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//===-- StrToNumCheck.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 "StrToNumCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/FormatString.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "llvm/ADT/StringSwitch.h"
#include <cassert>
using namespace clang::ast_matchers;
namespace clang::tidy::cert {
void StrToNumCheck::registerMatchers(MatchFinder *Finder) {
// Match any function call to the C standard library string conversion
// functions that do no error checking.
Finder->addMatcher(
callExpr(
callee(functionDecl(anyOf(
functionDecl(hasAnyName("::atoi", "::atof", "::atol", "::atoll"))
.bind("converter"),
functionDecl(hasAnyName("::scanf", "::sscanf", "::fscanf",
"::vfscanf", "::vscanf", "::vsscanf"))
.bind("formatted")))))
.bind("expr"),
this);
}
namespace {
enum class ConversionKind {
None,
ToInt,
ToUInt,
ToLongInt,
ToLongUInt,
ToIntMax,
ToUIntMax,
ToFloat,
ToDouble,
ToLongDouble
};
ConversionKind classifyConversionFunc(const FunctionDecl *FD) {
return llvm::StringSwitch<ConversionKind>(FD->getName())
.Cases("atoi", "atol", ConversionKind::ToInt)
.Case("atoll", ConversionKind::ToLongInt)
.Case("atof", ConversionKind::ToDouble)
.Default(ConversionKind::None);
}
ConversionKind classifyFormatString(StringRef Fmt, const LangOptions &LO,
const TargetInfo &TI) {
// Scan the format string for the first problematic format specifier, then
// report that as the conversion type. This will miss additional conversion
// specifiers, but that is acceptable behavior.
class Handler : public analyze_format_string::FormatStringHandler {
ConversionKind CK = ConversionKind::None;
bool HandleScanfSpecifier(const analyze_scanf::ScanfSpecifier &FS,
const char *StartSpecifier,
unsigned SpecifierLen) override {
// If we just consume the argument without assignment, we don't care
// about it having conversion errors.
if (!FS.consumesDataArgument())
return true;
// Get the conversion specifier and use it to determine the conversion
// kind.
analyze_scanf::ScanfConversionSpecifier SCS = FS.getConversionSpecifier();
if (SCS.isIntArg()) {
switch (FS.getLengthModifier().getKind()) {
case analyze_scanf::LengthModifier::AsLongLong:
CK = ConversionKind::ToLongInt;
break;
case analyze_scanf::LengthModifier::AsIntMax:
CK = ConversionKind::ToIntMax;
break;
default:
CK = ConversionKind::ToInt;
break;
}
} else if (SCS.isUIntArg()) {
switch (FS.getLengthModifier().getKind()) {
case analyze_scanf::LengthModifier::AsLongLong:
CK = ConversionKind::ToLongUInt;
break;
case analyze_scanf::LengthModifier::AsIntMax:
CK = ConversionKind::ToUIntMax;
break;
default:
CK = ConversionKind::ToUInt;
break;
}
} else if (SCS.isDoubleArg()) {
switch (FS.getLengthModifier().getKind()) {
case analyze_scanf::LengthModifier::AsLongDouble:
CK = ConversionKind::ToLongDouble;
break;
case analyze_scanf::LengthModifier::AsLong:
CK = ConversionKind::ToDouble;
break;
default:
CK = ConversionKind::ToFloat;
break;
}
}
// Continue if we have yet to find a conversion kind that we care about.
return CK == ConversionKind::None;
}
public:
Handler() = default;
ConversionKind get() const { return CK; }
};
Handler H;
analyze_format_string::ParseScanfString(H, Fmt.begin(), Fmt.end(), LO, TI);
return H.get();
}
StringRef classifyConversionType(ConversionKind K) {
switch (K) {
case ConversionKind::None:
llvm_unreachable("Unexpected conversion kind");
case ConversionKind::ToInt:
case ConversionKind::ToLongInt:
case ConversionKind::ToIntMax:
return "an integer value";
case ConversionKind::ToUInt:
case ConversionKind::ToLongUInt:
case ConversionKind::ToUIntMax:
return "an unsigned integer value";
case ConversionKind::ToFloat:
case ConversionKind::ToDouble:
case ConversionKind::ToLongDouble:
return "a floating-point value";
}
llvm_unreachable("Unknown conversion kind");
}
StringRef classifyReplacement(ConversionKind K) {
switch (K) {
case ConversionKind::None:
llvm_unreachable("Unexpected conversion kind");
case ConversionKind::ToInt:
return "strtol";
case ConversionKind::ToUInt:
return "strtoul";
case ConversionKind::ToIntMax:
return "strtoimax";
case ConversionKind::ToLongInt:
return "strtoll";
case ConversionKind::ToLongUInt:
return "strtoull";
case ConversionKind::ToUIntMax:
return "strtoumax";
case ConversionKind::ToFloat:
return "strtof";
case ConversionKind::ToDouble:
return "strtod";
case ConversionKind::ToLongDouble:
return "strtold";
}
llvm_unreachable("Unknown conversion kind");
}
} // unnamed namespace
void StrToNumCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Call = Result.Nodes.getNodeAs<CallExpr>("expr");
const FunctionDecl *FuncDecl = nullptr;
ConversionKind Conversion;
if (const auto *ConverterFunc =
Result.Nodes.getNodeAs<FunctionDecl>("converter")) {
// Converter functions are always incorrect to use.
FuncDecl = ConverterFunc;
Conversion = classifyConversionFunc(ConverterFunc);
} else if (const auto *FFD =
Result.Nodes.getNodeAs<FunctionDecl>("formatted")) {
StringRef FmtStr;
// The format string comes from the call expression and depends on which
// flavor of scanf is called.
// Index 0: scanf, vscanf, Index 1: fscanf, sscanf, vfscanf, vsscanf.
unsigned Idx =
(FFD->getName() == "scanf" || FFD->getName() == "vscanf") ? 0 : 1;
// Given the index, see if the call expression argument at that index is
// a string literal.
if (Call->getNumArgs() < Idx)
return;
if (const Expr *Arg = Call->getArg(Idx)->IgnoreParenImpCasts()) {
if (const auto *SL = dyn_cast<StringLiteral>(Arg)) {
FmtStr = SL->getString();
}
}
// If we could not get the format string, bail out.
if (FmtStr.empty())
return;
// Formatted input functions need further checking of the format string to
// determine whether a problematic conversion may be happening.
Conversion = classifyFormatString(FmtStr, getLangOpts(),
Result.Context->getTargetInfo());
if (Conversion != ConversionKind::None)
FuncDecl = FFD;
}
if (!FuncDecl)
return;
diag(Call->getExprLoc(),
"%0 used to convert a string to %1, but function will not report "
"conversion errors; consider using '%2' instead")
<< FuncDecl << classifyConversionType(Conversion)
<< classifyReplacement(Conversion);
}
} // namespace clang::tidy::cert
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