[clang] ICE when dealing with some certain requires clauses in calculateConstraintSatisfaction
#69307
Labels
c++20
clang:frontend
Language frontend issues, e.g. anything involving "Sema"
concepts
C++20 concepts
crash
Prefer [crash-on-valid] or [crash-on-invalid]
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@llvm/issue-subscribers-clang-frontend Author: Runge (RungeCC)
## Descriptions
#include <concepts>
#include <type_traits>
#include <utility>
[[maybe_unused]] constexpr inline static auto lpartial =
[](auto fn, auto... t0) constexpr noexcept {
return [=](auto... rest) constexpr noexcept
requires requires { fn(t0..., rest...); }
{ return fn(t0..., rest...); };
};
[[maybe_unused]] constexpr inline static auto fix =
[](auto self) constexpr noexcept {
return [=](auto... args) constexpr noexcept
requires requires { self(self, args...); }
{ return self(self, args...); };
};
[[maybe_unused]] constexpr inline static auto currify0 =
[](auto self, auto v, auto fn) constexpr noexcept {
return [=](auto... as) constexpr noexcept
requires(
(v.value > sizeof...(as) && requires { lpartial(fn, as...); }) ||
(v.value == sizeof...(as) && requires { fn(as...); }))
{
if constexpr (v.value > sizeof...(as))
return self(self, std::integral_constant<std::size_t, v.value - sizeof...(as)>{}, lpartial(fn, as...));
else
return fn(as...);
};
};
[[maybe_unused]] constexpr static inline auto plus =
[](auto x, auto y) constexpr noexcept
requires requires { x + y; }
{ return x + y; };
#undef lambda_body
[[maybe_unused]] constexpr static inline auto plus_ =
fix(currify0)(std::integral_constant<std::size_t, 2>{}, plus);
Expected behavior: Accepts the above code, just as Actual behavior: Crash, with output: <details> </details> Versions: trunk(Online compiler, with assertions) and: Notes
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@llvm/issue-subscribers-c-20 Author: Runge (RungeCC)
## Descriptions
#include <concepts>
#include <type_traits>
#include <utility>
[[maybe_unused]] constexpr inline static auto lpartial =
[](auto fn, auto... t0) constexpr noexcept {
return [=](auto... rest) constexpr noexcept
requires requires { fn(t0..., rest...); }
{ return fn(t0..., rest...); };
};
[[maybe_unused]] constexpr inline static auto fix =
[](auto self) constexpr noexcept {
return [=](auto... args) constexpr noexcept
requires requires { self(self, args...); }
{ return self(self, args...); };
};
[[maybe_unused]] constexpr inline static auto currify0 =
[](auto self, auto v, auto fn) constexpr noexcept {
return [=](auto... as) constexpr noexcept
requires(
(v.value > sizeof...(as) && requires { lpartial(fn, as...); }) ||
(v.value == sizeof...(as) && requires { fn(as...); }))
{
if constexpr (v.value > sizeof...(as))
return self(self, std::integral_constant<std::size_t, v.value - sizeof...(as)>{}, lpartial(fn, as...));
else
return fn(as...);
};
};
[[maybe_unused]] constexpr static inline auto plus =
[](auto x, auto y) constexpr noexcept
requires requires { x + y; }
{ return x + y; };
#undef lambda_body
[[maybe_unused]] constexpr static inline auto plus_ =
fix(currify0)(std::integral_constant<std::size_t, 2>{}, plus);
Expected behavior: Accepts the above code, just as Actual behavior: Crash, with output: <details> </details> Versions: trunk(Online compiler, with assertions) and: Notes
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I have found a strange workaround: Convert a function call that will trigger clang ICE, like: into an equivalent form: Then clang could work with it, without crashing or emitting any warnings. See online compiler. |
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Possibly related: #67260 |
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A minimal example is: constexpr auto ICE = [](auto a) { // a dependent ParmVar
return [=]() // #1, ICE
// [&]() // #2, ICE
// [ ]() // #3, OK
// [r=a]() // #4, OK
// [a]() // #5, OK
// [&r=a]()// #6, OK with warning
// [&a]() // #7, OK with warning
requires requires { a; }
{ return 1; };
};
constexpr auto Ret = ICE(1)();constexpr auto ICE = [](auto a) {
return [=]()
requires requires { a; }
{ return a; }; // #8, implicitly captured, OK
};
constexpr auto Ret = ICE(1)();Note:
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I think the following code is suspicious: llvm-project/clang/lib/Sema/SemaExpr.cpp Lines 19787 to 19792 in 4f131b0 Consider: constexpr auto ICE(auto a) { // template function, not lambda
return [=]()
requires requires { a; }
{ return 1; };
};ICE happens when checking satisfaction of constraints of the It seems that before 3ed9e9e the above example is somehow like (ignoring incorrect syntax): constexpr auto ICE(auto a) { // template function, not lambda
return [=]()
{ requires requires { a; }; return 1; };
};llvm-project/clang/lib/Sema/SemaExpr.cpp Lines 19779 to 19815 in 4f131b0 As at that time llvm-project/clang/lib/Sema/SemaDecl.cpp Lines 15383 to 15386 in eaf725b CC: @cor3ntin Note: The above analysis may be completely wrong, as I've only recently started reading the clang source code. |
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I think this theory makes some sense, since I notice this: also triggers the same ICE(https://godbolt.org/z/cjc4arcTW). |
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I will submit a pull request to attempt to fix this issue. |
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Descriptions
Example:
Expected behavior:
Accepts the above code, just as
gcc(13.2 and trunk),msvc(latest) do.Actual behavior:
Crash, with output:
Click me
Versions:
trunk(Online compiler, with assertions) and:
Notes
requires requires ...in the decl of lambdafix, then clang-trunk will accept it.The text was updated successfully, but these errors were encountered: