ilya-biryukov created this revision.
ilya-biryukov added a reviewer: jyknight.
Herald added a project: All.
ilya-biryukov requested review of this revision.
Herald added a project: clang.
They must be evaluated in the context where default argument is actually
used during a call, not in a parameter list where default argument is specified.
This affects correctness of `std::source_location`.
Fixes #56379.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D129488
Files:
clang/include/clang/Sema/Sema.h
clang/lib/Sema/SemaExpr.cpp
clang/test/SemaCXX/source_location.cpp
clang/test/SemaCXX/source_location_consteval.cpp
Index: clang/test/SemaCXX/source_location_consteval.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/source_location_consteval.cpp
@@ -0,0 +1,59 @@
+// RUN: %clang_cc1 -std=c++20 -verify %s
+// expected-no-diagnostics
+
+namespace std {
+class source_location {
+ struct __impl;
+
+public:
+ static consteval source_location current(const __impl *__p = __builtin_source_location()) noexcept {
+ source_location __loc;
+ __loc.__m_impl = __p;
+ return __loc;
+ }
+ constexpr source_location() = default;
+ constexpr source_location(source_location const &) = default;
+ constexpr unsigned int line() const noexcept { return __m_impl ? __m_impl->_M_line : 0; }
+ constexpr unsigned int column() const noexcept { return __m_impl ? __m_impl->_M_column : 0; }
+ constexpr const char *file() const noexcept { return __m_impl ? __m_impl->_M_file_name : ""; }
+ constexpr const char *function() const noexcept { return __m_impl ? __m_impl->_M_function_name : ""; }
+
+private:
+ // Note: The type name "std::source_location::__impl", and its constituent
+ // field-names are required by __builtin_source_location().
+ struct __impl {
+ const char *_M_file_name;
+ const char *_M_function_name;
+ unsigned _M_line;
+ unsigned _M_column;
+ };
+ const __impl *__m_impl = nullptr;
+
+public:
+ using public_impl_alias = __impl;
+};
+} // namespace std
+
+using SL = std::source_location;
+
+constexpr bool is_equal(const char *LHS, const char *RHS) {
+ while (*LHS != 0 && *RHS != 0) {
+ if (*LHS != *RHS)
+ return false;
+ ++LHS;
+ ++RHS;
+ }
+ return *LHS == 0 && *RHS == 0;
+}
+
+constexpr SL get_sl(SL l = SL::current()) { return l; }
+
+#line 700 "CheckDefaultArg.h"
+constexpr SL l = get_sl();
+static_assert(l.line() == 700);
+static_assert(is_equal(l.file(), "CheckDefaultArg.h"));
+
+void test() {
+ static_assert(is_equal(get_sl().function(), __PRETTY_FUNCTION__));
+ static_assert(get_sl().line() == __LINE__);
+}
Index: clang/test/SemaCXX/source_location.cpp
===================================================================
--- clang/test/SemaCXX/source_location.cpp
+++ clang/test/SemaCXX/source_location.cpp
@@ -364,8 +364,8 @@
template <class T>
void func_template_tests() {
constexpr auto P = test_func_template(42);
- //static_assert(is_equal(P.first.function(), __func__), "");
- //static_assert(!is_equal(P.second.function(), __func__), "");
+ static_assert(is_equal(P.first.function(), __PRETTY_FUNCTION__), "");
+ static_assert(!is_equal(P.second.function(), __PRETTY_FUNCTION__), "");
}
template void func_template_tests<int>();
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -17500,7 +17500,8 @@
/*IsImmediateInvocation*/ true);
/// Value-dependent constant expressions should not be immediately
/// evaluated until they are instantiated.
- if (!Res->isValueDependent())
+ /// Default arguments must be evaluated in the context of their call.
+ if (!Res->isValueDependent() && !isPotentiallyEvaluatedIfUsedContext())
ExprEvalContexts.back().ImmediateInvocationCandidates.emplace_back(Res, 0);
return Res;
}
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -1359,6 +1359,10 @@
ExpressionEvaluationContext::ImmediateFunctionContext &&
InDiscardedStatement);
}
+
+ bool isPotentiallyEvaluatedIfUsed() const {
+ return Context == ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed;
+ }
};
/// A stack of expression evaluation contexts.
@@ -9406,6 +9410,12 @@
return ExprEvalContexts.back().isImmediateFunctionContext();
}
+ bool isPotentiallyEvaluatedIfUsedContext() const {
+ assert(!ExprEvalContexts.empty() &&
+ "Must be in an expression evaluation context");
+ return ExprEvalContexts.back().isPotentiallyEvaluatedIfUsed();
+ }
+
/// RAII class used to determine whether SFINAE has
/// trapped any errors that occur during template argument
/// deduction.
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