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| //===--- InfiniteLoopCheck.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 "InfiniteLoopCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace bugprone {
static internal::Matcher<Stmt>
loopEndingStmt(internal::Matcher<Stmt> Internal) {
return stmt(anyOf(breakStmt(Internal), returnStmt(Internal),
gotoStmt(Internal), cxxThrowExpr(Internal),
callExpr(Internal, callee(functionDecl(isNoReturn())))));
}
/// Return whether `S` is a reference to the declaration of `Var`.
static bool isAccessForVar(const Stmt *S, const VarDecl *Var) {
if (const auto *DRE = dyn_cast<DeclRefExpr>(S))
return DRE->getDecl() == Var;
return false;
}
/// Return whether `Var` has a pointer or reference in `S`.
static bool isPtrOrReferenceForVar(const Stmt *S, const VarDecl *Var) {
if (const auto *DS = dyn_cast<DeclStmt>(S)) {
for (const Decl *D : DS->getDeclGroup()) {
if (const auto *LeftVar = dyn_cast<VarDecl>(D)) {
if (LeftVar->hasInit() && LeftVar->getType()->isReferenceType()) {
return isAccessForVar(LeftVar->getInit(), Var);
}
}
}
} else if (const auto *UnOp = dyn_cast<UnaryOperator>(S)) {
if (UnOp->getOpcode() == UO_AddrOf)
return isAccessForVar(UnOp->getSubExpr(), Var);
}
return false;
}
/// Return whether `Var` has a pointer or reference in `S`.
static bool hasPtrOrReferenceInStmt(const Stmt *S, const VarDecl *Var) {
if (isPtrOrReferenceForVar(S, Var))
return true;
for (const Stmt *Child : S->children()) {
if (!Child)
continue;
if (hasPtrOrReferenceInStmt(Child, Var))
return true;
}
return false;
}
/// Return whether `Var` has a pointer or reference in `Func`.
static bool hasPtrOrReferenceInFunc(const FunctionDecl *Func,
const VarDecl *Var) {
return hasPtrOrReferenceInStmt(Func->getBody(), Var);
}
/// Return whether `Var` was changed in `LoopStmt`.
static bool isChanged(const Stmt *LoopStmt, const VarDecl *Var,
ASTContext *Context) {
if (const auto *ForLoop = dyn_cast<ForStmt>(LoopStmt))
return (ForLoop->getInc() &&
ExprMutationAnalyzer(*ForLoop->getInc(), *Context)
.isMutated(Var)) ||
(ForLoop->getBody() &&
ExprMutationAnalyzer(*ForLoop->getBody(), *Context)
.isMutated(Var)) ||
(ForLoop->getCond() &&
ExprMutationAnalyzer(*ForLoop->getCond(), *Context).isMutated(Var));
return ExprMutationAnalyzer(*LoopStmt, *Context).isMutated(Var);
}
/// Return whether `Cond` is a variable that is possibly changed in `LoopStmt`.
static bool isVarThatIsPossiblyChanged(const FunctionDecl *Func,
const Stmt *LoopStmt, const Stmt *Cond,
ASTContext *Context) {
if (const auto *DRE = dyn_cast<DeclRefExpr>(Cond)) {
if (const auto *Var = dyn_cast<VarDecl>(DRE->getDecl())) {
if (!Var->isLocalVarDeclOrParm())
return true;
if (Var->getType().isVolatileQualified())
return true;
if (!Var->getType().getTypePtr()->isIntegerType())
return true;
return hasPtrOrReferenceInFunc(Func, Var) ||
isChanged(LoopStmt, Var, Context);
// FIXME: Track references.
}
} else if (isa<MemberExpr>(Cond) || isa<CallExpr>(Cond)) {
// FIXME: Handle MemberExpr.
return true;
}
return false;
}
/// Return whether at least one variable of `Cond` changed in `LoopStmt`.
static bool isAtLeastOneCondVarChanged(const FunctionDecl *Func,
const Stmt *LoopStmt, const Stmt *Cond,
ASTContext *Context) {
if (isVarThatIsPossiblyChanged(Func, LoopStmt, Cond, Context))
return true;
for (const Stmt *Child : Cond->children()) {
if (!Child)
continue;
if (isAtLeastOneCondVarChanged(Func, LoopStmt, Child, Context))
return true;
}
return false;
}
/// Return the variable names in `Cond`.
static std::string getCondVarNames(const Stmt *Cond) {
if (const auto *DRE = dyn_cast<DeclRefExpr>(Cond)) {
if (const auto *Var = dyn_cast<VarDecl>(DRE->getDecl()))
return Var->getName();
}
std::string Result;
for (const Stmt *Child : Cond->children()) {
if (!Child)
continue;
std::string NewNames = getCondVarNames(Child);
if (!Result.empty() && !NewNames.empty())
Result += ", ";
Result += NewNames;
}
return Result;
}
void InfiniteLoopCheck::registerMatchers(MatchFinder *Finder) {
const auto LoopCondition = allOf(
hasCondition(
expr(forFunction(functionDecl().bind("func"))).bind("condition")),
unless(hasBody(hasDescendant(
loopEndingStmt(forFunction(equalsBoundNode("func")))))));
Finder->addMatcher(stmt(anyOf(whileStmt(LoopCondition), doStmt(LoopCondition),
forStmt(LoopCondition)))
.bind("loop-stmt"),
this);
}
void InfiniteLoopCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Cond = Result.Nodes.getNodeAs<Expr>("condition");
const auto *LoopStmt = Result.Nodes.getNodeAs<Stmt>("loop-stmt");
const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
if (isAtLeastOneCondVarChanged(Func, LoopStmt, Cond, Result.Context))
return;
std::string CondVarNames = getCondVarNames(Cond);
if (CondVarNames.empty())
return;
diag(LoopStmt->getBeginLoc(),
"this loop is infinite; none of its condition variables (%0)"
" are updated in the loop body")
<< CondVarNames;
}
} // namespace bugprone
} // namespace tidy
} // namespace clang
|