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[clang-tidy] modernize-use-starts-ends-with: fix false positives on find and rfind (#129564)

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Also document cases with two or three arguments (matching default arguments)
this check matches.

Closes https://github.com/llvm/llvm-project/issues/129498.
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Baranov Victor 2025-03-22 15:07:58 +03:00 committed by GitHub
parent 2a4522229c
commit 2909c420f6
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4 changed files with 68 additions and 6 deletions
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24
clang-tools-extra/clang-tidy/modernize/UseStartsEndsWithCheck.cpp
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@ -113,21 +113,33 @@ void UseStartsEndsWithCheck::registerMatchers(MatchFinder *Finder) {
const auto OnClassWithEndsWithFunction = ClassTypeWithMethod(
"ends_with_fun", "ends_with", "endsWith", "endswith", "EndsWith");
// Case 1: X.find(Y) [!=]= 0 -> starts_with.
// Case 1: X.find(Y, [0], [LEN(Y)]) [!=]= 0 -> starts_with.
const auto FindExpr = cxxMemberCallExpr(
anyOf(argumentCountIs(1), hasArgument(1, ZeroLiteral)),
callee(
cxxMethodDecl(hasName("find"), ofClass(OnClassWithStartsWithFunction))
.bind("find_fun")),
hasArgument(0, expr().bind("needle")));
hasArgument(0, expr().bind("needle")),
anyOf(
// Detect the expression: X.find(Y);
argumentCountIs(1),
// Detect the expression: X.find(Y, 0);
allOf(argumentCountIs(2), hasArgument(1, ZeroLiteral)),
// Detect the expression: X.find(Y, 0, LEN(Y));
allOf(argumentCountIs(3), hasArgument(1, ZeroLiteral),
hasArgument(2, lengthExprForStringNode("needle")))));
// Case 2: X.rfind(Y, 0) [!=]= 0 -> starts_with.
// Case 2: X.rfind(Y, 0, [LEN(Y)]) [!=]= 0 -> starts_with.
const auto RFindExpr = cxxMemberCallExpr(
hasArgument(1, ZeroLiteral),
callee(cxxMethodDecl(hasName("rfind"),
ofClass(OnClassWithStartsWithFunction))
.bind("find_fun")),
hasArgument(0, expr().bind("needle")));
hasArgument(0, expr().bind("needle")),
anyOf(
// Detect the expression: X.rfind(Y, 0);
allOf(argumentCountIs(2), hasArgument(1, ZeroLiteral)),
// Detect the expression: X.rfind(Y, 0, LEN(Y));
allOf(argumentCountIs(3), hasArgument(1, ZeroLiteral),
hasArgument(2, lengthExprForStringNode("needle")))));
// Case 3: X.compare(0, LEN(Y), Y) [!=]= 0 -> starts_with.
const auto CompareExpr = cxxMemberCallExpr(

5
clang-tools-extra/docs/ReleaseNotes.rst
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@ -175,6 +175,11 @@ Changes in existing checks
<clang-tidy/checks/modernize/use-ranges>` check by updating suppress
warnings logic for ``nullptr`` in ``std::find``.
- Improved :doc:`modernize-use-starts-ends-with
<clang-tidy/checks/modernize/use-starts-ends-with>` check by adding more
matched scenarios of ``find`` and ``rfind`` methods and fixing false
positives when those methods were called with 3 arguments.
- Improved :doc:`modernize-use-std-numbers
<clang-tidy/checks/modernize/use-std-numbers>` check to support math
functions of different precisions.

3
clang-tools-extra/docs/clang-tidy/checks/modernize/use-starts-ends-with.rst
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@ -13,7 +13,10 @@ Covered scenarios:
Expression Replacement
---------------------------------------------------- ---------------------
``u.find(v) == 0`` ``u.starts_with(v)``
``u.find(v, 0) == 0`` ``u.starts_with(v)``
``u.find(v, 0, v.size()) == 0`` ``u.starts_with(v)``
``u.rfind(v, 0) != 0`` ``!u.starts_with(v)``
``u.rfind(v, 0, v.size()) != 0`` ``!u.starts_with(v)``
``u.compare(0, v.size(), v) == 0`` ``u.starts_with(v)``
``u.substr(0, v.size()) == v`` ``u.starts_with(v)``
``v != u.substr(0, v.size())`` ``!u.starts_with(v)``

42
clang-tools-extra/test/clang-tidy/checkers/modernize/use-starts-ends-with.cpp
View File

@ -236,6 +236,42 @@ void test(std::string s, std::string_view sv, sub_string ss, sub_sub_string sss,
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use ends_with
// CHECK-FIXES: s.ends_with(suffix);
s.find("a", 0) == 0;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: s.starts_with("a");
s.find(s, ZERO) == 0;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: s.starts_with(s);
s.find(s, 0) == ZERO;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: s.starts_with(s);
s.find("aaa", 0, 3) == 0;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: s.starts_with("aaa");
s.find("aaa", ZERO, 3) == 0;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: s.starts_with("aaa");
s.find("aaa", ZERO, strlen(("aaa"))) == ZERO;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: s.starts_with("aaa");
s.rfind("aaa", 0, 3) != 0;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: !s.starts_with("aaa");
s.rfind("aaa", ZERO, 3) != 0;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: !s.starts_with("aaa");
s.rfind("aaa", ZERO, strlen(("aaa"))) == ZERO;
// CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with
// CHECK-FIXES: s.starts_with("aaa");
struct S {
std::string s;
} t;
@ -261,6 +297,12 @@ void test(std::string s, std::string_view sv, sub_string ss, sub_sub_string sss,
#define STRING s
if (0 == STRING.find("ala")) { /* do something */}
// Cases when literal-size and size parameters are different are not being matched.
s.find("aaa", 0, 2) == 0;
s.find("aaa", 0, strlen("aa")) == 0;
s.rfind("aaa", 0, 2) == 0;
s.rfind("aaa", 0, strlen("aa")) == 0;
}
void test_substr() {