[committed] libstdc++: Fix warnings with -Wsystem-headers

[Jonathan Wakely via Gcc-patches]

libstdc++-v3/ChangeLog:

        * include/bits/stl_algobase.h (__find_if): Add FALLTHRU markers.
        * include/std/charconv (__detail::__to_chars): Avoid
        -Wsign-compare warning.

Tested powerpc64le-linux, committed to master.



commit 25920dd18ad12ea501309b1487366e22f35db631
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Wed Jun 24 12:34:17 2020 +0100

    libstdc++: Fix warnings with -Wsystem-headers
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/stl_algobase.h (__find_if): Add FALLTHRU markers.
            * include/std/charconv (__detail::__to_chars): Avoid
            -Wsign-compare warning.

diff --git a/libstdc++-v3/include/bits/stl_algobase.h 
b/libstdc++-v3/include/bits/stl_algobase.h
index 4fc8850d707..ff5b4505a08 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -2092,14 +2092,17 @@ _GLIBCXX_END_NAMESPACE_ALGO
          if (__pred(__first))
            return __first;
          ++__first;
+         // FALLTHRU
        case 2:
          if (__pred(__first))
            return __first;
          ++__first;
+         // FALLTHRU
        case 1:
          if (__pred(__first))
            return __first;
          ++__first;
+         // FALLTHRU
        case 0:
        default:
          return __last;
diff --git a/libstdc++-v3/include/std/charconv 
b/libstdc++-v3/include/std/charconv
index 77a72d40dd0..8fbf64058ee 100644
--- a/libstdc++-v3/include/std/charconv
+++ b/libstdc++-v3/include/std/charconv
@@ -142,7 +142,7 @@ namespace __detail
        'u', 'v', 'w', 'x', 'y', 'z'
       };
 
-      while (__val >= __base)
+      while (__val >= (unsigned)__base)
        {
          auto const __quo = __val / __base;
          auto const __rem = __val % __base;