[clang-tidy] Update llvmlibc-implementation-in-namespace to new rules

[gchatelet]

This is the implementation of step 3 of
https://discourse.llvm.org/t/rfc-customizable-namespace-to-allow-testing-the-libc-when-the-system-libc-is-also-llvms-libc/73079.

[llvmbot]

@llvm/pr-subscribers-clang-tidy

Changes

This is the implementation of step 3 of https://discourse.llvm.org/t/rfc-customizable-namespace-to-allow-testing-the-libc-when-the-system-libc-is-also-llvms-libc/73079.

--
Full diff: https://github.com/llvm/llvm-project/pull/66504.diff

3 Files Affected:

• (modified) clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp (+13-8)
• (modified) clang-tools-extra/docs/clang-tidy/checks/llvmlibc/implementation-in-namespace.rst (+16-7)
• (modified) clang-tools-extra/test/clang-tidy/checkers/llvmlibc/implementation-in-namespace.cpp (+21-10)

diff --git a/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp
index d05310f09ef773a..69a385f5be9807f 100644
--- a/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvmlibc/ImplementationInNamespaceCheck.cpp
@@ -14,7 +14,9 @@ using namespace clang::ast_matchers;
 
 namespace clang::tidy::llvm_libc {
 
-const static StringRef RequiredNamespace = "__llvm_libc";
+const static StringRef RequiredNamespaceStart = "__llvm_libc";
+const static StringRef RequiredNamespaceMacroName = "LIBC_NAMESPACE";
+
 void ImplementationInNamespaceCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
       decl(hasParent(translationUnitDecl()), unless(linkageSpecDecl()))
@@ -29,16 +31,19 @@ void ImplementationInNamespaceCheck::check(
   if (!Result.SourceManager->isInMainFile(MatchedDecl->getLocation()))
     return;
 
-  if (const auto *NS = dyn_cast<NamespaceDecl>(MatchedDecl)) {
-    if (NS->getName() != RequiredNamespace) {
-      diag(NS->getLocation(), "'%0' needs to be the outermost namespace")
-          << RequiredNamespace;
-    }
+  if (auto *NS = dyn_cast<NamespaceDecl>(MatchedDecl)) {
+    if (!Result.SourceManager->isMacroBodyExpansion(NS->getLocation()))
+      diag(NS->getLocation(),
+           "the outermost namespace should be the '%0' macro")
+          << RequiredNamespaceMacroName;
+    else if (!NS->getName().starts_with(RequiredNamespaceStart))
+      diag(NS->getLocation(), "the outermost namespace should start with '%0'")
+          << RequiredNamespaceStart;
     return;
   }
   diag(MatchedDecl->getLocation(),
-       "declaration must be declared within the '%0' namespace")
-      << RequiredNamespace;
+       "declaration must be declared within a namespace starting with '%0'")
+      << RequiredNamespaceStart;
 }
 
 } // namespace clang::tidy::llvm_libc
diff --git a/clang-tools-extra/docs/clang-tidy/checks/llvmlibc/implementation-in-namespace.rst b/clang-tools-extra/docs/clang-tidy/checks/llvmlibc/implementation-in-namespace.rst
index 33d6dc8ff125c84..47ea2b866a93404 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/llvmlibc/implementation-in-namespace.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/llvmlibc/implementation-in-namespace.rst
@@ -8,21 +8,30 @@ correct namespace.
 
 .. code-block:: c++
 
-    // Correct: implementation inside the correct namespace.
-    namespace __llvm_libc {
+    // Implementation inside the LIBC_NAMESPACE namespace.
+    // Correct if:
+    // - LIBC_NAMESPACE is a macro
+    // - LIBC_NAMESPACE expansion starts with `__llvm_libc`
+    namespace LIBC_NAMESPACE {
         void LLVM_LIBC_ENTRYPOINT(strcpy)(char *dest, const char *src) {}
-        // Namespaces within __llvm_libc namespace are allowed.
-        namespace inner{
+        // Namespaces within LIBC_NAMESPACE namespace are allowed.
+        namespace inner {
             int localVar = 0;
         }
         // Functions with C linkage are allowed.
-        extern "C" void str_fuzz(){}
+        extern "C" void str_fuzz() {}
     }
 
-    // Incorrect: implementation not in a namespace.
+    // Incorrect: implementation not in the LIBC_NAMESPACE namespace.
     void LLVM_LIBC_ENTRYPOINT(strcpy)(char *dest, const char *src) {}
 
-    // Incorrect: outer most namespace is not correct.
+    // Incorrect: outer most namespace is not the LIBC_NAMESPACE macro.
     namespace something_else {
         void LLVM_LIBC_ENTRYPOINT(strcpy)(char *dest, const char *src) {}
     }
+
+    // Incorrect: outer most namespace expansion does not start with `__llvm_libc`.
+    #define LIBC_NAMESPACE custom_namespace
+    namespace LIBC_NAMESPACE {
+        void LLVM_LIBC_ENTRYPOINT(strcpy)(char *dest, const char *src) {}
+    }
diff --git a/clang-tools-extra/test/clang-tidy/checkers/llvmlibc/implementation-in-namespace.cpp b/clang-tools-extra/test/clang-tidy/checkers/llvmlibc/implementation-in-namespace.cpp
index e75556a623b655c..16c5f9ca1067ec5 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/llvmlibc/implementation-in-namespace.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/llvmlibc/implementation-in-namespace.cpp
@@ -3,18 +3,18 @@
 #define MACRO_A "defining macros outside namespace is valid"
 
 class ClassB;
-// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration must be declared within the '__llvm_libc' namespace
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration must be declared within a namespace starting with '__llvm_libc'
 struct StructC {};
-// CHECK-MESSAGES: :[[@LINE-1]]:8: warning: declaration must be declared within the '__llvm_libc' namespace
+// CHECK-MESSAGES: :[[@LINE-1]]:8: warning: declaration must be declared within a namespace starting with '__llvm_libc'
 char *VarD = MACRO_A;
-// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration must be declared within the '__llvm_libc' namespace
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: declaration must be declared within a namespace starting with '__llvm_libc'
 typedef int typeE;
-// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: declaration must be declared within the '__llvm_libc' namespace
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: declaration must be declared within a namespace starting with '__llvm_libc'
 void funcF() {}
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: declaration must be declared within the '__llvm_libc' namespace
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: declaration must be declared within a namespace starting with '__llvm_libc'
 
 namespace namespaceG {
-// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: '__llvm_libc' needs to be the outermost namespace
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: the outermost namespace should be the 'LIBC_NAMESPACE' macro
 namespace __llvm_libc{
 namespace namespaceH {
 class ClassB;
@@ -26,9 +26,20 @@ typedef int typeE;
 void funcF() {}
 } // namespace namespaceG
 
-// Wrapped in correct namespace.
-namespace __llvm_libc {
-// Namespaces within __llvim_libc namespace allowed.
+// Wrapped in macro namespace but with an incorrect name
+#define LIBC_NAMESPACE custom_namespace
+namespace LIBC_NAMESPACE {
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: the outermost namespace should start with '__llvm_libc'
+namespace namespaceH {
+class ClassB;
+} // namespace namespaceH
+} // namespace LIBC_NAMESPACE
+
+
+// Wrapped in macro namespace with a valid name, LIBC_NAMESPACE starts with '__llvm_libc'
+#undef LIBC_NAMESPACE
+#define LIBC_NAMESPACE __llvm_libc_xyz
+namespace LIBC_NAMESPACE {
 namespace namespaceI {
 class ClassB;
 } // namespace namespaceI
@@ -37,4 +48,4 @@ char *VarD = MACRO_A;
 typedef int typeE;
 void funcF() {}
 extern "C" void extern_funcJ() {}
-} // namespace __llvm_libc
+} // namespace LIBC_NAMESPACE

[carlosgalvezp]

Should this change be reflected in the Release Notes?

[gchatelet]

Should this change be reflected in the Release Notes?

Where would that be? clang-tools-extra/docs/ReleaseNotes.rst?
I can't find what the current release notes look like for head.

[PiotrZSL]

Where would that be? clang-tools-extra/docs/ReleaseNotes.rst? I can't find what the current release notes look like for head.

Yes, it's deployed here: https://clang.llvm.org/extra/ReleaseNotes.html

[PiotrZSL]

As a single small change to make hardcoded namespaces configurable looks fine.
I added some comments related to overall issues in this check.
Fell free to fix them or ignore them.

[gchatelet]

As a single small change to make hardcoded namespaces configurable looks fine. I added some comments related to overall issues in this check. Fell free to fix them or ignore them.

@PiotrZSL Thx for the review! I had to restructure the code a bit to accommodate for anonymous namespaces (they generate an implict UsingDirectiveDecl that was triggering the warning twice).

Let me know what you think.

[PiotrZSL]

LGTM