[gcc r12-2543] libstdc++: Simplify std::optional::value()

Jonathan Wakely redi@gcc.gnu.org
Tue Jul 27 20:36:10 GMT 2021


https://gcc.gnu.org/g:9360d6cd1706882dfffd3c7a08b5956c37207a11

commit r12-2543-g9360d6cd1706882dfffd3c7a08b5956c37207a11
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jul 27 14:50:28 2021 +0100

    libstdc++: Simplify std::optional::value()
    
    The structure of these functions likely dates from the time before G++
    fully supported C++14 extended constexpr, so that the throw expression
    had to be the operand of a conditional expression. That is not true now,
    so we can use a more straightforward version of the code.
    
    We can also simplify the declaration of __throw_bad_optional_access by
    using the C++11-style [[noreturn]] attribute so that a separate
    declaration isn't needed.
    
    libstdc++-v3/ChangeLog:
    
            * include/experimental/optional (__throw_bad_optional_access):
            Replace GNU attribute with C++11 attribute.
            (optional::value, optional::value_or): Use if statements
            instead of conditional expressions.
            * include/std/optional (__throw_bad_optional_access)
            (optional::value, optional::value_or): Likewise.

Diff:
---
 libstdc++-v3/include/experimental/optional | 56 +++++++++++++-----------------
 libstdc++-v3/include/std/optional          | 43 +++++++++++------------
 2 files changed, 46 insertions(+), 53 deletions(-)

diff --git a/libstdc++-v3/include/experimental/optional b/libstdc++-v3/include/experimental/optional
index 431d23631cf..274c974853d 100644
--- a/libstdc++-v3/include/experimental/optional
+++ b/libstdc++-v3/include/experimental/optional
@@ -114,12 +114,8 @@ inline namespace fundamentals_v1
 
   /// @cond undocumented
 
-  void
-  __throw_bad_optional_access(const char*)
-  __attribute__((__noreturn__));
-
   // XXX Does not belong here.
-  inline void
+  [[noreturn]] inline void
   __throw_bad_optional_access(const char* __s)
   { _GLIBCXX_THROW_OR_ABORT(bad_optional_access(__s)); }
 
@@ -674,41 +670,37 @@ inline namespace fundamentals_v1
       constexpr const _Tp&
       value() const&
       {
-	return this->_M_is_engaged()
-	  ?  this->_M_get()
-	  : (__throw_bad_optional_access("Attempt to access value of a "
-		                         "disengaged optional object"),
-	     this->_M_get());
+	if (this->_M_is_engaged())
+	  return this->_M_get();
+	__throw_bad_optional_access("Attempt to access value of a "
+				    "disengaged optional object");
       }
 
       constexpr _Tp&
       value()&
       {
-	return this->_M_is_engaged()
-	  ?  this->_M_get()
-	  : (__throw_bad_optional_access("Attempt to access value of a "
-		                         "disengaged optional object"),
-	     this->_M_get());
+	if (this->_M_is_engaged())
+	  return this->_M_get();
+	__throw_bad_optional_access("Attempt to access value of a "
+				    "disengaged optional object");
       }
 
       constexpr _Tp&&
       value()&&
       {
-	return this->_M_is_engaged()
-	  ?  std::move(this->_M_get())
-	  : (__throw_bad_optional_access("Attempt to access value of a "
-		                         "disengaged optional object"),
-	     std::move(this->_M_get()));
+	if (this->_M_is_engaged())
+	  return std::move(this->_M_get());
+	__throw_bad_optional_access("Attempt to access value of a "
+				    "disengaged optional object");
       }
 
       constexpr const _Tp&&
       value() const&&
       {
-	return this->_M_is_engaged()
-	  ?  std::move(this->_M_get())
-	  : (__throw_bad_optional_access("Attempt to access value of a "
-		                         "disengaged optional object"),
-	     std::move(this->_M_get()));
+	if (this->_M_is_engaged())
+	  return std::move(this->_M_get());
+	__throw_bad_optional_access("Attempt to access value of a "
+				    "disengaged optional object");
       }
 
       template<typename _Up>
@@ -719,9 +711,10 @@ inline namespace fundamentals_v1
 			       is_convertible<_Up&&, _Tp>>(),
 			"Cannot return value");
 
-	  return this->_M_is_engaged()
-	    ? this->_M_get()
-	    : static_cast<_Tp>(std::forward<_Up>(__u));
+	  if (this->_M_is_engaged())
+	    return this->_M_get();
+	  else
+	    return static_cast<_Tp>(std::forward<_Up>(__u));
 	}
 
       template<typename _Up>
@@ -732,9 +725,10 @@ inline namespace fundamentals_v1
 			       is_convertible<_Up&&, _Tp>>(),
 			"Cannot return value" );
 
-	  return this->_M_is_engaged()
-	    ? std::move(this->_M_get())
-	    : static_cast<_Tp>(std::forward<_Up>(__u));
+	  if (this->_M_is_engaged())
+	    return std::move(this->_M_get());
+	  else
+	    return static_cast<_Tp>(std::forward<_Up>(__u));
 	}
     };
 
diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional
index df9ed0736b3..b8ab7510757 100644
--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -91,12 +91,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return "bad optional access"; }
   };
 
-  void
-  __throw_bad_optional_access()
-  __attribute__((__noreturn__));
-
   // XXX Does not belong here.
-  inline void
+  [[__noreturn__]] inline void
   __throw_bad_optional_access()
   { _GLIBCXX_THROW_OR_ABORT(bad_optional_access()); }
 
@@ -943,33 +939,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr const _Tp&
       value() const&
       {
-	return this->_M_is_engaged()
-	  ? this->_M_get()
-	  : (__throw_bad_optional_access(), this->_M_get());
+	if (this->_M_is_engaged())
+	  return this->_M_get();
+	__throw_bad_optional_access();
       }
 
       constexpr _Tp&
       value()&
       {
-	return this->_M_is_engaged()
-	  ? this->_M_get()
-	  : (__throw_bad_optional_access(), this->_M_get());
+	if (this->_M_is_engaged())
+	  return this->_M_get();
+	__throw_bad_optional_access();
       }
 
       constexpr _Tp&&
       value()&&
       {
-	return this->_M_is_engaged()
-	  ? std::move(this->_M_get())
-	  : (__throw_bad_optional_access(), std::move(this->_M_get()));
+	if (this->_M_is_engaged())
+	  return std::move(this->_M_get());
+	__throw_bad_optional_access();
       }
 
       constexpr const _Tp&&
       value() const&&
       {
-	return this->_M_is_engaged()
-	  ? std::move(this->_M_get())
-	  : (__throw_bad_optional_access(), std::move(this->_M_get()));
+	if (this->_M_is_engaged())
+	  return std::move(this->_M_get());
+	__throw_bad_optional_access();
       }
 
       template<typename _Up>
@@ -979,8 +975,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  static_assert(is_copy_constructible_v<_Tp>);
 	  static_assert(is_convertible_v<_Up&&, _Tp>);
 
-	  return this->_M_is_engaged()
-	    ? this->_M_get() : static_cast<_Tp>(std::forward<_Up>(__u));
+	  if (this->_M_is_engaged())
+	    return this->_M_get();
+	  else
+	    return static_cast<_Tp>(std::forward<_Up>(__u));
 	}
 
       template<typename _Up>
@@ -990,9 +988,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  static_assert(is_move_constructible_v<_Tp>);
 	  static_assert(is_convertible_v<_Up&&, _Tp>);
 
-	  return this->_M_is_engaged()
-	    ? std::move(this->_M_get())
-	    : static_cast<_Tp>(std::forward<_Up>(__u));
+	  if (this->_M_is_engaged())
+	    return std::move(this->_M_get());
+	  else
+	    return static_cast<_Tp>(std::forward<_Up>(__u));
 	}
 
       void reset() noexcept { this->_M_reset(); }


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