https://github.com/hjanuschka updated
https://github.com/llvm/llvm-project/pull/120055
>From 8b2dc9adf4fae2065823e5beb3a1cd851686913c Mon Sep 17 00:00:00 2001
From: Helmut Januschka <hel...@januschka.com>
Date: Mon, 16 Dec 2024 08:24:14 +0100
Subject: [PATCH 1/2] [clang-tidy] Add readability-string-view-substr check
Add a new check that suggests using string_view::remove_prefix() and
remove_suffix() instead of substr() when the intent is to remove
characters from either end of a string_view.
---
.../clang-tidy/readability/CMakeLists.txt | 1 +
.../readability/ReadabilityTidyModule.cpp | 3 +
.../readability/StringViewSubstrCheck.cpp | 132 ++++++++++++++++++
.../readability/StringViewSubstrCheck.h | 39 ++++++
clang-tools-extra/docs/ReleaseNotes.rst | 7 +
.../checks/readability/string-view-substr.rst | 16 +++
.../readability/stringview_substr.cpp | 55 ++++++++
7 files changed, 253 insertions(+)
create mode 100644
clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
create mode 100644
clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.h
create mode 100644
clang-tools-extra/docs/clang-tidy/checks/readability/string-view-substr.rst
create mode 100644
clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
diff --git a/clang-tools-extra/clang-tidy/readability/CMakeLists.txt
b/clang-tools-extra/clang-tidy/readability/CMakeLists.txt
index 8f303c51e1b0da..8b44fc339441ac 100644
--- a/clang-tools-extra/clang-tidy/readability/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/readability/CMakeLists.txt
@@ -53,6 +53,7 @@ add_clang_library(clangTidyReadabilityModule STATIC
StaticAccessedThroughInstanceCheck.cpp
StaticDefinitionInAnonymousNamespaceCheck.cpp
StringCompareCheck.cpp
+ StringViewSubstrCheck.cpp
SuspiciousCallArgumentCheck.cpp
UniqueptrDeleteReleaseCheck.cpp
UppercaseLiteralSuffixCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
index d61c0ba39658e5..f36ec8f95ede60 100644
--- a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
@@ -56,6 +56,7 @@
#include "StaticAccessedThroughInstanceCheck.h"
#include "StaticDefinitionInAnonymousNamespaceCheck.h"
#include "StringCompareCheck.h"
+#include "StringViewSubstrCheck.h"
#include "SuspiciousCallArgumentCheck.h"
#include "UniqueptrDeleteReleaseCheck.h"
#include "UppercaseLiteralSuffixCheck.h"
@@ -146,6 +147,8 @@ class ReadabilityModule : public ClangTidyModule {
"readability-static-definition-in-anonymous-namespace");
CheckFactories.registerCheck<StringCompareCheck>(
"readability-string-compare");
+ CheckFactories.registerCheck<StringViewSubstrCheck>(
+ "readability-stringview-substr");
CheckFactories.registerCheck<readability::NamedParameterCheck>(
"readability-named-parameter");
CheckFactories.registerCheck<NonConstParameterCheck>(
diff --git a/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
b/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
new file mode 100644
index 00000000000000..e86a971695a835
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
@@ -0,0 +1,132 @@
+//===--- StringViewSubstrCheck.cpp - 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "StringViewSubstrCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+void StringViewSubstrCheck::registerMatchers(MatchFinder *Finder) {
+ const auto HasStringViewType =
hasType(hasUnqualifiedDesugaredType(recordType(
+ hasDeclaration(recordDecl(hasName("::std::basic_string_view"))))));
+
+ // Match assignment to string_view's substr
+ Finder->addMatcher(
+ cxxOperatorCallExpr(
+ hasOverloadedOperatorName("="),
+ hasArgument(0, expr(HasStringViewType).bind("target")),
+ hasArgument(
+ 1, cxxMemberCallExpr(callee(memberExpr(hasDeclaration(
+ cxxMethodDecl(hasName("substr"))))),
+ on(expr(HasStringViewType).bind("source")))
+ .bind("substr_call")))
+ .bind("assignment"),
+ this);
+}
+
+void StringViewSubstrCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto *Assignment =
+ Result.Nodes.getNodeAs<CXXOperatorCallExpr>("assignment");
+ const auto *Target = Result.Nodes.getNodeAs<Expr>("target");
+ const auto *Source = Result.Nodes.getNodeAs<Expr>("source");
+ const auto *SubstrCall =
+ Result.Nodes.getNodeAs<CXXMemberCallExpr>("substr_call");
+
+ if (!Assignment || !Target || !Source || !SubstrCall) {
+ return;
+ }
+
+ // Get the DeclRefExpr for the target and source to compare variables
+ const auto *TargetDRE = dyn_cast<DeclRefExpr>(Target->IgnoreParenImpCasts());
+ const auto *SourceDRE = dyn_cast<DeclRefExpr>(Source->IgnoreParenImpCasts());
+
+ // Only handle self-assignment cases
+ if (!TargetDRE || !SourceDRE ||
+ TargetDRE->getDecl() != SourceDRE->getDecl()) {
+ return;
+ }
+
+ const Expr *StartArg = SubstrCall->getArg(0);
+ const Expr *LengthArg =
+ SubstrCall->getNumArgs() > 1 ? SubstrCall->getArg(1) : nullptr;
+
+ // Get source text of first argument
+ std::string StartText =
+ Lexer::getSourceText(
+ CharSourceRange::getTokenRange(StartArg->getSourceRange()),
+ *Result.SourceManager, Result.Context->getLangOpts())
+ .str();
+
+ // Case 1: Check for remove_prefix pattern - only when the second arg is
+ // missing (uses npos)
+ if (!LengthArg || isa<CXXDefaultArgExpr>(LengthArg)) {
+ std::string Replacement = TargetDRE->getNameInfo().getAsString() +
+ ".remove_prefix(" + StartText + ")";
+ diag(Assignment->getBeginLoc(), "prefer 'remove_prefix' over 'substr' for "
+ "removing characters from the start")
+ << FixItHint::CreateReplacement(Assignment->getSourceRange(),
+ Replacement);
+ return;
+ }
+
+ // Case 2: Check for remove_suffix pattern
+ if (StartText == "0") {
+ if (const auto *BinOp = dyn_cast<BinaryOperator>(LengthArg)) {
+ if (BinOp->getOpcode() == BO_Sub) {
+ const Expr *LHS = BinOp->getLHS();
+ const Expr *RHS = BinOp->getRHS();
+
+ // Check if LHS is a length() call on the same string_view
+ if (const auto *LengthCall = dyn_cast<CXXMemberCallExpr>(LHS)) {
+ if (const auto *LengthMethod =
+ dyn_cast<CXXMethodDecl>(LengthCall->getDirectCallee())) {
+ if (LengthMethod->getName() == "length") {
+ // Verify the length() call is on the same string_view
+ const Expr *LengthObject =
+ LengthCall->getImplicitObjectArgument();
+ const auto *LengthDRE =
+ dyn_cast<DeclRefExpr>(LengthObject->IgnoreParenImpCasts());
+
+ if (!LengthDRE || LengthDRE->getDecl() != TargetDRE->getDecl()) {
+ return;
+ }
+
+ // Must be a simple non-zero integer literal
+ const auto *IL =
+ dyn_cast<IntegerLiteral>(RHS->IgnoreParenImpCasts());
+ if (!IL || IL->getValue() == 0) {
+ return;
+ }
+
+ std::string RHSText =
+ Lexer::getSourceText(
+ CharSourceRange::getTokenRange(RHS->getSourceRange()),
+ *Result.SourceManager, Result.Context->getLangOpts())
+ .str();
+
+ std::string Replacement = TargetDRE->getNameInfo().getAsString()
+
+ ".remove_suffix(" + RHSText + ")";
+ diag(Assignment->getBeginLoc(),
+ "prefer 'remove_suffix' over 'substr' for removing "
+ "characters from the end")
+ << FixItHint::CreateReplacement(Assignment->getSourceRange(),
+ Replacement);
+ return;
+ }
+ }
+ }
+ }
+ }
+ }
+}
+
+} // namespace clang::tidy::readability
diff --git a/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.h
b/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.h
new file mode 100644
index 00000000000000..1a2054da1ed9cc
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.h
@@ -0,0 +1,39 @@
+//===--- StringViewSubstrCheck.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_READABILITY_STRINGVIEWSUBSTRCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_STRINGVIEWSUBSTRCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::readability {
+
+/// Finds string_view substr() calls that can be replaced with remove_prefix()
+/// or remove_suffix().
+///
+/// For the user-facing documentation see:
+///
https://clang.llvm.org/extra/clang-tidy/checks/readability/string-view-substr.html
+///
+/// The check matches two patterns:
+/// sv = sv.substr(N) -> sv.remove_prefix(N)
+/// sv = sv.substr(0, sv.length() - N) -> sv.remove_suffix(N)
+///
+/// These replacements make the intent clearer and are more efficient as they
+/// modify the string_view in place rather than creating a new one.
+class StringViewSubstrCheck : public ClangTidyCheck {
+public:
+ StringViewSubstrCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace clang::tidy::readability
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_STRINGVIEWSUBSTRCHECK_H
\ No newline at end of file
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst
b/clang-tools-extra/docs/ReleaseNotes.rst
index 453a91e3b504cd..4eb6c98bcf461b 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -136,6 +136,13 @@ New checks
Gives warnings for tagged unions, where the number of tags is
different from the number of data members inside the union.
+- New :doc:`readability-string-view-substr
+ <clang-tidy/checks/readability/string-view-substr>` check.
+
+ Finds ``std::string_view::substr()`` calls that can be replaced with clearer
+ alternatives using ``remove_prefix()`` or ``remove_suffix()``. This makes
the
+ intent clearer and is more efficient as it modifies the string_view in place.
+
- New :doc:`portability-template-virtual-member-function
<clang-tidy/checks/portability/template-virtual-member-function>` check.
diff --git
a/clang-tools-extra/docs/clang-tidy/checks/readability/string-view-substr.rst
b/clang-tools-extra/docs/clang-tidy/checks/readability/string-view-substr.rst
new file mode 100644
index 00000000000000..f29bcbacc0d7d1
--- /dev/null
+++
b/clang-tools-extra/docs/clang-tidy/checks/readability/string-view-substr.rst
@@ -0,0 +1,16 @@
+.. title:: clang-tidy - readability-string-view-substr
+
+readability-string-view-substr
+==============================
+
+Finds ``string_view substr()`` calls that can be replaced with clearer
alternatives
+using ``remove_prefix()`` or ``remove_suffix()``.
+
+The check suggests the following transformations:
+
+=========================================== =======================
+Expression Replacement
+=========================================== =======================
+``sv = sv.substr(n)`` ``sv.remove_prefix(n)``
+``sv = sv.substr(0, sv.length()-n)`` ``sv.remove_suffix(n)``
+=========================================== =======================
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
b/clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
new file mode 100644
index 00000000000000..274c305b640803
--- /dev/null
+++
b/clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
@@ -0,0 +1,55 @@
+// RUN: %check_clang_tidy %s readability-stringview-substr %t
+
+namespace std {
+template <typename T>
+class basic_string_view {
+public:
+ using size_type = unsigned long;
+ static constexpr size_type npos = -1;
+
+ basic_string_view(const char*) {}
+ basic_string_view substr(size_type pos, size_type count = npos) const {
return *this; }
+ void remove_prefix(size_type n) {}
+ void remove_suffix(size_type n) {}
+ size_type length() const { return 0; }
+
+ // Needed for assignment operator
+ basic_string_view& operator=(const basic_string_view&) { return *this; }
+};
+
+using string_view = basic_string_view<char>;
+}
+
+void test() {
+ std::string_view sv("test");
+ std::string_view sv1("test");
+ std::string_view sv2("other");
+
+ // Should match: Removing N characters from start
+ sv = sv.substr(5);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_prefix' over
'substr' for removing characters from the start [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_prefix(5)
+
+ // Should match: Removing N characters from end
+ sv = sv.substr(0, sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ // Should not match: Basic substring operations
+ sv = sv.substr(0, 3); // No warning - taking first N characters
+ sv = sv.substr(1, 3); // No warning - taking N characters from position 1
+
+ // Should not match: Operations on different string_views
+ sv = sv2.substr(0, sv2.length() - 3); // No warning - not self-assignment
+ sv = sv.substr(0, sv2.length() - 3); // No warning - length() from
different string_view
+ sv1 = sv1.substr(0, sv2.length() - 3); // No warning - length() from
different string_view
+ sv = sv1.substr(0, sv1.length() - 3); // No warning - not self-assignment
+
+ // Should not match: Not actually removing from end
+ sv = sv.substr(0, sv.length()); // No warning - keeping entire string
+ sv = sv.substr(0, sv.length() - 0); // No warning - subtracting zero
+
+ // Should not match: Complex expressions
+ sv = sv.substr(0, sv.length() - (3 + 2)); // No warning - complex arithmetic
+ sv = sv.substr(1 + 2, sv.length() - 3); // No warning - complex start
position
+}
>From 64931c696fe64cdb8a7571029eea0cc40592a663 Mon Sep 17 00:00:00 2001
From: Helmut Januschka <hel...@januschka.com>
Date: Mon, 16 Dec 2024 11:14:12 +0100
Subject: [PATCH 2/2] up
---
.../readability/StringViewSubstrCheck.cpp | 19 ++++++++-
.../readability/stringview_substr.cpp | 41 +++++++++++++++++++
2 files changed, 59 insertions(+), 1 deletion(-)
diff --git a/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
b/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
index e86a971695a835..01c3895f61f5c4 100644
--- a/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/StringViewSubstrCheck.cpp
@@ -79,7 +79,24 @@ void StringViewSubstrCheck::check(const
MatchFinder::MatchResult &Result) {
}
// Case 2: Check for remove_suffix pattern
- if (StartText == "0") {
+ const Expr *Start = StartArg->IgnoreParenImpCasts();
+ bool IsZero = false;
+
+ if (const auto *IL = dyn_cast<IntegerLiteral>(Start)) {
+ IsZero = IL->getValue() == 0;
+ } else if (const auto *DRE = dyn_cast<DeclRefExpr>(Start)) {
+ // Check constants
+ if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
+ if (VD->hasInit()) {
+ if (const auto *Init = dyn_cast<IntegerLiteral>(
+ VD->getInit()->IgnoreParenImpCasts())) {
+ IsZero = Init->getValue() == 0;
+ }
+ }
+ }
+ }
+
+ if (IsZero) {
if (const auto *BinOp = dyn_cast<BinaryOperator>(LengthArg)) {
if (BinOp->getOpcode() == BO_Sub) {
const Expr *LHS = BinOp->getLHS();
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
b/clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
index 274c305b640803..2c1d9df3711b1d 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/readability/stringview_substr.cpp
@@ -53,3 +53,44 @@ void test() {
sv = sv.substr(0, sv.length() - (3 + 2)); // No warning - complex arithmetic
sv = sv.substr(1 + 2, sv.length() - 3); // No warning - complex start
position
}
+
+void test_zeros() {
+ std::string_view sv("test");
+ const int kZero = 0;
+ constexpr std::string_view::size_type Zero = 0; // Fixed: using
string_view::size_type
+ #define START_POS 0
+
+ // All of these should match remove_suffix pattern and trigger warnings
+ sv = sv.substr(0, sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ sv = sv.substr(kZero, sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ sv = sv.substr(Zero, sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ sv = sv.substr(START_POS, sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ sv = sv.substr((0), sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ sv = sv.substr(0u, sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ sv = sv.substr(0UL, sv.length() - 3);
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer 'remove_suffix' over
'substr' for removing characters from the end [readability-stringview-substr]
+ // CHECK-FIXES: sv.remove_suffix(3)
+
+ // These should NOT match the remove_suffix pattern
+ sv = sv.substr(1-1, sv.length() - 3); // No warning - complex expression
+ sv = sv.substr(sv.length() - 3, sv.length() - 3); // No warning - non-zero
start
+}
+
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