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//===--- StringConstructorCheck.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 "StringConstructorCheck.h"
#include "../utils/OptionsUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Tooling/FixIt.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace bugprone {
namespace {
AST_MATCHER_P(IntegerLiteral, isBiggerThan, unsigned, N) {
return Node.getValue().getZExtValue() > N;
}
const char DefaultStringNames[] =
"::std::basic_string;::std::basic_string_view";
static std::vector<StringRef>
removeNamespaces(const std::vector<std::string> &Names) {
std::vector<StringRef> Result;
Result.reserve(Names.size());
for (StringRef Name : Names) {
std::string::size_type ColonPos = Name.rfind(':');
Result.push_back(
Name.substr(ColonPos == std::string::npos ? 0 : ColonPos + 1));
}
return Result;
}
} // namespace
StringConstructorCheck::StringConstructorCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
IsStringviewNullptrCheckEnabled(
Context->isCheckEnabled("bugprone-stringview-nullptr")),
WarnOnLargeLength(Options.get("WarnOnLargeLength", true)),
LargeLengthThreshold(Options.get("LargeLengthThreshold", 0x800000)),
StringNames(utils::options::parseStringList(
Options.get("StringNames", DefaultStringNames))) {}
void StringConstructorCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "WarnOnLargeLength", WarnOnLargeLength);
Options.store(Opts, "LargeLengthThreshold", LargeLengthThreshold);
Options.store(Opts, "StringNames", DefaultStringNames);
}
void StringConstructorCheck::registerMatchers(MatchFinder *Finder) {
const auto ZeroExpr = expr(ignoringParenImpCasts(integerLiteral(equals(0))));
const auto CharExpr = expr(ignoringParenImpCasts(characterLiteral()));
const auto NegativeExpr = expr(ignoringParenImpCasts(
unaryOperator(hasOperatorName("-"),
hasUnaryOperand(integerLiteral(unless(equals(0)))))));
const auto LargeLengthExpr = expr(ignoringParenImpCasts(
integerLiteral(isBiggerThan(LargeLengthThreshold))));
const auto CharPtrType = type(anyOf(pointerType(), arrayType()));
// Match a string-literal; even through a declaration with initializer.
const auto BoundStringLiteral = stringLiteral().bind("str");
const auto ConstStrLiteralDecl = varDecl(
isDefinition(), hasType(constantArrayType()), hasType(isConstQualified()),
hasInitializer(ignoringParenImpCasts(BoundStringLiteral)));
const auto ConstPtrStrLiteralDecl = varDecl(
isDefinition(),
hasType(pointerType(pointee(isAnyCharacter(), isConstQualified()))),
hasInitializer(ignoringParenImpCasts(BoundStringLiteral)));
const auto ConstStrLiteral = expr(ignoringParenImpCasts(anyOf(
BoundStringLiteral, declRefExpr(hasDeclaration(anyOf(
ConstPtrStrLiteralDecl, ConstStrLiteralDecl))))));
// Check the fill constructor. Fills the string with n consecutive copies of
// character c. [i.e string(size_t n, char c);].
Finder->addMatcher(
cxxConstructExpr(
hasDeclaration(cxxMethodDecl(hasName("basic_string"))),
hasArgument(0, hasType(qualType(isInteger()))),
hasArgument(1, hasType(qualType(isInteger()))),
anyOf(
// Detect the expression: string('x', 40);
hasArgument(0, CharExpr.bind("swapped-parameter")),
// Detect the expression: string(0, ...);
hasArgument(0, ZeroExpr.bind("empty-string")),
// Detect the expression: string(-4, ...);
hasArgument(0, NegativeExpr.bind("negative-length")),
// Detect the expression: string(0x1234567, ...);
hasArgument(0, LargeLengthExpr.bind("large-length"))))
.bind("constructor"),
this);
// Check the literal string constructor with char pointer and length
// parameters. [i.e. string (const char* s, size_t n);]
Finder->addMatcher(
cxxConstructExpr(
hasDeclaration(cxxConstructorDecl(ofClass(
cxxRecordDecl(hasAnyName(removeNamespaces(StringNames)))))),
hasArgument(0, hasType(CharPtrType)),
hasArgument(1, hasType(isInteger())),
anyOf(
// Detect the expression: string("...", 0);
hasArgument(1, ZeroExpr.bind("empty-string")),
// Detect the expression: string("...", -4);
hasArgument(1, NegativeExpr.bind("negative-length")),
// Detect the expression: string("lit", 0x1234567);
hasArgument(1, LargeLengthExpr.bind("large-length")),
// Detect the expression: string("lit", 5)
allOf(hasArgument(0, ConstStrLiteral.bind("literal-with-length")),
hasArgument(1, ignoringParenImpCasts(
integerLiteral().bind("int"))))))
.bind("constructor"),
this);
// Check the literal string constructor with char pointer.
// [i.e. string (const char* s);]
Finder->addMatcher(
traverse(
TK_AsIs,
cxxConstructExpr(
hasDeclaration(cxxConstructorDecl(ofClass(anyOf(
cxxRecordDecl(hasName("basic_string_view"))
.bind("basic_string_view_decl"),
cxxRecordDecl(hasAnyName(removeNamespaces(StringNames))))))),
hasArgument(0, expr().bind("from-ptr")),
// do not match std::string(ptr, int)
// match std::string(ptr, alloc)
// match std::string(ptr)
anyOf(hasArgument(1, unless(hasType(isInteger()))),
argumentCountIs(1)))
.bind("constructor")),
this);
}
void StringConstructorCheck::check(const MatchFinder::MatchResult &Result) {
const ASTContext &Ctx = *Result.Context;
const auto *E = Result.Nodes.getNodeAs<CXXConstructExpr>("constructor");
assert(E && "missing constructor expression");
SourceLocation Loc = E->getBeginLoc();
if (Result.Nodes.getNodeAs<Expr>("swapped-parameter")) {
const Expr *P0 = E->getArg(0);
const Expr *P1 = E->getArg(1);
diag(Loc, "string constructor parameters are probably swapped;"
" expecting string(count, character)")
<< tooling::fixit::createReplacement(*P0, *P1, Ctx)
<< tooling::fixit::createReplacement(*P1, *P0, Ctx);
} else if (Result.Nodes.getNodeAs<Expr>("empty-string")) {
diag(Loc, "constructor creating an empty string");
} else if (Result.Nodes.getNodeAs<Expr>("negative-length")) {
diag(Loc, "negative value used as length parameter");
} else if (Result.Nodes.getNodeAs<Expr>("large-length")) {
if (WarnOnLargeLength)
diag(Loc, "suspicious large length parameter");
} else if (Result.Nodes.getNodeAs<Expr>("literal-with-length")) {
const auto *Str = Result.Nodes.getNodeAs<StringLiteral>("str");
const auto *Lit = Result.Nodes.getNodeAs<IntegerLiteral>("int");
if (Lit->getValue().ugt(Str->getLength())) {
diag(Loc, "length is bigger than string literal size");
}
} else if (const auto *Ptr = Result.Nodes.getNodeAs<Expr>("from-ptr")) {
Expr::EvalResult ConstPtr;
if (!Ptr->isInstantiationDependent() &&
Ptr->EvaluateAsRValue(ConstPtr, Ctx) &&
((ConstPtr.Val.isInt() && ConstPtr.Val.getInt().isZero()) ||
(ConstPtr.Val.isLValue() && ConstPtr.Val.isNullPointer()))) {
if (IsStringviewNullptrCheckEnabled &&
Result.Nodes.getNodeAs<CXXRecordDecl>("basic_string_view_decl")) {
// Filter out `basic_string_view` to avoid conflicts with
// `bugprone-stringview-nullptr`
return;
}
diag(Loc, "constructing string from nullptr is undefined behaviour");
}
}
}
} // namespace bugprone
} // namespace tidy
} // namespace clang
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