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Draft: Fix deferred init narrowing #1446 #1449

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33 changes: 33 additions & 0 deletions include/cpp2util.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1488,11 +1488,15 @@ class deferred_init {
auto destroy() -> void { if (init) { t().~T(); } init = false; }

public:
using value_type = T;

constexpr deferred_init() noexcept { }
constexpr ~deferred_init() noexcept { destroy(); }
constexpr auto value() noexcept -> T& { cpp2_default.enforce(init); return t(); }

constexpr auto construct(auto&& ...args) -> void { cpp2_default.enforce(!init); new (&data) T{CPP2_FORWARD(args)...}; init = true; }

constexpr auto construct_from(auto&& factory) -> void { cpp2_default.enforce(!init); new (&data) T(CPP2_FORWARD(factory)()); init = true; }
};


Expand All @@ -1512,6 +1516,8 @@ class out {
bool called_construct_ = false;

public:
using value_type = T;

constexpr out(T* t_) noexcept : t{ t_}, has_t{true} { cpp2_default.enforce( t); }
constexpr out(deferred_init<T>* dt_) noexcept : dt{dt_}, has_t{false} { cpp2_default.enforce(dt); }
constexpr out(out<T>* ot_) noexcept : ot{ot_}, has_t{ot_->has_t} { cpp2_default.enforce(ot);
Expand Down Expand Up @@ -1561,6 +1567,33 @@ class out {
}
}

constexpr auto construct_from(auto&& factory) -> void {
if (has_t || called_construct()) {
if constexpr (requires { *t = CPP2_FORWARD(factory)(); }) {
cpp2_default.enforce( t );
*t = CPP2_FORWARD(factory)();
}
else {
cpp2_default.report_violation("attempted to copy assign, but copy assignment is not available");
}
}
else {
cpp2_default.enforce( dt );
if (dt->init) {
if constexpr (requires { dt->value() = CPP2_FORWARD(factory)(); }) {
dt->value() = CPP2_FORWARD(factory)();
}
else {
cpp2_default.report_violation("attempted to copy assign, but copy assignment is not available");
}
}
else {
dt->construct_from(CPP2_FORWARD(factory));
called_construct() = true;
}
}
}

constexpr auto value() noexcept -> T& {
if (has_t) {
cpp2_default.enforce( t );
Expand Down
52 changes: 52 additions & 0 deletions regression-tests/mixed-bugfix-for-deferred-init-narrowing-aggregates.cpp2
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@@ -0,0 +1,52 @@
#include <cstdint>

struct S {
std::int8_t x;
std::int8_t y;
};

struct Nested {
S left;
S right;
};

inline constexpr std::int16_t constexpr_i16 = 100;
inline constexpr std::int8_t constexpr_i8 = 8;

main: () -> int = {
runtime_i8: i8 = 8;

s_good0: S = (constexpr_i16, runtime_i8);
s_good: S;
s_good = (constexpr_i16, runtime_i8);

s_reverse0: S = (runtime_i8, constexpr_i16);
s_reverse: S;
s_reverse = (runtime_i8, constexpr_i16);

s_constexpr0: S = (constexpr_i16, constexpr_i16);
s_constexpr: S;
s_constexpr = (constexpr_i16, constexpr_i16);

s_runtime0: S = (runtime_i8, runtime_i8);
s_runtime: S;
s_runtime = (runtime_i8, runtime_i8);

nested0: Nested = (
:S = (constexpr_i16, runtime_i8),
:S = (constexpr_i8, runtime_i8)
);
nested: Nested;
nested = (
:S = (constexpr_i16, runtime_i8),
:S = (constexpr_i8, runtime_i8)
);

assert(s_good0.x == 100 && s_good.y == 8);
assert(s_reverse0.x == 8 && s_reverse.y == 100);
assert(s_constexpr0.x == 100 && s_constexpr.y == 100);
assert(s_runtime0.x == 8 && s_runtime.y == 8);
assert(nested0.left.x == 100 && nested.right.y == 8);

return 0;
}
31 changes: 31 additions & 0 deletions regression-tests/pure2-bugfix-for-deferred-init-narrowing-constexpr.cpp2
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@@ -0,0 +1,31 @@
value: i32 == 20;

foo: () -> i32 == 20;

add: (x: i32, y: i32) -> i32 == x + y;

main: () -> int = {
a0: i8 = value + 100;
a: i8;
a = value + 100;

b0: i8 = foo() + 100;
b: i8;
b = foo() + 100;

c0: i16 = add(value, foo()) + 100;
c: i16;
c = add(value, foo()) + 100;

local: i32 == 10;

d0: i16 = add(local, foo()) * 2 + value;
d: i16;
d = add(local, foo()) * 2 + value;

e0: std::array<i8, 3> = (value + 100, foo() + 100, add(local, foo()));
e: std::array<i8, 3>;
e = (value + 100, foo() + 100, add(local, foo()));

return 0;
}
27 changes: 27 additions & 0 deletions regression-tests/pure2-bugfix-for-deferred-init-narrowing-literals.cpp2
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@@ -0,0 +1,27 @@
main: () -> int = {
a0: u8 = 'a';
a: u8;
a = 'a';

b0: i8 = 1;
b: i8;
b = 1;

c0: u8 = 2;
c: u8;
c = 2;

d0: i16 = 3;
d: i16;
d = 3;

e0: u16 = 4;
e: u16;
e = 4;

f0: std::array<i8, 3> = (5, 6, 7);
f: std::array<i8, 3>;
f = (5, 6, 7);

return 0;
}
54 changes: 54 additions & 0 deletions regression-tests/pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2
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@@ -0,0 +1,54 @@
// Target type is {i8, i8}. We try every pair from:
// ce_i8, ce_i16, rt_i8, rt_i16
// = 4 x 4 = 16 combinations.
//
// Constexpr sources must appear by name in the initializer, otherwise they
// stop being constant expressions and every i16 case would fail.

ce_i8: i8 == 8;
ce_i16: i16 == 8;

try_all_combinations: (rt_i8: i8, rt_i16: i16) = {
a00: std::array<i8, 2>;
a00 = (ce_i8, ce_i8);
a01: std::array<i8, 2>;
a01 = (ce_i8, ce_i16);
a02: std::array<i8, 2>;
a02 = (ce_i8, rt_i8);
a03: std::array<i8, 2>;
a03 = (ce_i8, rt_i16); // fail: runtime i16 -> i8

a10: std::array<i8, 2>;
a10 = (ce_i16, ce_i8);
a11: std::array<i8, 2>;
a11 = (ce_i16, ce_i16);
a12: std::array<i8, 2>;
a12 = (ce_i16, rt_i8);
a13: std::array<i8, 2>;
a13 = (ce_i16, rt_i16); // fail: runtime i16 -> i8

a20: std::array<i8, 2>;
a20 = (rt_i8, ce_i8);
a21: std::array<i8, 2>;
a21 = (rt_i8, ce_i16);
a22: std::array<i8, 2>;
a22 = (rt_i8, rt_i8);
a23: std::array<i8, 2>;
a23 = (rt_i8, rt_i16); // fail: runtime i16 -> i8

a30: std::array<i8, 2>;
a30 = (rt_i16, ce_i8); // fail: runtime i16 -> i8
a31: std::array<i8, 2>;
a31 = (rt_i16, ce_i16); // fail: runtime i16 -> i8
a32: std::array<i8, 2>;
a32 = (rt_i16, rt_i8); // fail: runtime i16 -> i8
a33: std::array<i8, 2>;
a33 = (rt_i16, rt_i16); // fail: runtime i16 -> i8
}

main: () -> int = {
rt_i8: i8 = 8;
rt_i16: i16 = 8;
try_all_combinations(rt_i8, rt_i16);
return 0;
}
15 changes: 15 additions & 0 deletions regression-tests/pure2-bugfix-for-deferred-init-narrowing-negative-literals.cpp2
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@@ -0,0 +1,15 @@
main: () -> int = {
a0: i8 = -1;
a: i8;
a = -1;

b0: i16 = -2;
b: i16;
b = -2;

c0: std::array<i8, 3> = (-3, -4, -5);
c: std::array<i8, 3>;
c = (-3, -4, -5);

return 0;
}
57 changes: 57 additions & 0 deletions ...t-results/clang-19-c++20/pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp.output
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@@ -0,0 +1,57 @@
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:19:125: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
19 | a03.construct_from([&]() -> typename CPP2_TYPEOF(a03)::value_type { return typename CPP2_TYPEOF(a03)::value_type{ce_i8, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:19:125: note: insert an explicit cast to silence this issue
19 | a03.construct_from([&]() -> typename CPP2_TYPEOF(a03)::value_type { return typename CPP2_TYPEOF(a03)::value_type{ce_i8, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:28:126: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
28 | a13.construct_from([&]() -> typename CPP2_TYPEOF(a13)::value_type { return typename CPP2_TYPEOF(a13)::value_type{ce_i16, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:28:126: note: insert an explicit cast to silence this issue
28 | a13.construct_from([&]() -> typename CPP2_TYPEOF(a13)::value_type { return typename CPP2_TYPEOF(a13)::value_type{ce_i16, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:37:125: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
37 | a23.construct_from([&]() -> typename CPP2_TYPEOF(a23)::value_type { return typename CPP2_TYPEOF(a23)::value_type{rt_i8, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:37:125: note: insert an explicit cast to silence this issue
37 | a23.construct_from([&]() -> typename CPP2_TYPEOF(a23)::value_type { return typename CPP2_TYPEOF(a23)::value_type{rt_i8, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:40:118: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
40 | a30.construct_from([&]() -> typename CPP2_TYPEOF(a30)::value_type { return typename CPP2_TYPEOF(a30)::value_type{rt_i16, ce_i8}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:40:118: note: insert an explicit cast to silence this issue
40 | a30.construct_from([&]() -> typename CPP2_TYPEOF(a30)::value_type { return typename CPP2_TYPEOF(a30)::value_type{rt_i16, ce_i8}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:42:118: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
42 | a31.construct_from([&]() -> typename CPP2_TYPEOF(a31)::value_type { return typename CPP2_TYPEOF(a31)::value_type{rt_i16, ce_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:42:118: note: insert an explicit cast to silence this issue
42 | a31.construct_from([&]() -> typename CPP2_TYPEOF(a31)::value_type { return typename CPP2_TYPEOF(a31)::value_type{rt_i16, ce_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:44:118: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
44 | a32.construct_from([&]() -> typename CPP2_TYPEOF(a32)::value_type { return typename CPP2_TYPEOF(a32)::value_type{rt_i16, rt_i8}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:44:118: note: insert an explicit cast to silence this issue
44 | a32.construct_from([&]() -> typename CPP2_TYPEOF(a32)::value_type { return typename CPP2_TYPEOF(a32)::value_type{rt_i16, rt_i8}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:46:118: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
46 | a33.construct_from([&]() -> typename CPP2_TYPEOF(a33)::value_type { return typename CPP2_TYPEOF(a33)::value_type{rt_i16, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:46:118: note: insert an explicit cast to silence this issue
46 | a33.construct_from([&]() -> typename CPP2_TYPEOF(a33)::value_type { return typename CPP2_TYPEOF(a33)::value_type{rt_i16, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:46:126: error: non-constant-expression cannot be narrowed from type 'cpp2::impl::in<cpp2::i16>' (aka 'const short') to 'signed char' in initializer list [-Wc++11-narrowing]
46 | a33.construct_from([&]() -> typename CPP2_TYPEOF(a33)::value_type { return typename CPP2_TYPEOF(a33)::value_type{rt_i16, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
pure2-bugfix-for-deferred-init-narrowing-matrix-error.cpp2:46:126: note: insert an explicit cast to silence this issue
46 | a33.construct_from([&]() -> typename CPP2_TYPEOF(a33)::value_type { return typename CPP2_TYPEOF(a33)::value_type{rt_i16, rt_i16}; });// fail: runtime i16 -> i8
| ^~~~~~
| static_cast<signed char>( )
8 errors generated.
4 changes: 2 additions & 2 deletions regression-tests/test-results/clang-19-c++23-libcpp/mixed-lifetime-safety-pointer-init-4.cpp
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Expand Up @@ -41,10 +41,10 @@ bool flip_a_coin() {

// ... more code ...
if (flip_a_coin()) {
p.construct(&y);
p.construct_from([&]() -> typename CPP2_TYPEOF(p)::value_type { return typename CPP2_TYPEOF(p)::value_type{&y}; });
}
else {
p.construct(&x);
p.construct_from([&]() -> typename CPP2_TYPEOF(p)::value_type { return typename CPP2_TYPEOF(p)::value_type{&x}; });
}

print_and_decorate(*cpp2::impl::assert_not_null(cpp2::move(p.value())));
Expand Down
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