[libc-commits] [libc] [libc][RFC] add support for function level attributes (PR #79891)

Schrodinger ZHU Yifan via libc-commits libc-commits at lists.llvm.org
Wed Jan 31 06:27:54 PST 2024


https://github.com/SchrodingerZhu updated https://github.com/llvm/llvm-project/pull/79891

>From 0166fde93dc1165fd0743f85a5262d5762b2c0e9 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Mon, 29 Jan 2024 14:21:25 -0500
Subject: [PATCH 1/4] [libc][RFC] add support for function level attributes

---
 libc/spec/spec.td                      | 21 ++++++-
 libc/utils/HdrGen/PublicAPICommand.cpp | 77 ++++++++++++++++++++++++--
 libc/utils/HdrGen/PublicAPICommand.h   |  2 +
 3 files changed, 95 insertions(+), 5 deletions(-)

diff --git a/libc/spec/spec.td b/libc/spec/spec.td
index 16abf97bf0b1c..16019fbf4fd3f 100644
--- a/libc/spec/spec.td
+++ b/libc/spec/spec.td
@@ -170,10 +170,29 @@ class ArgSpec<Type type, list<Annotation> annotations = [], string name = ""> {
   string Name = name;
 }
 
-class FunctionSpec<string name, RetValSpec return, list<ArgSpec> args> {
+class FunctionAttr {}
+class GnuFunctionAttr<string attr> : FunctionAttr {
+  string Attr = attr;
+  string Style = "gnu";
+}
+class C23FunctionAttr<string attr, string namespace> : FunctionAttr {
+  string Attr = attr;
+  string Namespace = namespace;
+  string Style = "c23";
+}
+class DeclspecFunctionAttr<string attr> : FunctionAttr {
+  string Attr = attr;
+  string Style = "declspec";
+}
+class FunctionAttrSpec<list<FunctionAttr> instances> {
+  list<FunctionAttr> Instances = instances;
+}
+
+class FunctionSpec<string name, RetValSpec return, list<ArgSpec> args, list<FunctionAttrSpec> attrs = []> {
   string Name = name;
   RetValSpec Return = return;
   list<ArgSpec> Args = args;
+  list<FunctionAttrSpec> Attributes = attrs;
 }
 
 class ObjectSpec<string name, string type> {
diff --git a/libc/utils/HdrGen/PublicAPICommand.cpp b/libc/utils/HdrGen/PublicAPICommand.cpp
index b1c7a072658ff..26eb14c758920 100644
--- a/libc/utils/HdrGen/PublicAPICommand.cpp
+++ b/libc/utils/HdrGen/PublicAPICommand.cpp
@@ -15,6 +15,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/TableGen/Record.h"
+#include <llvm/ADT/STLExtras.h>
 
 // Text blocks for macro definitions and type decls can be indented to
 // suit the surrounding tablegen listing. We need to dedent such blocks
@@ -49,7 +50,7 @@ namespace llvm_libc {
 
 void writeAPIFromIndex(APIIndexer &G,
                        std::vector<std::string> EntrypointNameList,
-                       llvm::raw_ostream &OS) {
+                       llvm::raw_ostream &OS, AttributeStyle PreferedStyle) {
   for (auto &Pair : G.MacroDefsMap) {
     const std::string &Name = Pair.first;
     if (G.MacroSpecMap.find(Name) == G.MacroSpecMap.end())
@@ -102,6 +103,62 @@ void writeAPIFromIndex(APIIndexer &G,
     llvm::Record *RetValSpec = FunctionSpec->getValueAsDef("Return");
     llvm::Record *ReturnType = RetValSpec->getValueAsDef("ReturnType");
 
+    auto GetStyle = [](llvm::Record *Instance) {
+      auto Style = Instance->getValueAsString("Style");
+      if (Style == "gnu")
+        return AttributeStyle::Gnu;
+      if (Style == "c23")
+        return AttributeStyle::C23;
+      if (Style == "declspec")
+        return AttributeStyle::Declspec;
+      return AttributeStyle::None;
+    };
+
+    if (PreferedStyle != AttributeStyle::None) {
+      auto Attributes = FunctionSpec->getValueAsListOfDefs("Attributes");
+      llvm::SmallVector<llvm::Record *> Attrs;
+      for (auto *Attr : Attributes) {
+        auto Instances = Attr->getValueAsListOfDefs("Instances");
+        for (auto *Instance : Instances) {
+          if (GetStyle(Instance) == PreferedStyle) {
+            Attrs.push_back(Instance);
+          }
+        }
+      }
+
+      if (Attrs.size() != 0) {
+        if (PreferedStyle == AttributeStyle::Gnu) {
+          OS << "__attribute__((";
+          llvm::interleaveComma(Attrs, OS, [&](llvm::Record *Instance) {
+            OS << Instance->getValueAsString("Attr");
+          });
+          OS << ")) ";
+        }
+
+        if (PreferedStyle == AttributeStyle::C23) {
+          OS << "__attribute__((";
+          llvm::interleaveComma(Attrs, OS, [&](llvm::Record *Instance) {
+            auto Namespace = Instance->getValueAsString("Namespace");
+            if (Namespace != "")
+              OS << Namespace << "::";
+            OS << Instance->getValueAsString("Attr");
+          });
+          OS << ")) ";
+        }
+
+        if (PreferedStyle == AttributeStyle::Declspec) {
+          OS << "__declspec(";
+          llvm::interleave(
+              Attrs.begin(), Attrs.end(),
+              [&](llvm::Record *Instance) {
+                OS << Instance->getValueAsString("Attr");
+              },
+              [&]() { OS << ' '; });
+          OS << ") ";
+        }
+      }
+    }
+
     OS << G.getTypeAsString(ReturnType) << " " << Name << "(";
 
     auto ArgsList = FunctionSpec->getValueAsListOfDefs("Args");
@@ -134,12 +191,24 @@ void PublicAPICommand::run(llvm::raw_ostream &OS, const ArgVector &Args,
                            llvm::StringRef StdHeader,
                            llvm::RecordKeeper &Records,
                            const Command::ErrorReporter &Reporter) const {
-  if (Args.size() != 0) {
-    Reporter.printFatalError("public_api command does not take any arguments.");
+  if (Args.size() > 1) {
+    Reporter.printFatalError(
+        "public_api command does not take more than one arguments.");
+  }
+
+  AttributeStyle PreferedStyle = AttributeStyle::Gnu;
+
+  for (auto &arg : Args) {
+    if (arg == "prefer-c23-attributes") {
+      PreferedStyle = AttributeStyle::C23;
+    }
+    if (arg == "prefer-no-attributes") {
+      PreferedStyle = AttributeStyle::None;
+    }
   }
 
   APIIndexer G(StdHeader, Records);
-  writeAPIFromIndex(G, EntrypointNameList, OS);
+  writeAPIFromIndex(G, EntrypointNameList, OS, PreferedStyle);
 }
 
 } // namespace llvm_libc
diff --git a/libc/utils/HdrGen/PublicAPICommand.h b/libc/utils/HdrGen/PublicAPICommand.h
index fb0a7a81cf277..035e1c71f4f12 100644
--- a/libc/utils/HdrGen/PublicAPICommand.h
+++ b/libc/utils/HdrGen/PublicAPICommand.h
@@ -25,6 +25,8 @@ class RecordKeeper;
 
 namespace llvm_libc {
 
+enum class AttributeStyle { None, Gnu, C23, Declspec };
+
 class PublicAPICommand : public Command {
 private:
   const std::vector<std::string> &EntrypointNameList;

>From 9eef29083ad0ffcce341d1c9af47fad8909102ec Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Mon, 29 Jan 2024 15:05:04 -0500
Subject: [PATCH 2/4] [libc][RFC] add support for function level attributes

---
 libc/spec/spec.td                      |   7 +-
 libc/spec/stdc.td                      |   7 +-
 libc/utils/HdrGen/PublicAPICommand.cpp | 152 +++++++++++++------------
 libc/utils/HdrGen/PublicAPICommand.h   |   2 +-
 4 files changed, 92 insertions(+), 76 deletions(-)

diff --git a/libc/spec/spec.td b/libc/spec/spec.td
index 16019fbf4fd3f..8813f69ac3aa7 100644
--- a/libc/spec/spec.td
+++ b/libc/spec/spec.td
@@ -175,17 +175,18 @@ class GnuFunctionAttr<string attr> : FunctionAttr {
   string Attr = attr;
   string Style = "gnu";
 }
-class C23FunctionAttr<string attr, string namespace> : FunctionAttr {
+class Cxx11FunctionAttr<string attr, string namespace> : FunctionAttr {
   string Attr = attr;
   string Namespace = namespace;
-  string Style = "c23";
+  string Style = "cxx11";
 }
 class DeclspecFunctionAttr<string attr> : FunctionAttr {
   string Attr = attr;
   string Style = "declspec";
 }
-class FunctionAttrSpec<list<FunctionAttr> instances> {
+class FunctionAttrSpec<string macro, list<FunctionAttr> instances> {
   list<FunctionAttr> Instances = instances;
+  string Macro = macro;
 }
 
 class FunctionSpec<string name, RetValSpec return, list<ArgSpec> args, list<FunctionAttrSpec> attrs = []> {
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
index b21f620d0766a..1951638aa55dd 100644
--- a/libc/spec/stdc.td
+++ b/libc/spec/stdc.td
@@ -26,6 +26,11 @@ def StdC : StandardSpec<"stdc"> {
       []
   >;
 
+  FunctionAttrSpec ConstAttr = FunctionAttrSpec<"__LIBC_CONST_ATTR", [
+    Cxx11FunctionAttr<"const", "gnu">,
+    GnuFunctionAttr<"const">,
+  ]>;
+
   HeaderSpec CType = HeaderSpec<
       "ctype.h",
       [], // Macros
@@ -364,7 +369,7 @@ def StdC : StandardSpec<"stdc"> {
           FunctionSpec<"ceilf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
           FunctionSpec<"ceill", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>]>,
 
-          FunctionSpec<"fabs", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
+          FunctionSpec<"fabs", RetValSpec<DoubleType>, [ArgSpec<DoubleType>], [ConstAttr]>,
           FunctionSpec<"fabsf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
           FunctionSpec<"fabsl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>]>,
           FunctionSpec<"fabsf128", RetValSpec<Float128Type>, [ArgSpec<Float128Type>]>,
diff --git a/libc/utils/HdrGen/PublicAPICommand.cpp b/libc/utils/HdrGen/PublicAPICommand.cpp
index 26eb14c758920..d24637db0f788 100644
--- a/libc/utils/HdrGen/PublicAPICommand.cpp
+++ b/libc/utils/HdrGen/PublicAPICommand.cpp
@@ -15,6 +15,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/TableGen/Record.h"
+#include <algorithm>
 #include <llvm/ADT/STLExtras.h>
 
 // Text blocks for macro definitions and type decls can be indented to
@@ -50,7 +51,7 @@ namespace llvm_libc {
 
 void writeAPIFromIndex(APIIndexer &G,
                        std::vector<std::string> EntrypointNameList,
-                       llvm::raw_ostream &OS, AttributeStyle PreferedStyle) {
+                       llvm::raw_ostream &OS) {
   for (auto &Pair : G.MacroDefsMap) {
     const std::string &Name = Pair.first;
     if (G.MacroSpecMap.find(Name) == G.MacroSpecMap.end())
@@ -88,6 +89,71 @@ void writeAPIFromIndex(APIIndexer &G,
   if (G.Enumerations.size() != 0)
     OS << "};\n\n";
 
+  // declare macros for attributes
+  llvm::DenseMap<llvm::StringRef, llvm::Record *> MacroAttr;
+  for (auto &Name : EntrypointNameList) {
+    if (G.FunctionSpecMap.find(Name) == G.FunctionSpecMap.end()) {
+      continue;
+    }
+    llvm::Record *FunctionSpec = G.FunctionSpecMap[Name];
+    auto Attributes = FunctionSpec->getValueAsListOfDefs("Attributes");
+    for (auto *Attr : Attributes) {
+      MacroAttr[Attr->getValueAsString("Macro")] = Attr;
+    }
+  }
+
+  auto GetStyle = [](llvm::Record *Instance) {
+    auto Style = Instance->getValueAsString("Style");
+    if (Style == "cxx11")
+      return AttributeStyle::Cxx11;
+    if (Style == "gnu")
+      return AttributeStyle::Gnu;
+    return AttributeStyle::Declspec;
+  };
+
+  for (auto &[Macro, Attr] : MacroAttr) {
+    auto Instances = Attr->getValueAsListOfDefs("Instances");
+    llvm::SmallVector<std::pair<AttributeStyle, llvm::Record *>> Styles;
+    std::transform(Instances.begin(), Instances.end(),
+                   std::back_inserter(Styles),
+                   [&](llvm::Record *Instance)
+                       -> std::pair<AttributeStyle, llvm::Record *> {
+                     auto Style = GetStyle(Instance);
+                     return {Style, Instance};
+                   });
+    // Effectively sort on the first field
+    std::sort(Styles.begin(), Styles.end());
+    for (auto &[Style, Instance] : Styles) {
+      if (Style == AttributeStyle::Cxx11) {
+        OS << "#if !defined(" << Macro << ") && defined(__cplusplus)\n";
+        OS << "#define " << Macro << " [[";
+        auto Namespace = Instance->getValueAsString("Namespace");
+        if (Namespace != "")
+          OS << Namespace << "::";
+        OS << Instance->getValueAsString("Attr") << "]]\n";
+        OS << "#endif\n";
+      }
+      if (Style == AttributeStyle::Gnu) {
+        OS << "#if !defined(" << Macro << ") && defined(__GNUC__)\n";
+        OS << "#define " << Macro << " __attribute__((";
+        OS << Instance->getValueAsString("Attr") << "))\n";
+        OS << "#endif\n";
+      }
+      if (Style == AttributeStyle::Declspec) {
+        OS << "#if !defined(" << Macro << ") && defined(_MSC_VER)\n";
+        OS << "#define " << Macro << " __declspec(";
+        OS << Instance->getValueAsString("Attr") << ")\n";
+        OS << "#endif\n";
+      }
+    }
+    OS << "#if !defined(" << Macro << ")\n";
+    OS << "#define " << Macro << '\n';
+    OS << "#endif\n";
+  }
+
+  if (!MacroAttr.empty())
+    OS << '\n';
+
   OS << "__BEGIN_C_DECLS\n\n";
   for (auto &Name : EntrypointNameList) {
     if (G.FunctionSpecMap.find(Name) == G.FunctionSpecMap.end()) {
@@ -103,61 +169,13 @@ void writeAPIFromIndex(APIIndexer &G,
     llvm::Record *RetValSpec = FunctionSpec->getValueAsDef("Return");
     llvm::Record *ReturnType = RetValSpec->getValueAsDef("ReturnType");
 
-    auto GetStyle = [](llvm::Record *Instance) {
-      auto Style = Instance->getValueAsString("Style");
-      if (Style == "gnu")
-        return AttributeStyle::Gnu;
-      if (Style == "c23")
-        return AttributeStyle::C23;
-      if (Style == "declspec")
-        return AttributeStyle::Declspec;
-      return AttributeStyle::None;
-    };
-
-    if (PreferedStyle != AttributeStyle::None) {
-      auto Attributes = FunctionSpec->getValueAsListOfDefs("Attributes");
-      llvm::SmallVector<llvm::Record *> Attrs;
-      for (auto *Attr : Attributes) {
-        auto Instances = Attr->getValueAsListOfDefs("Instances");
-        for (auto *Instance : Instances) {
-          if (GetStyle(Instance) == PreferedStyle) {
-            Attrs.push_back(Instance);
-          }
-        }
-      }
-
-      if (Attrs.size() != 0) {
-        if (PreferedStyle == AttributeStyle::Gnu) {
-          OS << "__attribute__((";
-          llvm::interleaveComma(Attrs, OS, [&](llvm::Record *Instance) {
-            OS << Instance->getValueAsString("Attr");
-          });
-          OS << ")) ";
-        }
-
-        if (PreferedStyle == AttributeStyle::C23) {
-          OS << "__attribute__((";
-          llvm::interleaveComma(Attrs, OS, [&](llvm::Record *Instance) {
-            auto Namespace = Instance->getValueAsString("Namespace");
-            if (Namespace != "")
-              OS << Namespace << "::";
-            OS << Instance->getValueAsString("Attr");
-          });
-          OS << ")) ";
-        }
-
-        if (PreferedStyle == AttributeStyle::Declspec) {
-          OS << "__declspec(";
-          llvm::interleave(
-              Attrs.begin(), Attrs.end(),
-              [&](llvm::Record *Instance) {
-                OS << Instance->getValueAsString("Attr");
-              },
-              [&]() { OS << ' '; });
-          OS << ") ";
-        }
-      }
-    }
+    auto Attributes = FunctionSpec->getValueAsListOfDefs("Attributes");
+    llvm::interleave(
+        Attributes.begin(), Attributes.end(),
+        [&](llvm::Record *Attr) { OS << Attr->getValueAsString("Macro"); },
+        [&]() { OS << ' '; });
+    if (!Attributes.empty())
+      OS << ' ';
 
     OS << G.getTypeAsString(ReturnType) << " " << Name << "(";
 
@@ -181,6 +199,10 @@ void writeAPIFromIndex(APIIndexer &G,
     OS << "extern " << Type << " " << Name << ";\n";
   }
   OS << "__END_C_DECLS\n";
+
+  // undef the macros
+  for (auto &[Macro, Attr] : MacroAttr)
+    OS << "\n#undef " << Macro << '\n';
 }
 
 void writePublicAPI(llvm::raw_ostream &OS, llvm::RecordKeeper &Records) {}
@@ -191,24 +213,12 @@ void PublicAPICommand::run(llvm::raw_ostream &OS, const ArgVector &Args,
                            llvm::StringRef StdHeader,
                            llvm::RecordKeeper &Records,
                            const Command::ErrorReporter &Reporter) const {
-  if (Args.size() > 1) {
-    Reporter.printFatalError(
-        "public_api command does not take more than one arguments.");
-  }
-
-  AttributeStyle PreferedStyle = AttributeStyle::Gnu;
-
-  for (auto &arg : Args) {
-    if (arg == "prefer-c23-attributes") {
-      PreferedStyle = AttributeStyle::C23;
-    }
-    if (arg == "prefer-no-attributes") {
-      PreferedStyle = AttributeStyle::None;
-    }
+  if (Args.size() != 0) {
+    Reporter.printFatalError("public_api command does not take any arguments.");
   }
 
   APIIndexer G(StdHeader, Records);
-  writeAPIFromIndex(G, EntrypointNameList, OS, PreferedStyle);
+  writeAPIFromIndex(G, EntrypointNameList, OS);
 }
 
 } // namespace llvm_libc
diff --git a/libc/utils/HdrGen/PublicAPICommand.h b/libc/utils/HdrGen/PublicAPICommand.h
index 035e1c71f4f12..72401cfe068e3 100644
--- a/libc/utils/HdrGen/PublicAPICommand.h
+++ b/libc/utils/HdrGen/PublicAPICommand.h
@@ -25,7 +25,7 @@ class RecordKeeper;
 
 namespace llvm_libc {
 
-enum class AttributeStyle { None, Gnu, C23, Declspec };
+enum class AttributeStyle { Cxx11 = 0, Gnu = 1, Declspec = 2 };
 
 class PublicAPICommand : public Command {
 private:

>From 126630ef7d1871fd748b12d07e0ccaddd926b1fb Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 30 Jan 2024 09:38:49 -0500
Subject: [PATCH 3/4] add checks for namespaces

---
 libc/utils/HdrGen/PublicAPICommand.cpp | 33 ++++++++++++++++++++++----
 libc/utils/HdrGen/PublicAPICommand.h   |  1 +
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/libc/utils/HdrGen/PublicAPICommand.cpp b/libc/utils/HdrGen/PublicAPICommand.cpp
index d24637db0f788..8ddb2ea5eaf90 100644
--- a/libc/utils/HdrGen/PublicAPICommand.cpp
+++ b/libc/utils/HdrGen/PublicAPICommand.cpp
@@ -111,6 +111,17 @@ void writeAPIFromIndex(APIIndexer &G,
     return AttributeStyle::Declspec;
   };
 
+  auto GetNamespace = [](llvm::Record *Instance) {
+    auto Namespace = Instance->getValueAsString("Namespace");
+    // Empty namespace is likely to be most standard-compliant.
+    if (Namespace == "")
+      return AttributeNamespace::None;
+    // Dispatch clang version before gnu version.
+    if (Namespace == "clang")
+      return AttributeNamespace::Clang;
+    return AttributeNamespace::Gnu;
+  };
+
   for (auto &[Macro, Attr] : MacroAttr) {
     auto Instances = Attr->getValueAsListOfDefs("Instances");
     llvm::SmallVector<std::pair<AttributeStyle, llvm::Record *>> Styles;
@@ -122,14 +133,26 @@ void writeAPIFromIndex(APIIndexer &G,
                      return {Style, Instance};
                    });
     // Effectively sort on the first field
-    std::sort(Styles.begin(), Styles.end());
+    std::sort(Styles.begin(), Styles.end(), [&](auto &a, auto &b) {
+      if (a.first == AttributeStyle::Cxx11 && b.first == AttributeStyle::Cxx11)
+        return GetNamespace(a.second) < GetNamespace(b.second);
+      return a.first < b.first;
+    });
     for (auto &[Style, Instance] : Styles) {
       if (Style == AttributeStyle::Cxx11) {
-        OS << "#if !defined(" << Macro << ") && defined(__cplusplus)\n";
+        OS << "#if !defined(" << Macro << ") && defined(__cplusplus)";
+        auto Namespace = GetNamespace(Instance);
+        if (Namespace == AttributeNamespace::Clang)
+          OS << " && defined(__clang__)\n";
+        else if (Namespace == AttributeNamespace::Gnu)
+          OS << " && defined(__GNUC__)\n";
+        else
+          OS << '\n';
         OS << "#define " << Macro << " [[";
-        auto Namespace = Instance->getValueAsString("Namespace");
-        if (Namespace != "")
-          OS << Namespace << "::";
+        if (Namespace == AttributeNamespace::Clang)
+          OS << "clang::";
+        else if (Namespace == AttributeNamespace::Gnu)
+          OS << "gnu::";
         OS << Instance->getValueAsString("Attr") << "]]\n";
         OS << "#endif\n";
       }
diff --git a/libc/utils/HdrGen/PublicAPICommand.h b/libc/utils/HdrGen/PublicAPICommand.h
index 72401cfe068e3..41aa53e51c326 100644
--- a/libc/utils/HdrGen/PublicAPICommand.h
+++ b/libc/utils/HdrGen/PublicAPICommand.h
@@ -26,6 +26,7 @@ class RecordKeeper;
 namespace llvm_libc {
 
 enum class AttributeStyle { Cxx11 = 0, Gnu = 1, Declspec = 2 };
+enum class AttributeNamespace { None = 0, Clang = 1, Gnu = 2 };
 
 class PublicAPICommand : public Command {
 private:

>From 79419bddeacc22d5e52b27eca8c38feb3028e6e7 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 30 Jan 2024 09:40:07 -0500
Subject: [PATCH 4/4] use empty() instead of literal

---
 libc/utils/HdrGen/PublicAPICommand.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libc/utils/HdrGen/PublicAPICommand.cpp b/libc/utils/HdrGen/PublicAPICommand.cpp
index 8ddb2ea5eaf90..799be24ee0d8c 100644
--- a/libc/utils/HdrGen/PublicAPICommand.cpp
+++ b/libc/utils/HdrGen/PublicAPICommand.cpp
@@ -114,7 +114,7 @@ void writeAPIFromIndex(APIIndexer &G,
   auto GetNamespace = [](llvm::Record *Instance) {
     auto Namespace = Instance->getValueAsString("Namespace");
     // Empty namespace is likely to be most standard-compliant.
-    if (Namespace == "")
+    if (Namespace.empty())
       return AttributeNamespace::None;
     // Dispatch clang version before gnu version.
     if (Namespace == "clang")



More information about the libc-commits mailing list