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//===--- RedundantStrcatCallsCheck.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 "RedundantStrcatCallsCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace abseil {
// TODO: Features to add to the check:
// - Make it work if num_args > 26.
// - Remove empty literal string arguments.
// - Collapse consecutive literal string arguments into one (remove the ,).
// - Replace StrCat(a + b) -> StrCat(a, b) if a or b are strings.
// - Make it work in macros if the outer and inner StrCats are both in the
// argument.
void RedundantStrcatCallsCheck::registerMatchers(MatchFinder* Finder) {
const auto CallToStrcat =
callExpr(callee(functionDecl(hasName("::absl::StrCat"))));
const auto CallToStrappend =
callExpr(callee(functionDecl(hasName("::absl::StrAppend"))));
// Do not match StrCat() calls that are descendants of other StrCat calls.
// Those are handled on the ancestor call.
const auto CallToEither = callExpr(
callee(functionDecl(hasAnyName("::absl::StrCat", "::absl::StrAppend"))));
Finder->addMatcher(
callExpr(CallToStrcat, unless(hasAncestor(CallToEither))).bind("StrCat"),
this);
Finder->addMatcher(CallToStrappend.bind("StrAppend"), this);
}
namespace {
struct StrCatCheckResult {
int NumCalls = 0;
std::vector<FixItHint> Hints;
};
void removeCallLeaveArgs(const CallExpr *Call, StrCatCheckResult *CheckResult) {
if (Call->getNumArgs() == 0)
return;
// Remove 'Foo('
CheckResult->Hints.push_back(
FixItHint::CreateRemoval(CharSourceRange::getCharRange(
Call->getBeginLoc(), Call->getArg(0)->getBeginLoc())));
// Remove the ')'
CheckResult->Hints.push_back(
FixItHint::CreateRemoval(CharSourceRange::getCharRange(
Call->getRParenLoc(), Call->getEndLoc().getLocWithOffset(1))));
}
const clang::CallExpr *processArgument(const Expr *Arg,
const MatchFinder::MatchResult &Result,
StrCatCheckResult *CheckResult) {
const auto IsAlphanum = hasDeclaration(cxxMethodDecl(hasName("AlphaNum")));
static const auto* const Strcat = new auto(hasName("::absl::StrCat"));
const auto IsStrcat = cxxBindTemporaryExpr(
has(callExpr(callee(functionDecl(*Strcat))).bind("StrCat")));
if (const auto *SubStrcatCall = selectFirst<const CallExpr>(
"StrCat",
match(stmt(traverse(TK_AsIs,
anyOf(cxxConstructExpr(IsAlphanum,
hasArgument(0, IsStrcat)),
IsStrcat))),
*Arg->IgnoreParenImpCasts(), *Result.Context))) {
removeCallLeaveArgs(SubStrcatCall, CheckResult);
return SubStrcatCall;
}
return nullptr;
}
StrCatCheckResult processCall(const CallExpr *RootCall, bool IsAppend,
const MatchFinder::MatchResult &Result) {
StrCatCheckResult CheckResult;
std::deque<const CallExpr*> CallsToProcess = {RootCall};
while (!CallsToProcess.empty()) {
++CheckResult.NumCalls;
const CallExpr* CallExpr = CallsToProcess.front();
CallsToProcess.pop_front();
int StartArg = CallExpr == RootCall && IsAppend;
for (const auto *Arg : CallExpr->arguments()) {
if (StartArg-- > 0)
continue;
if (const clang::CallExpr *Sub =
processArgument(Arg, Result, &CheckResult)) {
CallsToProcess.push_back(Sub);
}
}
}
return CheckResult;
}
} // namespace
void RedundantStrcatCallsCheck::check(const MatchFinder::MatchResult& Result) {
bool IsAppend;
const CallExpr* RootCall;
if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrCat")))
IsAppend = false;
else if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrAppend")))
IsAppend = true;
else
return;
if (RootCall->getBeginLoc().isMacroID()) {
// Ignore calls within macros.
// In many cases the outer StrCat part of the macro and the inner StrCat is
// a macro argument. Removing the inner StrCat() converts one macro
// argument into many.
return;
}
const StrCatCheckResult CheckResult = processCall(RootCall, IsAppend, Result);
if (CheckResult.NumCalls == 1) {
// Just one call, so nothing to fix.
return;
}
diag(RootCall->getBeginLoc(),
"multiple calls to 'absl::StrCat' can be flattened into a single call")
<< CheckResult.Hints;
}
} // namespace abseil
} // namespace tidy
} // namespace clang
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