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llvm-github/clang/test/Analysis/lifetime-extension.cpp
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lifetime-extension.cpp
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// RUN: %clang_analyze_cc1 -Wno-unused -std=c++11 -analyzer-checker=core,debug.ExprInspection -verify %s
// RUN: %clang_analyze_cc1 -Wno-unused -std=c++11 -analyzer-checker=core,debug.ExprInspection -analyzer-config cfg-temporary-dtors=true -DTEMPORARIES -verify %s
void clang_analyzer_eval(bool);
namespace pr17001_call_wrong_destructor {
bool x;
struct A {
int *a;
A() {}
~A() {}
};
struct B : public A {
B() {}
~B() { x = true; }
};
void f() {
{
const A &a = B();
}
clang_analyzer_eval(x); // expected-warning{{TRUE}}
}
} // end namespace pr17001_call_wrong_destructor
namespace pr19539_crash_on_destroying_an_integer {
struct A {
int i;
int j[2];
A() : i(1) {
j[0] = 2;
j[1] = 3;
}
~A() {}
};
void f() {
const int &x = A().i; // no-crash
const int &y = A().j[1]; // no-crash
const int &z = (A().j[1], A().j[0]); // no-crash
clang_analyzer_eval(x == 1);
clang_analyzer_eval(y == 3);
clang_analyzer_eval(z == 2);
#ifdef TEMPORARIES
// expected-warning@-4{{TRUE}}
// expected-warning@-4{{TRUE}}
// expected-warning@-4{{TRUE}}
#else
// expected-warning@-8{{UNKNOWN}}
// expected-warning@-8{{UNKNOWN}}
// expected-warning@-8{{UNKNOWN}}
#endif
}
} // end namespace pr19539_crash_on_destroying_an_integer
namespace maintain_original_object_address_on_lifetime_extension {
class C {
C **after, **before;
public:
bool x;
C(bool x, C **after, C **before) : x(x), after(after), before(before) {
*before = this;
}
// Don't track copies in our tests.
C(const C &c) : x(c.x), after(nullptr), before(nullptr) {}
~C() { if (after) *after = this; }
operator bool() const { return x; }
};
void f1() {
C *after, *before;
{
const C &c = C(true, &after, &before);
}
clang_analyzer_eval(after == before);
#ifdef TEMPORARIES
// expected-warning@-2{{TRUE}}
#else
// expected-warning@-4{{UNKNOWN}}
#endif
}
void f2() {
C *after, *before;
C c = C(1, &after, &before);
clang_analyzer_eval(after == before);
#ifdef TEMPORARIES
// expected-warning@-2{{TRUE}}
#else
// expected-warning@-4{{UNKNOWN}}
#endif
}
void f3(bool coin) {
C *after, *before;
{
const C &c = coin ? C(true, &after, &before) : C(false, &after, &before);
}
clang_analyzer_eval(after == before);
#ifdef TEMPORARIES
// expected-warning@-2{{TRUE}}
#else
// expected-warning@-4{{UNKNOWN}}
#endif
}
void f4(bool coin) {
C *after, *before;
{
// no-crash
const C &c = C(coin, &after, &before) ?: C(false, &after, &before);
}
// FIXME: Add support for lifetime extension through binary conditional
// operator. Ideally also add support for the binary conditional operator in
// C++. Because for now it calls the constructor for the condition twice.
if (coin) {
clang_analyzer_eval(after == before);
#ifdef TEMPORARIES
// expected-warning@-2{{The left operand of '==' is a garbage value}}
#else
// expected-warning@-4{{UNKNOWN}}
#endif
} else {
clang_analyzer_eval(after == before);
#ifdef TEMPORARIES
// Seems to work at the moment, but also seems accidental.
// Feel free to break.
// expected-warning@-4{{TRUE}}
#else
// expected-warning@-6{{UNKNOWN}}
#endif
}
}
void f5() {
C *after, *before;
{
const bool &x = C(true, &after, &before).x; // no-crash
}
// FIXME: Should be TRUE. Should not warn about garbage value.
clang_analyzer_eval(after == before);
#ifdef TEMPORARIES
// expected-warning@-2{{The left operand of '==' is a garbage value}}
#else
// expected-warning@-4{{UNKNOWN}}
#endif
}
} // end namespace maintain_original_object_address_on_lifetime_extension
namespace maintain_original_object_address_on_move {
class C {
int *x;
public:
C() : x(nullptr) {}
C(int *x) : x(x) {}
C(const C &c) = delete;
C(C &&c) : x(c.x) { c.x = nullptr; }
C &operator=(C &&c) {
x = c.x;
c.x = nullptr;
return *this;
}
~C() {
// This was triggering the division by zero warning in f1() and f2():
// Because move-elision materialization was incorrectly causing the object
// to be relocated from one address to another before move, but destructor
// was operating on the old address, it was still thinking that 'x' is set.
if (x)
*x = 0;
}
};
void f1() {
int x = 1;
// &x is replaced with nullptr in move-constructor before the temporary dies.
C c = C(&x);
// Hence x was not set to 0 yet.
1 / x; // no-warning
}
void f2() {
int x = 1;
C c;
// &x is replaced with nullptr in move-assignment before the temporary dies.
c = C(&x);
// Hence x was not set to 0 yet.
1 / x; // no-warning
}
} // end namespace maintain_original_object_address_on_move

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