[gcc r11-11127] libstdc++: Add assertion to std::string_view::remove_suffix [PR112314]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:4f74f6c7aa0820943ba0777dc41d69a969576e18

commit r11-11127-g4f74f6c7aa0820943ba0777dc41d69a969576e18
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Nov 1 15:01:22 2023 +0000

    libstdc++: Add assertion to std::string_view::remove_suffix [PR112314]
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/112314
            * include/std/string_view (string_view::remove_suffix): Add
            debug assertion.
            * testsuite/21_strings/basic_string_view/modifiers/remove_prefix/debug.cc:
            New test.
            * testsuite/21_strings/basic_string_view/modifiers/remove_suffix/debug.cc:
            New test.
    
    (cherry picked from commit 6afa984f47e16e8bd958646d7407b74e61041f5d)

Diff:
---
 libstdc++-v3/include/std/string_view                       |  5 ++++-
 .../basic_string_view/modifiers/remove_prefix/debug.cc     | 14 ++++++++++++++
 .../basic_string_view/modifiers/remove_suffix/debug.cc     | 14 ++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index 68df70e99f1..8e3db15ca03 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -275,7 +275,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       constexpr void
       remove_suffix(size_type __n) noexcept
-      { this->_M_len -= __n; }
+      {
+	__glibcxx_assert(this->_M_len >= __n);
+	this->_M_len -= __n;
+      }
 
       constexpr void
       swap(basic_string_view& __sv) noexcept
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/modifiers/remove_prefix/debug.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/modifiers/remove_prefix/debug.cc
new file mode 100644
index 00000000000..37204583b71
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/modifiers/remove_prefix/debug.cc
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++17 } }
+
+#include <string_view>
+
+constexpr bool
+check_remove_prefix()
+{
+  std::string_view sv("123");
+  sv.remove_prefix(4);
+  // { dg-error "not a constant expression" "" { target *-*-* } 0 }
+  return true;
+}
+
+constexpr bool test = check_remove_prefix();
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/modifiers/remove_suffix/debug.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/modifiers/remove_suffix/debug.cc
new file mode 100644
index 00000000000..a549e4c2471
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/modifiers/remove_suffix/debug.cc
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++17 } }
+
+#include <string_view>
+
+constexpr bool
+check_remove_suffix()
+{
+  std::string_view sv("123");
+  sv.remove_suffix(4);
+  // { dg-error "not a constant expression" "" { target *-*-* } 0 }
+  return true;
+}
+
+constexpr bool test = check_remove_suffix();