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Improve propogation of lifetimes of function arguments 

This will now warn for cases like this:

```cpp
int* f(int * x) {
    return x;
}
int * g(int x) {
    return f(&x);
}
````
This commit is contained in:
Paul Fultz II 2019-07-26 07:02:07 +02:00 committed by Daniel Marjamäki
parent fbd7b5180b
commit b049fd9303
2 changed files with 57 additions and 19 deletions
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59
lib/valueflow.cpp
View File

@ -3034,14 +3034,43 @@ struct LifetimeStore {
ValueFlow::Value::LifetimeKind type;
ErrorPath errorPath;
LifetimeStore()
: argtok(nullptr), message(), type(), errorPath()
{}
LifetimeStore(const Token *argtok,
const std::string &message,
ValueFlow::Value::LifetimeKind type = ValueFlow::Value::LifetimeKind::Object)
: argtok(argtok), message(message), type(type), errorPath()
{}
static LifetimeStore fromFunctionArg(const Function * f, Token *tok, const Variable *var, TokenList *tokenlist, ErrorLogger *errorLogger) {
if (!var)
return LifetimeStore{};
if (!var->isArgument())
return LifetimeStore{};
int n = getArgumentPos(var, f);
if (n < 0)
return LifetimeStore{};
std::vector<const Token *> args = getArguments(tok);
if (n >= args.size()) {
if (tokenlist->getSettings()->debugwarnings)
bailout(tokenlist,
errorLogger,
tok,
"Argument mismatch: Function '" + tok->str() + "' returning lifetime from argument index " +
std::to_string(n) + " but only " + std::to_string(args.size()) +
" arguments are available.");
return LifetimeStore{};
}
const Token *argtok2 = args[n];
return LifetimeStore{argtok2, "Passed to '" + tok->str() + "'.", ValueFlow::Value::LifetimeKind::Object};
}
template <class Predicate>
void byRef(Token *tok, TokenList *tokenlist, ErrorLogger *errorLogger, const Settings *settings, Predicate pred) const {
if (!argtok)
return;
ErrorPath er = errorPath;
const Token *lifeTok = getLifetimeToken(argtok, er);
if (!lifeTok)
@ -3071,6 +3100,8 @@ struct LifetimeStore {
template <class Predicate>
void byVal(Token *tok, TokenList *tokenlist, ErrorLogger *errorLogger, const Settings *settings, Predicate pred) const {
if (!argtok)
return;
if (argtok->values().empty()) {
ErrorPath er;
er.emplace_back(argtok, message);
@ -3124,6 +3155,8 @@ struct LifetimeStore {
template <class Predicate>
void byDerefCopy(Token *tok, TokenList *tokenlist, ErrorLogger *errorLogger, const Settings *settings, Predicate pred) const {
if (!argtok)
return;
for (const ValueFlow::Value &v : argtok->values()) {
if (!v.isLifetimeValue())
continue;
@ -3184,32 +3217,20 @@ static void valueFlowLifetimeFunction(Token *tok, TokenList *tokenlist, ErrorLog
const Token *returnTok = findSimpleReturn(f);
if (!returnTok)
return;
const Variable *returnVar = returnTok->variable();
if (returnVar && returnVar->isArgument() && (returnVar->isConst() || !isVariableChanged(returnVar, settings, tokenlist->isCPP()))) {
LifetimeStore ls = LifetimeStore::fromFunctionArg(f, tok, returnVar, tokenlist, errorLogger);
ls.byVal(tok->next(), tokenlist, errorLogger, settings);
}
for (const ValueFlow::Value &v : returnTok->values()) {
if (!v.isLifetimeValue())
continue;
if (!v.tokvalue)
continue;
const Variable *var = v.tokvalue->variable();
if (!var)
LifetimeStore ls = LifetimeStore::fromFunctionArg(f, tok, var, tokenlist, errorLogger);
if (!ls.argtok)
continue;
if (!var->isArgument())
continue;
int n = getArgumentPos(var, f);
if (n < 0)
continue;
std::vector<const Token *> args = getArguments(tok);
if (n >= args.size()) {
if (tokenlist->getSettings()->debugwarnings)
bailout(tokenlist,
errorLogger,
tok,
"Argument mismatch: Function '" + tok->str() + "' returning lifetime from argument index " +
std::to_string(n) + " but only " + std::to_string(args.size()) +
" arguments are available.");
continue;
}
const Token *argtok = args[n];
LifetimeStore ls{argtok, "Passed to '" + tok->str() + "'.", ValueFlow::Value::LifetimeKind::Object};
ls.errorPath = v.errorPath;
ls.errorPath.emplace_front(returnTok, "Return " + lifetimeType(returnTok, &v) + ".");
if (var->isReference() || var->isRValueReference()) {

17
test/testautovariables.cpp
View File

@ -1161,6 +1161,23 @@ private:
"[test.cpp:1] -> [test.cpp:2] -> [test.cpp:6] -> [test.cpp:6] -> [test.cpp:5] -> [test.cpp:6]: (error) Returning pointer to local variable 'x' that will be invalid when returning.\n",
errout.str());
check("int* f(int * x) {\n"
" return x;\n"
"}\n"
"int * g(int x) {\n"
" return f(&x);\n"
"}\n");
ASSERT_EQUALS("[test.cpp:5] -> [test.cpp:5] -> [test.cpp:4] -> [test.cpp:5]: (error) Returning pointer to local variable 'x' that will be invalid when returning.\n", errout.str());
check("int* f(int * x) {\n"
" x = nullptr;\n"
" return x;\n"
"}\n"
"int * g(int x) {\n"
" return f(&x);\n"
"}\n");
ASSERT_EQUALS("", errout.str());
check("int f(int& a) {\n"
" return a;\n"
"}\n"