, <complex.h>)
-SYMBOL(__alignas_is_defined, None, <stdalign.h>)
-SYMBOL(__alignof_is_defined, None, <stdalign.h>)
-SYMBOL(abort_handler_s, None, <stdlib.h>)
+SYMBOL_VERSION(_Exit, None, <stdlib.h>, c99)
+SYMBOL(abort, None, <stdlib.h>)
+SYMBOL_VERSION(abort_handler_s, None, <stdlib.h>, c11)
 SYMBOL(abs, None, <stdlib.h>)
 SYMBOL(acos, None, <math.h>)
-SYMBOL(acosf, None, <math.h>)
-SYMBOL(acosh, None, <math.h>)
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-SYMBOL(alignas, None, <stdalign.h>)
-SYMBOL(aligned_alloc, None, <stdlib.h>)
-SYMBOL(alignof, None, <stdalign.h>)
-SYMBOL(and, None, <iso646.h>)
-SYMBOL(and_eq, None, <iso646.h>)
+SYMBOL_VERSION(acosf, None, <math.h>, c99)
+SYMBOL_VERSION(acosh, None, <math.h>, c99)
+SYMBOL_VERSION(acoshf, None, <math.h>, c99)
+SYMBOL_VERSION(acoshl, None, <math.h>, c99)
+SYMBOL_VERSION(acosl, None, <math.h>, c99)
+SYMBOL_VERSION(aligned_alloc, None, <stdlib.h>, c11)
 SYMBOL(asctime, None, <time.h>)
-SYMBOL(asctime_s, None, <time.h>)
+SYMBOL_VERSION(asctime_s, None, <time.h>, c11)
 SYMBOL(asin, None, <math.h>)
-SYMBOL(asinf, None, <math.h>)
-SYMBOL(asinh, None, <math.h>)
-SYMBOL(asinhf, None, <math.h>)
-SYMBOL(asinhl, None, <math.h>)
-SYMBOL(asinl, None, <math.h>)
-SYMBOL(assert, None, <assert.h>)
-SYMBOL(at_quick_exit, None, <stdlib.h>)
+SYMBOL_VERSION(asinf, None, <math.h>, c99)
+SYMBOL_VERSION(asinh, None, <math.h>, c99)
+SYMBOL_VERSION(asinhf, None, <math.h>, c99)
+SYMBOL_VERSION(asinhl, None, <math.h>, c99)
+SYMBOL_VERSION(asinl, None, <math.h>, c99)
+SYMBOL_VERSION(at_quick_exit, None, <stdlib.h>, c11)
 SYMBOL(atan, None, <math.h>)
 SYMBOL(atan2, None, <math.h>)
-SYMBOL(atan2f, None, <math.h>)
-SYMBOL(atan2l, None, <math.h>)
-SYMBOL(atanf, None, <math.h>)
-SYMBOL(atanh, None, <math.h>)
-SYMBOL(atanhf, None, <math.h>)
-SYMBOL(atanhl, None, <math.h>)
-SYMBOL(atanl, None, <math.h>)
+SYMBOL_VERSION(atan2f, None, <math.h>, c99)
+SYMBOL_VERSION(atan2l, None, <math.h>, c99)
+SYMBOL_VERSION(atanf, None, <math.h>, c99)
+SYMBOL_VERSION(atanh, None, <math.h>, c99)
+SYMBOL_VERSION(atanhf, None, <math.h>, c99)
+SYMBOL_VERSION(atanhl, None, <math.h>, c99)
+SYMBOL_VERSION(atanl, None, <math.h>, c99)
 SYMBOL(atexit, None, <stdlib.h>)
 SYMBOL(atof, None, <stdlib.h>)
 SYMBOL(atoi, None, <stdlib.h>)
 SYMBOL(atol, None, <stdlib.h>)
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-SYMBOL(atomic_char, None, <stdatomic.h>)
-SYMBOL(atomic_char16_t, None, <stdatomic.h>)
-SYMBOL(atomic_char32_t, None, <stdatomic.h>)
+SYMBOL_VERSION(atoll,...
[truncated]

github-actions · 2025-06-29T02:24:47Z

✅ With the latest revision this PR passed the C/C++ code formatter.

Clang now tries to suggest and hint standard library include file by emitting the following. ``` 4 | std::unordered_map<std::string, std::string> map; | ^~~~~~~~~~~~~ main.cpp:4:10: note: maybe try to include <unordered_map>; 'std::unordered_map' is defined in <unordered_map> main.cpp:4:10: note: 'std::unordered_map' is a c++11 feature main.cpp:4:42: note: maybe try to include <string>; 'std::string' is defined in <string> ``` This works for both C and C++. fixes llvm#120388

erichkeane

I'm not really a fan of how we're doing this. This should only be caused by a failed lookup. This also seems about 2x as complicated as it needs to be. I like the idea ehre, but not at this level of complexity.

@AaronBallman perhaps has a better idea of extended tooling.

erichkeane · 2025-07-01T13:11:16Z

clang/docs/ReleaseNotes.rst

@@ -478,6 +478,7 @@ Improvements to Clang's diagnostics
  diagnostics. This fixes a bunch of `bool` being printed as `_Bool`, and also
  a bunch of HLSL types being printed as their C++ equivalents.
 - Clang now consistently quotes expressions in diagnostics.
+- Clang now suggest standard library include path and its associated C++ or C language version.


Suggested change

- Clang now suggest standard library include path and its associated C++ or C language version.

- Clang now suggests including standard library headers when encountering standard types.

erichkeane · 2025-07-01T13:12:30Z

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -5990,6 +5990,10 @@ def err_template_expansion_into_fixed_list : Error<
  "template|concept}0">;
 def note_parameter_type : Note<
  "parameter of type %0 is declared here">;
+def note_standard_lib_include_suggestion : Note<
+  "maybe try to include %0; '%1' is defined in %0">;


Suggested change

"maybe try to include %0; '%1' is defined in %0">;

"'%1' is defined in %0; did you mean to include it?">;

erichkeane · 2025-07-01T13:14:44Z

clang/include/clang/Tooling/Inclusions/StandardLibrary.h

@@ -29,6 +29,27 @@ class NamespaceDecl;
 class DeclContext;
 namespace tooling {
 namespace stdlib {
+enum Version {


We already have enums for standards versions elsewhere, I don't want us maintaining ANOTHER one. So I'm against this enum entirely.

erichkeane · 2025-07-01T13:15:26Z

clang/include/clang/Basic/DiagnosticSemaKinds.td

+def note_standard_lib_include_suggestion : Note<
+  "maybe try to include %0; '%1' is defined in %0">;
+def note_standard_lib_version : Note<
+  "'%0' is a %1 feature">;


We should probably be doing something more like:
"'%0::%1' is a %enum_select..." for this.

erichkeane · 2025-07-01T13:15:31Z

clang/include/clang/Sema/Sema.h

+  // \param SymbolName the symbol name like 'cout'
+  // \param SourceLocation the location of the note being emitted
+  // \param Namespace the namespace that must end with ::, so like 'std::'
+  void NoteStandardIncludes(StringRef SymbolName, SourceLocation IILoc,


I'm not really a fan of this interface. Unless it is particularly easy, we shouldn't be forcing the inclusion of the '::' in this interface.

FYI, the interface in clangToolingInclusionsStdlib requires the inclusion of ::, so Namesace+SymbolName gives you the full name. I am fine with removing the inclusion of :: at the end.

erichkeane · 2025-07-01T13:15:48Z

clang/lib/Parse/ParseExprCXX.cpp

+  // If `FailedNestedNameBuilding` is true, attempt to suggest the standard
+  // include file corresponding to the current `FullNamespace` and symbol.
+  std::string FullNamespace = "";
+  bool FailedNesatedNameBuilding = false;


Suggested change

bool FailedNesatedNameBuilding = false;

bool FailedNestedNameBuilding = false;

erichkeane · 2025-07-01T13:16:15Z

clang/lib/Parse/ParseExprCXX.cpp

@@ -454,6 +459,9 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
      // We have an identifier followed by a '::'. Lookup this name
      // as the name in a nested-name-specifier.
      Token Identifier = Tok;
+      FullNamespace += Identifier.getIdentifierInfo()->getName();
+      FullNamespace += "::";


As this is extra work, just make it a part of the printing, not here. Better yet, instead of storing FullNameSpace, just store the IdentifierInfo list.

erichkeane · 2025-07-01T13:17:38Z

clang/lib/Parse/ParseExprCXX.cpp

@@ -465,6 +473,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
      if (Actions.ActOnCXXNestedNameSpecifier(
              getCurScope(), IdInfo, EnteringContext, SS, CorrectionFlagPtr,
              OnlyNamespace)) {
+        FailedNesatedNameBuilding = true;


I think we ONLY are going to want to suggest things of the pattern NS::TypeName. So ensuring we have hte 'full name' isn't really necessary. I think we can just store the namespace and identifier.

erichkeane · 2025-07-01T13:18:23Z

clang/lib/Parse/ParseExprCXX.cpp

@@ -554,6 +563,11 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
    break;
  }

+  if (FailedNesatedNameBuilding && Tok.getKind() == tok::identifier) {


Parser isn't really the right place to do this. This is very much a 'sema' diagnostic/suggestion. This should happen not here, but on failed lookup.

I completed agree with you for the fact that this is really ugly code here.

The problem I am trying to solve here is when there is no declaration for the std namespace.

// this is the entire file void some_func(){ std::cout << "some func has been called" << std::endl; }

Here building the nested name will fail because there is no namespace std being defined anywhere, so a name lookup for cout is never performed (as far as I can tell, there could be something I am missing here). I am not sure if there is an easy fix to that in Sema level.

However, something like the following would work cause the suggestion to trigger. It is okay if I revert this file?

namespace std {}; // this is the entire file void some_func(){ std::cout << "some func has been called" << std::endl; }

erichkeane · 2025-07-01T13:21:21Z

clang/lib/Sema/SemaDecl.cpp

+          << HeaderName << (Namespace + SymbolName).str();
+
+      // Noting the C/C++ version as well
+      if (StdSym->version() != tooling::stdlib::Unknown) {


Version stuff we should be handling via our diagnostic, not doing it this way.

llvmbot added clang Clang issues not falling into any other category clang:frontend Language frontend issues, e.g. anything involving "Sema" clang:modules C++20 modules and Clang Header Modules labels Jun 28, 2025

Mr-Anyone marked this pull request as draft June 28, 2025 16:50

Mr-Anyone force-pushed the include_suggestions_pr branch from 734e586 to f671c52 Compare June 29, 2025 02:22

Mr-Anyone force-pushed the include_suggestions_pr branch from f671c52 to 1a01836 Compare June 29, 2025 02:28

Mr-Anyone marked this pull request as ready for review June 29, 2025 03:32

Mr-Anyone force-pushed the include_suggestions_pr branch from 1a01836 to a2b2210 Compare June 30, 2025 05:19

shafik requested review from zyn0217 and erichkeane June 30, 2025 22:17

erichkeane reviewed Jul 1, 2025

View reviewed changes

	- Clang now suggest standard library include path and its associated C++ or C language version.
	- Clang now suggests including standard library headers when encountering standard types.

	"maybe try to include %0; '%1' is defined in %0">;
	"'%1' is defined in %0; did you mean to include it?">;

	bool FailedNesatedNameBuilding = false;
	bool FailedNestedNameBuilding = false;

[clang][Sema] Suggest/Hint Standard Library Include File #146227

Are you sure you want to change the base?

[clang][Sema] Suggest/Hint Standard Library Include File #146227

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Mr-Anyone commented Jun 28, 2025

Uh oh!

llvmbot commented Jun 28, 2025

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llvmbot commented Jun 28, 2025

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github-actions bot commented Jun 29, 2025 •

edited

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