[clang-tools-extra] 4cb25e2 - [clang-tidy] Add avoid-pragma-once. (#140388)
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Mon May 26 14:57:54 PDT 2025
Author: Tommy Chen
Date: 2025-05-27T05:57:51+08:00
New Revision: 4cb25e2d37496a5f52a62a1f411a04dac20a8666
URL: https://github.com/llvm/llvm-project/commit/4cb25e2d37496a5f52a62a1f411a04dac20a8666
DIFF: https://github.com/llvm/llvm-project/commit/4cb25e2d37496a5f52a62a1f411a04dac20a8666.diff
LOG: [clang-tidy] Add avoid-pragma-once. (#140388)
#139618
Added:
clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.cpp
clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.h
clang-tools-extra/docs/clang-tidy/checks/portability/avoid-pragma-once.rst
clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib0.h
clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib1.h
clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib2.h
clang-tools-extra/test/clang-tidy/checkers/portability/avoid-pragma-once.cpp
Modified:
clang-tools-extra/clang-tidy/portability/CMakeLists.txt
clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp
clang-tools-extra/docs/ReleaseNotes.rst
clang-tools-extra/docs/clang-tidy/checks/list.rst
Removed:
################################################################################
diff --git a/clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.cpp b/clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.cpp
new file mode 100644
index 0000000000000..d9569d0b5c603
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.cpp
@@ -0,0 +1,47 @@
+//===--- AvoidPragmaOnceCheck.cpp - clang-tidy ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "AvoidPragmaOnceCheck.h"
+
+#include "clang/Basic/SourceManager.h"
+#include "clang/Lex/PPCallbacks.h"
+#include "clang/Lex/Preprocessor.h"
+#include "llvm/ADT/StringRef.h"
+
+namespace clang::tidy::portability {
+
+class PragmaOnceCallbacks : public PPCallbacks {
+public:
+ PragmaOnceCallbacks(AvoidPragmaOnceCheck *Check, const SourceManager &SM)
+ : Check(Check), SM(SM) {}
+ void PragmaDirective(SourceLocation Loc,
+ PragmaIntroducerKind Introducer) override {
+ auto Str = llvm::StringRef(SM.getCharacterData(Loc));
+ if (!Str.consume_front("#"))
+ return;
+ Str = Str.trim();
+ if (!Str.consume_front("pragma"))
+ return;
+ Str = Str.trim();
+ if (Str.starts_with("once"))
+ Check->diag(Loc,
+ "avoid 'pragma once' directive; use include guards instead");
+ }
+
+private:
+ AvoidPragmaOnceCheck *Check;
+ const SourceManager &SM;
+};
+
+void AvoidPragmaOnceCheck::registerPPCallbacks(const SourceManager &SM,
+ Preprocessor *PP,
+ Preprocessor *ModuleExpanderPP) {
+ PP->addPPCallbacks(std::make_unique<PragmaOnceCallbacks>(this, SM));
+}
+
+} // namespace clang::tidy::portability
diff --git a/clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.h b/clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.h
new file mode 100644
index 0000000000000..203fdfd4bd33a
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/portability/AvoidPragmaOnceCheck.h
@@ -0,0 +1,36 @@
+//===--- AvoidPragmaOnceCheck.h - clang-tidy --------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_AVOIDPRAGMAONCECHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_AVOIDPRAGMAONCECHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::portability {
+
+/// Finds uses of ``#pragma once`` and suggests replacing them with standard
+/// include guards (``#ifndef``/``#define``/``#endif``) for improved
+/// portability.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/portability/avoid-pragma-once.html
+class AvoidPragmaOnceCheck : public ClangTidyCheck {
+public:
+ AvoidPragmaOnceCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+ return LangOpts.CPlusPlus || LangOpts.C99;
+ }
+
+ void registerPPCallbacks(const SourceManager &SM, Preprocessor *PP,
+ Preprocessor *ModuleExpanderPP) override;
+};
+
+} // namespace clang::tidy::portability
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_AVOIDPRAGMAONCECHECK_H
diff --git a/clang-tools-extra/clang-tidy/portability/CMakeLists.txt b/clang-tools-extra/clang-tidy/portability/CMakeLists.txt
index 5a38722a61481..73d74a550afc0 100644
--- a/clang-tools-extra/clang-tidy/portability/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/portability/CMakeLists.txt
@@ -5,6 +5,7 @@ set(LLVM_LINK_COMPONENTS
)
add_clang_library(clangTidyPortabilityModule STATIC
+ AvoidPragmaOnceCheck.cpp
PortabilityTidyModule.cpp
RestrictSystemIncludesCheck.cpp
SIMDIntrinsicsCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp b/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp
index 316b98b46cf3f..a15cb36dfdaff 100644
--- a/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp
@@ -9,6 +9,7 @@
#include "../ClangTidy.h"
#include "../ClangTidyModule.h"
#include "../ClangTidyModuleRegistry.h"
+#include "AvoidPragmaOnceCheck.h"
#include "RestrictSystemIncludesCheck.h"
#include "SIMDIntrinsicsCheck.h"
#include "StdAllocatorConstCheck.h"
@@ -20,6 +21,8 @@ namespace portability {
class PortabilityModule : public ClangTidyModule {
public:
void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+ CheckFactories.registerCheck<AvoidPragmaOnceCheck>(
+ "portability-avoid-pragma-once");
CheckFactories.registerCheck<RestrictSystemIncludesCheck>(
"portability-restrict-system-includes");
CheckFactories.registerCheck<SIMDIntrinsicsCheck>(
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 34a13149c9821..d6f2d2b37624e 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -136,6 +136,12 @@ New checks
Finds unintended character output from ``unsigned char`` and ``signed char``
to an ``ostream``.
+- New :doc:`portability-avoid-pragma-once
+ <clang-tidy/checks/portability/avoid-pragma-once>` check.
+
+ Finds uses of ``#pragma once`` and suggests replacing them with standard
+ include guards (``#ifndef``/``#define``/``#endif``) for improved portability.
+
- New :doc:`readability-ambiguous-smartptr-reset-call
<clang-tidy/checks/readability/ambiguous-smartptr-reset-call>` check.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index 1ec476eef3420..5a79d61b1fd7e 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -351,6 +351,7 @@ Clang-Tidy Checks
:doc:`performance-type-promotion-in-math-fn <performance/type-promotion-in-math-fn>`, "Yes"
:doc:`performance-unnecessary-copy-initialization <performance/unnecessary-copy-initialization>`, "Yes"
:doc:`performance-unnecessary-value-param <performance/unnecessary-value-param>`, "Yes"
+ :doc:`portability-avoid-pragma-once <portability/avoid-pragma-once>`,
:doc:`portability-restrict-system-includes <portability/restrict-system-includes>`, "Yes"
:doc:`portability-simd-intrinsics <portability/simd-intrinsics>`,
:doc:`portability-std-allocator-const <portability/std-allocator-const>`,
diff --git a/clang-tools-extra/docs/clang-tidy/checks/portability/avoid-pragma-once.rst b/clang-tools-extra/docs/clang-tidy/checks/portability/avoid-pragma-once.rst
new file mode 100644
index 0000000000000..273286ae8c6b0
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/portability/avoid-pragma-once.rst
@@ -0,0 +1,35 @@
+.. title:: clang-tidy - portability-avoid-pragma-once
+
+portability-avoid-pragma-once
+=============================
+
+Finds uses of ``#pragma once`` and suggests replacing them with standard
+include guards (``#ifndef``/``#define``/``#endif``) for improved portability.
+
+``#pragma once`` is a non-standard extension, despite being widely supported
+by modern compilers. Relying on it can lead to portability issues in
+some environments.
+
+Some older or specialized C/C++ compilers, particularly in embedded systems,
+may not fully support ``#pragma once``.
+
+It can also fail in certain file system configurations, like network drives
+or complex symbolic links, potentially leading to compilation issues.
+
+Consider the following header file:
+
+.. code:: c++
+
+ // my_header.h
+ #pragma once // warning: avoid 'pragma once' directive; use include guards instead
+
+
+The warning suggests using include guards:
+
+.. code:: c++
+
+ // my_header.h
+ #ifndef PATH_TO_MY_HEADER_H // Good: use include guards.
+ #define PATH_TO_MY_HEADER_H
+
+ #endif // PATH_TO_MY_HEADER_H
diff --git a/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib0.h b/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib0.h
new file mode 100644
index 0000000000000..6f70f09beec22
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib0.h
@@ -0,0 +1 @@
+#pragma once
diff --git a/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib1.h b/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib1.h
new file mode 100644
index 0000000000000..bd25511851d96
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib1.h
@@ -0,0 +1 @@
+# pragma once
diff --git a/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib2.h b/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib2.h
new file mode 100644
index 0000000000000..bd47bc5c36795
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/portability/Inputs/avoid-pragma-once/lib2.h
@@ -0,0 +1 @@
+# pragma once
diff --git a/clang-tools-extra/test/clang-tidy/checkers/portability/avoid-pragma-once.cpp b/clang-tools-extra/test/clang-tidy/checkers/portability/avoid-pragma-once.cpp
new file mode 100644
index 0000000000000..3fc8e8a2421eb
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/portability/avoid-pragma-once.cpp
@@ -0,0 +1,15 @@
+// RUN: %check_clang_tidy %s portability-avoid-pragma-once %t \
+// RUN: -- --header-filter='.*' -- -I%S/Inputs/avoid-pragma-once
+
+// #pragma once
+#include "lib0.h"
+// CHECK-MESSAGES: lib0.h:1:1: warning: avoid 'pragma once' directive; use include guards instead
+
+
+// # pragma once
+#include "lib1.h"
+// CHECK-MESSAGES: lib1.h:1:1: warning: avoid 'pragma once' directive; use include guards instead
+
+// # pragma once
+#include "lib2.h"
+// CHECK-MESSAGES: lib2.h:1:1: warning: avoid 'pragma once' directive; use include guards instead
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