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llvm-project/clang/test/Analysis/inner-pointer.cpp
Richard Smith b27430f9f4 Treat std::move, forward, etc. as builtins. 
This is extended to all `std::` functions that take a reference to a
value and return a reference (or pointer) to that same value: `move`,
`forward`, `move_if_noexcept`, `as_const`, `addressof`, and the
libstdc++-specific function `__addressof`.

We still require these functions to be declared before they can be used,
but don't instantiate their definitions unless their addresses are
taken. Instead, code generation, constant evaluation, and static
analysis are given direct knowledge of their effect.

This change aims to reduce various costs associated with these functions
-- per-instantiation memory costs, compile time and memory costs due to
creating out-of-line copies and inlining them, code size at -O0, and so
on -- so that they are not substantially more expensive than a cast.
Most of these improvements are very small, but I measured a 3% decrease
in -O0 object file size for a simple C++ source file using the standard
library after this change.

We now automatically infer the `const` and `nothrow` attributes on these
now-builtin functions, in particular meaning that we get a warning for
an unused call to one of these functions.

In C++20 onwards, we disallow taking the addresses of these functions,
per the C++20 "addressable function" rule. In earlier language modes, a
compatibility warning is produced but the address can still be taken.

The same infrastructure is extended to the existing MSVC builtin
`__GetExceptionInfo`, which is now only recognized in namespace `std`
like it always should have been.

This is a re-commit of
  fc3090109643af8d2da9822d0f99c84742b9c877,
  a571f82a50416b767fd3cce0fb5027bb5dfec58c, and
  64c045e25b8471bbb572bd29159c294a82a86a25
which were reverted in
  e75d8b70370435b0ad10388afba0df45fcf9bfcc
due to a crasher bug where CodeGen would emit a builtin glvalue as an
rvalue if it constant-folds.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D123345
2022-04-17 13:26:16 -07:00

429 lines
17 KiB
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// RUN: %clang_analyze_cc1 -std=c++14 -analyzer-checker=cplusplus.InnerPointer \
// RUN: -Wno-dangling -Wno-dangling-field -Wno-return-stack-address \
// RUN: %s -analyzer-output=text -verify
#include "Inputs/system-header-simulator-cxx.h"
namespace std {
template <typename T>
void func_ref(T &a);
template <typename T>
void func_const_ref(const T &a);
template <typename T>
void func_value(T a);
string my_string = "default";
void default_arg(int a = 42, string &b = my_string);
template <class T>
T *addressof(T &arg);
char *data(std::string &c);
} // end namespace std
void consume(const char *) {}
void consume(const wchar_t *) {}
void consume(const char16_t *) {}
void consume(const char32_t *) {}
//=--------------------------------------=//
// `std::string` member functions //
//=--------------------------------------=//
void deref_after_scope_char(bool cond) {
const char *c, *d;
{
std::string s;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
d = s.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
} // expected-note {{Inner buffer of 'std::string' deallocated by call to destructor}}
// expected-note@-1 {{Inner buffer of 'std::string' deallocated by call to destructor}}
std::string s;
const char *c2 = s.c_str();
if (cond) {
// expected-note@-1 {{Assuming 'cond' is true}}
// expected-note@-2 {{Taking true branch}}
// expected-note@-3 {{Assuming 'cond' is false}}
// expected-note@-4 {{Taking false branch}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
} else {
consume(d); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
}
void deref_after_scope_char_data_non_const() {
char *c;
{
std::string s;
c = s.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
} // expected-note {{Inner buffer of 'std::string' deallocated by call to destructor}}
std::string s;
char *c2 = s.data();
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_scope_wchar_t(bool cond) {
const wchar_t *c, *d;
{
std::wstring s;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::wstring' obtained here}}
d = s.data(); // expected-note {{Pointer to inner buffer of 'std::wstring' obtained here}}
} // expected-note {{Inner buffer of 'std::wstring' deallocated by call to destructor}}
// expected-note@-1 {{Inner buffer of 'std::wstring' deallocated by call to destructor}}
std::wstring s;
const wchar_t *c2 = s.c_str();
if (cond) {
// expected-note@-1 {{Assuming 'cond' is true}}
// expected-note@-2 {{Taking true branch}}
// expected-note@-3 {{Assuming 'cond' is false}}
// expected-note@-4 {{Taking false branch}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
} else {
consume(d); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
}
void deref_after_scope_char16_t_cstr() {
const char16_t *c16;
{
std::u16string s16;
c16 = s16.c_str(); // expected-note {{Pointer to inner buffer of 'std::u16string' obtained here}}
} // expected-note {{Inner buffer of 'std::u16string' deallocated by call to destructor}}
std::u16string s16;
const char16_t *c16_2 = s16.c_str();
consume(c16); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_scope_char32_t_data() {
const char32_t *c32;
{
std::u32string s32;
c32 = s32.data(); // expected-note {{Pointer to inner buffer of 'std::u32string' obtained here}}
} // expected-note {{Inner buffer of 'std::u32string' deallocated by call to destructor}}
std::u32string s32;
const char32_t *c32_2 = s32.data();
consume(c32); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void multiple_symbols(bool cond) {
const char *c1, *d1;
{
std::string s1;
c1 = s1.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
d1 = s1.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
const char *local = s1.c_str();
consume(local); // no-warning
} // expected-note {{Inner buffer of 'std::string' deallocated by call to destructor}}
// expected-note@-1 {{Inner buffer of 'std::string' deallocated by call to destructor}}
std::string s2;
const char *c2 = s2.c_str();
if (cond) {
// expected-note@-1 {{Assuming 'cond' is true}}
// expected-note@-2 {{Taking true branch}}
// expected-note@-3 {{Assuming 'cond' is false}}
// expected-note@-4 {{Taking false branch}}
consume(c1); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
} else {
consume(d1); // expected-warning {{Inner pointer of container used after re/deallocation}}
} // expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_scope_ok(bool cond) {
const char *c, *d;
std::string s;
{
c = s.c_str();
d = s.data();
}
if (cond)
consume(c); // no-warning
else
consume(d); // no-warning
}
void deref_after_equals() {
const char *c;
std::string s = "hello";
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s = "world"; // expected-note {{Inner buffer of 'std::string' reallocated by call to 'operator='}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_plus_equals() {
const char *c;
std::string s = "hello";
c = s.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s += " world"; // expected-note {{Inner buffer of 'std::string' reallocated by call to 'operator+='}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_clear() {
const char *c;
std::string s;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.clear(); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'clear'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_append() {
const char *c;
std::string s = "hello";
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.append(2, 'x'); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'append'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_assign() {
const char *c;
std::string s;
c = s.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.assign(4, 'a'); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'assign'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_erase() {
const char *c;
std::string s = "hello";
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.erase(0, 2); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'erase'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_insert() {
const char *c;
std::string s = "ello";
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.insert(0, 1, 'h'); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'insert'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_replace() {
const char *c;
std::string s = "hello world";
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.replace(6, 5, "string"); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'replace'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_pop_back() {
const char *c;
std::string s;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.pop_back(); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'pop_back'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_push_back() {
const char *c;
std::string s;
c = s.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.push_back('c'); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'push_back'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_reserve() {
const char *c;
std::string s;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.reserve(5); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'reserve'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_resize() {
const char *c;
std::string s;
c = s.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.resize(5); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'resize'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_shrink_to_fit() {
const char *c;
std::string s;
c = s.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.shrink_to_fit(); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'shrink_to_fit'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_swap() {
const char *c;
std::string s1, s2;
c = s1.data(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s1.swap(s2); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'swap'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void deref_after_std_data() {
const char *c;
std::string s;
c = std::data(s); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
s.push_back('c'); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'push_back'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
struct S {
std::string s;
const char *name() {
return s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
// expected-note@-1 {{Pointer to inner buffer of 'std::string' obtained here}}
}
void clear() {
s.clear(); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'clear'}}
}
~S() {} // expected-note {{Inner buffer of 'std::string' deallocated by call to destructor}}
};
void cleared_through_method() {
S x;
const char *c = x.name(); // expected-note {{Calling 'S::name'}}
// expected-note@-1 {{Returning from 'S::name'}}
x.clear(); // expected-note {{Calling 'S::clear'}}
// expected-note@-1 {{Returning; inner buffer was reallocated}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void destroyed_through_method() {
S y;
const char *c = y.name(); // expected-note {{Calling 'S::name'}}
// expected-note@-1 {{Returning from 'S::name'}}
y.~S(); // expected-note {{Calling '~S'}}
// expected-note@-1 {{Returning; inner buffer was deallocated}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
//=---------------------------=//
// Other STL functions //
//=---------------------------=//
void STL_func_ref() {
const char *c;
std::string s;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
std::func_ref(s); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'func_ref'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void STL_func_const_ref() {
const char *c;
std::string s;
c = s.c_str();
std::func_const_ref(s);
consume(c); // no-warning
}
void STL_func_value() {
const char *c;
std::string s;
c = s.c_str();
std::func_value(s);
consume(c); // no-warning
}
void func_ptr_known() {
const char *c;
std::string s;
void (*func_ptr)(std::string &) = std::func_ref<std::string>;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
func_ptr(s); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'func_ref'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void func_ptr_unknown(void (*func_ptr)(std::string &)) {
const char *c;
std::string s;
c = s.c_str();
func_ptr(s);
consume(c); // no-warning
}
void func_default_arg() {
const char *c;
std::string s;
c = s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
default_arg(3, s); // expected-note {{Inner buffer of 'std::string' reallocated by call to 'default_arg'}}
consume(c); // expected-warning {{Inner pointer of container used after re/deallocation}}
// expected-note@-1 {{Inner pointer of container used after re/deallocation}}
}
void func_addressof() {
const char *c;
std::string s;
c = s.c_str();
(void)addressof(s);
consume(c); // no-warning
}
void func_std_data() {
const char *c;
std::string s;
c = std::data(s);
consume(c); // no-warning
}
struct T {
std::string to_string() { return s; }
private:
std::string s;
};
const char *escape_via_return_temp() {
T x;
return x.to_string().c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
// expected-note@-1 {{Inner buffer of 'std::string' deallocated by call to destructor}}
// expected-warning@-2 {{Inner pointer of container used after re/deallocation}}
// expected-note@-3 {{Inner pointer of container used after re/deallocation}}
}
const char *escape_via_return_local() {
std::string s;
return s.c_str(); // expected-note {{Pointer to inner buffer of 'std::string' obtained here}}
// expected-note@-1 {{Inner buffer of 'std::string' deallocated by call to destructor}}
// expected-warning@-2 {{Inner pointer of container used after re/deallocation}}
// expected-note@-3 {{Inner pointer of container used after re/deallocation}}
}
char *c();
class A {};
void no_CXXRecordDecl() {
A a, *b;
*(void **)&b = c() + 1;
*b = a; // no-crash
}
void checkReference(std::string &s) {
const char *c = s.c_str();
}
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