[gcc r15-3255] libstdc++: avoid -Wsign-compare

[Jason Merrill]

https://gcc.gnu.org/g:4246cf4f18053eeb47cb2a241fffa9a41573916e

commit r15-3255-g4246cf4f18053eeb47cb2a241fffa9a41573916e
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Aug 27 13:17:20 2024 -0400

    libstdc++: avoid -Wsign-compare
    
    -Wsign-compare complained about these comparisons between (unsigned) size_t
    and (signed) streamsize, or between (unsigned) native_handle_type
    and (signed) -1.  Fixed by adding casts to unify the types.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/istream: Add cast to avoid -Wsign-compare.
            * include/std/stacktrace: Likewise.

Diff:
---
 libstdc++-v3/include/std/istream    | 2 +-
 libstdc++-v3/include/std/stacktrace | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/std/istream b/libstdc++-v3/include/std/istream
index a2b207dae78c..730e413c290b 100644
--- a/libstdc++-v3/include/std/istream
+++ b/libstdc++-v3/include/std/istream
@@ -909,7 +909,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  __n /= sizeof(_CharT);
 	  streamsize __w = __in.width();
 	  std::__istream_extract(__in, __s, __n);
-	  if (__in.good() && (__w <= 0 || __n < __w))
+	  if (__in.good() && (__w <= 0 || __n < (size_t)__w))
 	    {
 	      // Stopped extracting early to avoid overflowing the buffer,
 	      // but might have stopped anyway (and set eofbit) if at EOF.
diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
index e0a543920bc3..cd2606257fec 100644
--- a/libstdc++-v3/include/std/stacktrace
+++ b/libstdc++-v3/include/std/stacktrace
@@ -80,7 +80,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     constexpr native_handle_type
     native_handle() const noexcept { return _M_pc; }
 
-    constexpr explicit operator bool() const noexcept { return _M_pc != -1; }
+    constexpr explicit operator bool() const noexcept
+    { return _M_pc != (native_handle_type)-1; }
 
     // [stacktrace.entry.query], query
     [[nodiscard]]