[gcc r12-8213] libstdc++: Remove bogus assertion in std::from_chars [PR105324]

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

https://gcc.gnu.org/g:cf37107522f465d9e12af01ba68d2d1df0f18d46

commit r12-8213-gcf37107522f465d9e12af01ba68d2d1df0f18d46
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Apr 21 11:26:49 2022 +0100

    libstdc++: Remove bogus assertion in std::from_chars [PR105324]
    
    I'm not sure what I was thinking when I added this assertion, maybe it
    was supposed to be alignment == 1 (which is what the pmr::string actually
    uses). The simplest fix is to just remove the assertion.
    
    The assertion is no longer enabled by default on trunk, but it's still
    there for the --enablke-libstdcxx-debug build, and is still wrong. The
    fix is needed on the gcc-11 branch.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/105324
            * src/c++17/floating_from_chars.cc (buffer_resource::do_allocate):
            Remove assertion.
            * testsuite/20_util/from_chars/pr105324.cc: New test.

Diff:
---
 libstdc++-v3/src/c++17/floating_from_chars.cc         |  1 -
 libstdc++-v3/testsuite/20_util/from_chars/pr105324.cc | 14 ++++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/src/c++17/floating_from_chars.cc b/libstdc++-v3/src/c++17/floating_from_chars.cc
index bbe03f7f068..0f5183aa9b5 100644
--- a/libstdc++-v3/src/c++17/floating_from_chars.cc
+++ b/libstdc++-v3/src/c++17/floating_from_chars.cc
@@ -101,7 +101,6 @@ namespace
 	return m_buf + std::__exchange(m_bytes, m_bytes + bytes);
 
       __glibcxx_assert(m_ptr == nullptr);
-      __glibcxx_assert(alignment != 1);
 
       m_ptr = operator new(bytes);
       m_bytes = bytes;
diff --git a/libstdc++-v3/testsuite/20_util/from_chars/pr105324.cc b/libstdc++-v3/testsuite/20_util/from_chars/pr105324.cc
new file mode 100644
index 00000000000..cecb17e41cc
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/from_chars/pr105324.cc
@@ -0,0 +1,14 @@
+// { dg-do run { target c++17 } }
+
+#include <charconv>
+#include <string>
+
+int main()
+{
+  // PR libstdc++/105324
+  // std::from_chars() assertion at floating_from_chars.cc:78
+  std::string s(512, '1');
+  s[1] = '.';
+  long double d;
+  std::from_chars(s.data(), s.data() + s.size(), d);
+}