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|
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#include "plugin.hxx"
#include <cassert>
#include <string>
#include <iostream>
#include <fstream>
#include <set>
#include <stack>
/**
Look for places where we can flatten the control flow in a method by returning early.
*/
namespace {
class Flatten:
public RecursiveASTVisitor<Flatten>, public loplugin::RewritePlugin
{
public:
explicit Flatten(loplugin::InstantiationData const & data):
RewritePlugin(data) {}
virtual void run() override
{
TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
}
bool TraverseIfStmt(IfStmt *);
bool TraverseCXXCatchStmt(CXXCatchStmt * );
bool TraverseCompoundStmt(CompoundStmt *);
bool TraverseFunctionDecl(FunctionDecl *);
bool TraverseCXXMethodDecl(CXXMethodDecl *);
bool TraverseCXXConstructorDecl(CXXConstructorDecl *);
bool TraverseCXXConversionDecl(CXXConversionDecl *);
bool TraverseCXXDestructorDecl(CXXDestructorDecl *);
bool VisitIfStmt(IfStmt const * );
private:
bool rewrite1(IfStmt const * );
bool rewrite2(IfStmt const * );
bool rewriteLargeIf(IfStmt const * );
SourceRange ignoreMacroExpansions(SourceRange range);
SourceRange extendOverComments(SourceRange range);
std::string getSourceAsString(SourceRange range);
std::string invertCondition(Expr const * condExpr, SourceRange conditionRange);
bool isLargeCompoundStmt(Stmt const *);
Stmt const * lastStmtInCompoundStmt = nullptr;
FunctionDecl const * functionDecl = nullptr;
CompoundStmt const * functionDeclBody = nullptr;
Stmt const * mElseBranch = nullptr;
};
static Stmt const * containsSingleThrowExpr(Stmt const * stmt)
{
if (auto compoundStmt = dyn_cast<CompoundStmt>(stmt)) {
if (compoundStmt->size() != 1)
return nullptr;
stmt = *compoundStmt->body_begin();
}
if (auto exprWithCleanups = dyn_cast<ExprWithCleanups>(stmt)) {
stmt = exprWithCleanups->getSubExpr();
}
return dyn_cast<CXXThrowExpr>(stmt);
}
static bool containsVarDecl(Stmt const * stmt)
{
if (auto compoundStmt = dyn_cast<CompoundStmt>(stmt)) {
for (auto i = compoundStmt->body_begin(); i != compoundStmt->body_end(); ++i) {
auto declStmt = dyn_cast<DeclStmt>(*i);
if (declStmt && isa<VarDecl>(*declStmt->decl_begin()))
return true;
}
return false;
}
auto declStmt = dyn_cast<DeclStmt>(stmt);
return declStmt && isa<VarDecl>(*declStmt->decl_begin());
}
bool Flatten::TraverseCXXCatchStmt(CXXCatchStmt* )
{
// ignore stuff inside catch statements, where doing a "if...else..throw" is more natural
return true;
}
bool Flatten::TraverseIfStmt(IfStmt * ifStmt)
{
if (!WalkUpFromIfStmt(ifStmt)) {
return false;
}
auto const saved = mElseBranch;
mElseBranch = ifStmt->getElse();
auto ret = true;
for (auto const sub: ifStmt->children()) {
if (!TraverseStmt(sub)) {
ret = false;
break;
}
}
mElseBranch = saved;
return ret;
}
bool Flatten::TraverseCompoundStmt(CompoundStmt * compoundStmt)
{
auto copy = lastStmtInCompoundStmt;
if (compoundStmt->size() > 0)
lastStmtInCompoundStmt = compoundStmt->body_back();
else
lastStmtInCompoundStmt = nullptr;
bool rv = RecursiveASTVisitor<Flatten>::TraverseCompoundStmt(compoundStmt);
lastStmtInCompoundStmt = copy;
return rv;
}
bool Flatten::TraverseFunctionDecl(FunctionDecl * fd)
{
auto copy1 = functionDeclBody;
auto copy2 = fd;
functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
functionDecl = fd;
bool rv = RecursiveASTVisitor<Flatten>::TraverseFunctionDecl(fd);
functionDeclBody = copy1;
functionDecl = copy2;
return rv;
}
bool Flatten::TraverseCXXMethodDecl(CXXMethodDecl * fd)
{
auto copy1 = functionDeclBody;
auto copy2 = fd;
functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
functionDecl = fd;
bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXMethodDecl(fd);
functionDeclBody = copy1;
functionDecl = copy2;
return rv;
}
bool Flatten::TraverseCXXConstructorDecl(CXXConstructorDecl * fd)
{
auto copy1 = functionDeclBody;
auto copy2 = fd;
functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
functionDecl = fd;
bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXConstructorDecl(fd);
functionDeclBody = copy1;
functionDecl = copy2;
return rv;
}
bool Flatten::TraverseCXXConversionDecl(CXXConversionDecl * fd)
{
auto copy1 = functionDeclBody;
auto copy2 = fd;
functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
functionDecl = fd;
bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXConversionDecl(fd);
functionDeclBody = copy1;
functionDecl = copy2;
return rv;
}
bool Flatten::TraverseCXXDestructorDecl(CXXDestructorDecl * fd)
{
auto copy1 = functionDeclBody;
auto copy2 = fd;
functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
functionDecl = fd;
bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXDestructorDecl(fd);
functionDeclBody = copy1;
functionDecl = copy2;
return rv;
}
bool Flatten::VisitIfStmt(IfStmt const * ifStmt)
{
if (ignoreLocation(ifStmt))
return true;
// ignore if we are part of an if/then/else/if chain
if (ifStmt == mElseBranch || (ifStmt->getElse() && isa<IfStmt>(ifStmt->getElse())))
return true;
// look for a large if(){} block at the end of a function
if (!ifStmt->getElse()
&& (functionDecl->getReturnType().isNull() || functionDecl->getReturnType()->isVoidType())
&& functionDeclBody && functionDeclBody->size()
&& functionDeclBody->body_back() == ifStmt
&& isLargeCompoundStmt(ifStmt->getThen()))
{
if (!rewriteLargeIf(ifStmt))
{
report(
DiagnosticsEngine::Warning,
"large if statement at end of function, rather invert the condition and exit early, and flatten the function",
compat::getBeginLoc(ifStmt))
<< ifStmt->getSourceRange();
}
return true;
}
if (!ifStmt->getElse())
return true;
auto const thenThrowExpr = containsSingleThrowExpr(ifStmt->getThen());
auto const elseThrowExpr = containsSingleThrowExpr(ifStmt->getElse());
// If neither contains a throw, nothing to do; if both contain throws, no
// improvement:
if ((thenThrowExpr == nullptr) == (elseThrowExpr == nullptr)) {
return true;
}
if (containsPreprocessingConditionalInclusion(ifStmt->getSourceRange())) {
return true;
}
if (elseThrowExpr)
{
// if the "if" statement is not the last statement in its block, and it contains
// var decls in its then block, we cannot de-indent the then block without
// extending the lifetime of some variables, which may be problematic
if (ifStmt != lastStmtInCompoundStmt && containsVarDecl(ifStmt->getThen()))
return true;
if (!rewrite1(ifStmt))
{
report(
DiagnosticsEngine::Warning,
"unconditional throw in else branch, rather invert the condition, throw early, and flatten the normal case",
compat::getBeginLoc(elseThrowExpr))
<< elseThrowExpr->getSourceRange();
report(
DiagnosticsEngine::Note,
"if condition here",
compat::getBeginLoc(ifStmt))
<< ifStmt->getSourceRange();
}
}
if (thenThrowExpr)
{
// if the "if" statement is not the last statement in it's block, and it contains
// var decls in it's else block, we cannot de-indent the else block without
// extending the lifetime of some variables, which may be problematic
if (ifStmt != lastStmtInCompoundStmt && containsVarDecl(ifStmt->getElse()))
return true;
if (!rewrite2(ifStmt))
{
report(
DiagnosticsEngine::Warning,
"unconditional throw in then branch, just flatten the else",
compat::getBeginLoc(thenThrowExpr))
<< thenThrowExpr->getSourceRange();
}
}
return true;
}
static std::string stripOpenAndCloseBrace(std::string s);
static std::string stripTrailingEmptyLines(std::string s);
static std::string deindent(std::string const & s);
static std::vector<std::string> split(std::string s);
static bool startswith(std::string const & rStr, char const * pSubStr);
static int countLeadingSpaces(std::string const &);
static std::string padSpace(int iNoSpaces);
static void replace(std::string & s, std::string const & from, std::string const & to);
bool Flatten::rewrite1(IfStmt const * ifStmt)
{
if (!rewriter)
return false;
auto conditionRange = ignoreMacroExpansions(ifStmt->getCond()->getSourceRange());
if (!conditionRange.isValid()) {
return false;
}
auto thenRange = ignoreMacroExpansions(ifStmt->getThen()->getSourceRange());
if (!thenRange.isValid()) {
return false;
}
auto elseRange = ignoreMacroExpansions(ifStmt->getElse()->getSourceRange());
if (!elseRange.isValid()) {
return false;
}
SourceRange elseKeywordRange = ifStmt->getElseLoc();
thenRange = extendOverComments(thenRange);
elseRange = extendOverComments(elseRange);
elseKeywordRange = extendOverComments(elseKeywordRange);
// in adjusting the formatting I assume that "{" starts on a new line
std::string conditionString = invertCondition(ifStmt->getCond(), conditionRange);
std::string thenString = getSourceAsString(thenRange);
if (auto compoundStmt = dyn_cast<CompoundStmt>(ifStmt->getThen())) {
if (compoundStmt->getLBracLoc().isValid()) {
thenString = stripOpenAndCloseBrace(thenString);
}
}
thenString = deindent(thenString);
std::string elseString = getSourceAsString(elseRange);
if (!replaceText(elseRange, thenString)) {
return false;
}
if (!removeText(elseKeywordRange)) {
return false;
}
if (!replaceText(thenRange, elseString)) {
return false;
}
if (!replaceText(conditionRange, conditionString)) {
return false;
}
return true;
}
bool Flatten::rewrite2(IfStmt const * ifStmt)
{
if (!rewriter)
return false;
auto conditionRange = ignoreMacroExpansions(ifStmt->getCond()->getSourceRange());
if (!conditionRange.isValid()) {
return false;
}
auto thenRange = ignoreMacroExpansions(ifStmt->getThen()->getSourceRange());
if (!thenRange.isValid()) {
return false;
}
auto elseRange = ignoreMacroExpansions(ifStmt->getElse()->getSourceRange());
if (!elseRange.isValid()) {
return false;
}
SourceRange elseKeywordRange = ifStmt->getElseLoc();
elseRange = extendOverComments(elseRange);
elseKeywordRange = extendOverComments(elseKeywordRange);
// in adjusting the formatting I assume that "{" starts on a new line
std::string elseString = getSourceAsString(elseRange);
if (auto compoundStmt = dyn_cast<CompoundStmt>(ifStmt->getElse())) {
if (compoundStmt->getLBracLoc().isValid()) {
elseString = stripOpenAndCloseBrace(elseString);
}
}
elseString = deindent(elseString);
if (!replaceText(elseRange, elseString)) {
return false;
}
if (!removeText(elseKeywordRange)) {
return false;
}
return true;
}
bool Flatten::rewriteLargeIf(IfStmt const * ifStmt)
{
if (!rewriter)
return false;
auto conditionRange = ignoreMacroExpansions(ifStmt->getCond()->getSourceRange());
if (!conditionRange.isValid()) {
return false;
}
auto thenRange = ignoreMacroExpansions(ifStmt->getThen()->getSourceRange());
if (!thenRange.isValid()) {
return false;
}
thenRange = extendOverComments(thenRange);
// in adjusting the formatting I assume that "{" starts on a new line
std::string conditionString = invertCondition(ifStmt->getCond(), conditionRange);
std::string thenString = getSourceAsString(thenRange);
if (auto compoundStmt = dyn_cast<CompoundStmt>(ifStmt->getThen())) {
if (compoundStmt->getLBracLoc().isValid()) {
thenString = stripOpenAndCloseBrace(thenString);
}
}
int iNoSpaces = countLeadingSpaces(thenString);
thenString = padSpace(iNoSpaces) + "return;\n\n" + deindent(thenString);
thenString = stripTrailingEmptyLines(thenString);
if (!replaceText(thenRange, thenString)) {
return false;
}
if (!replaceText(conditionRange, conditionString)) {
return false;
}
return true;
}
std::string Flatten::invertCondition(Expr const * condExpr, SourceRange conditionRange)
{
std::string s = getSourceAsString(conditionRange);
condExpr = condExpr->IgnoreImpCasts();
if (auto exprWithCleanups = dyn_cast<ExprWithCleanups>(condExpr))
condExpr = exprWithCleanups->getSubExpr()->IgnoreImpCasts();
// an if statement will automatically invoke a bool-conversion method
if (auto memberCallExpr = dyn_cast<CXXMemberCallExpr>(condExpr))
{
if (isa<CXXConversionDecl>(memberCallExpr->getMethodDecl()))
condExpr = memberCallExpr->getImplicitObjectArgument()->IgnoreImpCasts();
}
if (auto unaryOp = dyn_cast<UnaryOperator>(condExpr))
{
if (unaryOp->getOpcode() != UO_LNot)
return "!(" + s + ")";
auto i = s.find("!");
assert (i != std::string::npos);
s = s.substr(i+1);
}
else if (auto binaryOp = dyn_cast<BinaryOperator>(condExpr))
{
switch (binaryOp->getOpcode())
{
case BO_LT: replace(s, "<", ">="); break;
case BO_GT: replace(s, ">", "<="); break;
case BO_LE: replace(s, "<=", ">"); break;
case BO_GE: replace(s, ">=", "<"); break;
case BO_EQ: replace(s, "==", "!="); break;
case BO_NE: replace(s, "!=", "=="); break;
default:
s = "!(" + s + ")";
}
}
else if (auto opCallExpr = dyn_cast<CXXOperatorCallExpr>(condExpr))
{
switch (opCallExpr->getOperator())
{
case OO_Less: replace(s, "<", ">="); break;
case OO_Greater: replace(s, ">", "<="); break;
case OO_LessEqual: replace(s, "<=", ">"); break;
case OO_GreaterEqual: replace(s, ">=", "<"); break;
case OO_EqualEqual: replace(s, "==", "!="); break;
case OO_ExclaimEqual: replace(s, "!=", "=="); break;
default:
s = "!(" + s + ")";
}
}
else if (isa<DeclRefExpr>(condExpr) || isa<CallExpr>(condExpr) || isa<MemberExpr>(condExpr))
s = "!" + s;
else
s = "!(" + s + ")";
return s;
}
std::string stripOpenAndCloseBrace(std::string s)
{
size_t i = s.find("{");
if (i == std::string::npos)
throw "did not find {";
++i;
// strip to line end
while (s[i] == ' ')
++i;
if (s[i] == '\n')
++i;
s = s.substr(i);
i = s.rfind("}");
if (i == std::string::npos)
throw "did not find }";
--i;
while (s[i] == ' ')
--i;
s = s.substr(0,i);
return s;
}
std::string deindent(std::string const & s)
{
std::vector<std::string> lines = split(s);
std::string rv;
for (auto s : lines) {
if (startswith(s, " "))
rv += s.substr(4);
else
rv += s;
rv += "\n";
}
return rv;
}
std::vector<std::string> split(std::string s)
{
if (s.back() == '\n')
s = s.substr(0, s.size()-1);
size_t next = -1;
std::vector<std::string> rv;
do
{
size_t current = next + 1;
next = s.find_first_of( "\n", current );
rv.push_back(s.substr( current, next - current ));
}
while (next != std::string::npos);
return rv;
}
bool startswith(std::string const & rStr, char const * pSubStr)
{
return rStr.compare(0, strlen(pSubStr), pSubStr) == 0;
}
int countLeadingSpaces(std::string const & s)
{
int i = 0;
while (i < (int)s.length() && s[i] == ' ')
i++;
return i;
}
std::string padSpace(int iNoSpaces)
{
std::string s;
for (int i = 0; i < iNoSpaces; ++i)
s += " ";
return s;
}
std::string stripTrailingEmptyLines(std::string s)
{
while (s.back() == '\n')
s.resize(s.length() - 1);
return s;
}
void replace(std::string & s, std::string const & from, std::string const & to)
{
auto i = s.find(from);
assert (i != std::string::npos);
s.replace(i, from.length(), to);
// just in case we have something really weird, like the operator token is also present in the rest of the condition somehow
assert (s.find(from) == std::string::npos);
}
SourceRange Flatten::ignoreMacroExpansions(SourceRange range) {
while (compiler.getSourceManager().isMacroArgExpansion(range.getBegin())) {
range.setBegin(
compiler.getSourceManager().getImmediateMacroCallerLoc(
range.getBegin()));
}
if (range.getBegin().isMacroID()) {
SourceLocation loc;
if (Lexer::isAtStartOfMacroExpansion(
range.getBegin(), compiler.getSourceManager(),
compiler.getLangOpts(), &loc))
{
range.setBegin(loc);
}
}
while (compiler.getSourceManager().isMacroArgExpansion(range.getEnd())) {
range.setEnd(
compiler.getSourceManager().getImmediateMacroCallerLoc(
range.getEnd()));
}
if (range.getEnd().isMacroID()) {
SourceLocation loc;
if (Lexer::isAtEndOfMacroExpansion(
range.getEnd(), compiler.getSourceManager(),
compiler.getLangOpts(), &loc))
{
range.setEnd(loc);
}
}
return range.getBegin().isMacroID() || range.getEnd().isMacroID()
? SourceRange() : range;
}
/**
* Extend the SourceRange to include any leading and trailing whitespace, and any comments.
*/
SourceRange Flatten::extendOverComments(SourceRange range)
{
SourceManager& SM = compiler.getSourceManager();
SourceLocation startLoc = range.getBegin();
SourceLocation endLoc = range.getEnd();
char const *p1 = SM.getCharacterData( startLoc );
char const *p2 = SM.getCharacterData( endLoc );
// scan backwards from the beginning to include any spaces on that line
while (*(p1-1) == ' ')
--p1;
startLoc = startLoc.getLocWithOffset(p1 - SM.getCharacterData( startLoc ));
// look for trailing ";"
while (*(p2+1) == ';')
++p2;
// look for trailing " "
while (*(p2+1) == ' ')
++p2;
// look for single line comments attached to the end of the statement
if (*(p2+1) == '/' && *(p2+2) == '/')
{
p2 += 2;
while (*(p2+1) && *(p2+1) != '\n')
++p2;
if (*(p2+1) == '\n')
++p2;
}
else
{
// make the source code we extract include any trailing "\n"
if (*(p2+1) == '\n')
++p2;
}
endLoc = endLoc.getLocWithOffset(p2 - SM.getCharacterData( endLoc ));
return SourceRange(startLoc, endLoc);
}
std::string Flatten::getSourceAsString(SourceRange range)
{
SourceManager& SM = compiler.getSourceManager();
SourceLocation startLoc = range.getBegin();
SourceLocation endLoc = range.getEnd();
char const *p1 = SM.getCharacterData( startLoc );
char const *p2 = SM.getCharacterData( endLoc );
p2 += Lexer::MeasureTokenLength( endLoc, SM, compiler.getLangOpts());
return std::string( p1, p2 - p1);
}
bool Flatten::isLargeCompoundStmt(Stmt const * stmt)
{
auto stmtRange = stmt->getSourceRange();
std::string s = getSourceAsString(stmtRange);
return std::count(s.begin(), s.end(), '\n') > 10;
}
loplugin::Plugin::Registration< Flatten > X("flatten", false);
}
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