From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 26 Aug 2020 13:47:51 +0000 (+0100)
Subject: libstdc++: Enable assertions in constexpr string_view members [PR 71960]
X-Git-Tag: releases/gcc-9.4.0~730
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=42fb390082b59c0b5af6a9f1e5a2e608ccb8e193;p=thirdparty%2Fgcc.git

libstdc++: Enable assertions in constexpr string_view members [PR 71960]

Since GCC 6.1 there is no reason we can't just use __glibcxx_assert in
constexpr functions in string_view. As long as the condition is true,
there will be no call to std::__replacement_assert that would make the
function ineligible for constant evaluation.

	PR libstdc++/71960
	* include/experimental/string_view (basic_string_view):
	Enable debug assertions.
	* include/std/string_view (basic_string_view):
	Likewise.

(cherry picked from commit 3eefb302d2bd8502cb3d8fe44e672b11092ccaf6)
---

diff --git a/libstdc++-v3/include/experimental/string_view b/libstdc++-v3/include/experimental/string_view
index 9e810dec8445..78c4d332b275 100644
--- a/libstdc++-v3/include/experimental/string_view
+++ b/libstdc++-v3/include/experimental/string_view
@@ -178,8 +178,7 @@ inline namespace fundamentals_v1
       constexpr const _CharT&
       operator[](size_type __pos) const
       {
-	// TODO: Assert to restore in a way compatible with the constexpr.
-	// __glibcxx_assert(__pos < this->_M_len);
+	__glibcxx_assert(__pos < this->_M_len);
 	return *(this->_M_str + __pos);
       }
 
@@ -198,16 +197,14 @@ inline namespace fundamentals_v1
       constexpr const _CharT&
       front() const
       {
-	// TODO: Assert to restore in a way compatible with the constexpr.
-	// __glibcxx_assert(this->_M_len > 0);
+	__glibcxx_assert(this->_M_len > 0);
 	return *this->_M_str;
       }
 
       constexpr const _CharT&
       back() const
       {
-	// TODO: Assert to restore in a way compatible with the constexpr.
-	// __glibcxx_assert(this->_M_len > 0);
+	__glibcxx_assert(this->_M_len > 0);
 	return *(this->_M_str + this->_M_len - 1);
       }
 
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index 4d90438e6be1..b7a0421950e3 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -193,8 +193,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr const_reference
       operator[](size_type __pos) const noexcept
       {
-	// TODO: Assert to restore in a way compatible with the constexpr.
-	// __glibcxx_assert(__pos < this->_M_len);
+	__glibcxx_assert(__pos < this->_M_len);
 	return *(this->_M_str + __pos);
       }
 
@@ -211,16 +210,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr const_reference
       front() const noexcept
       {
-	// TODO: Assert to restore in a way compatible with the constexpr.
-	// __glibcxx_assert(this->_M_len > 0);
+	__glibcxx_assert(this->_M_len > 0);
 	return *this->_M_str;
       }
 
       constexpr const_reference
       back() const noexcept
       {
-	// TODO: Assert to restore in a way compatible with the constexpr.
-	// __glibcxx_assert(this->_M_len > 0);
+	__glibcxx_assert(this->_M_len > 0);
 	return *(this->_M_str + this->_M_len - 1);
       }