[gcc r13-787] libstdc++: Fix narrowing conversions for 16-bit size_t [PR105681]

[Jonathan Wakely]

https://gcc.gnu.org/g:367740bf6d3a6627798b3955e5d85efc7549ef50

commit r13-787-g367740bf6d3a6627798b3955e5d85efc7549ef50
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu May 26 21:32:55 2022 +0100

    libstdc++: Fix narrowing conversions for 16-bit size_t [PR105681]
    
    On a 16-bit target such as msp430 we get errors about narrowing long
    values to size_t, which is only 16-bit. When --enable-libstdcxx-pch is
    used the <bits/extc++.h> header breaks the build because of these
    narrowing errors.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/105681
            * include/ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp:
            Limit ga_sizes array to values that fit in size_t.
            * include/ext/random [__SIZE_WIDTH < 32] (sfmt86243)
            (sfmt86243_64, sfmt132049, sfmt132049_64, sfmt216091)
            (sfmt216091_64): Do not declare.

Diff:
---
 .../resize_policy/hash_prime_size_policy_imp.hpp       | 18 +++++++++++++++---
 libstdc++-v3/include/ext/random                        |  2 ++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp b/libstdc++-v3/include/ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp
index d53392c8211..43d72768206 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp
@@ -46,15 +46,23 @@ namespace detail
 {
   enum
     {
+      num_distinct_sizes_16_bit = 14,
       num_distinct_sizes_32_bit = 30,
       num_distinct_sizes_64_bit = 62,
-      num_distinct_sizes = sizeof(std::size_t) != 8 ? 
-            num_distinct_sizes_32_bit : num_distinct_sizes_64_bit,	
+      // The number of values is limited by the width of size_t.
+      // Maybe we could just use (__SIZE_WIDTH__ - 2) here.
+#if __SIZE_WIDTH__ >= 64
+      num_distinct_sizes =  num_distinct_sizes_64_bit
+#elif __SIZE_WIDTH__ >= 32
+      num_distinct_sizes =  num_distinct_sizes_32_bit
+#else
+      num_distinct_sizes =  num_distinct_sizes_16_bit
+#endif
     };
 
   // Originally taken from the SGI implementation; acknowledged in the docs.
   // Further modified (for 64 bits) from tr1's hashtable.
-  static const std::size_t g_a_sizes[num_distinct_sizes_64_bit] =
+  static const std::size_t g_a_sizes[num_distinct_sizes] =
     {
       /* 0     */              5ul,
       /* 1     */              11ul, 
@@ -70,6 +78,7 @@ namespace detail
       /* 11    */              14033ul, 
       /* 12    */              28411ul, 
       /* 13    */              57557ul, 
+#if __SIZE_WIDTH__ >= 32
       /* 14    */              116731ul, 
       /* 15    */              236897ul,
       /* 16    */              480881ul, 
@@ -86,6 +95,7 @@ namespace detail
       /* 27    */              1164186217ul,
       /* 28    */              2364114217ul, 
       /* 29    */              4294967291ul,
+#if __SIZE_WIDTH__ >= 64
       /* 30    */ (std::size_t)8589934583ull,
       /* 31    */ (std::size_t)17179869143ull,
       /* 32    */ (std::size_t)34359738337ull,
@@ -118,6 +128,8 @@ namespace detail
       /* 59    */ (std::size_t)4611686018427387847ull,
       /* 60    */ (std::size_t)9223372036854775783ull,
       /* 61    */ (std::size_t)18446744073709551557ull,
+#endif
+#endif
     };
 
 } // namespace detail
diff --git a/libstdc++-v3/include/ext/random b/libstdc++-v3/include/ext/random
index b7155767b02..50505b876cc 100644
--- a/libstdc++-v3/include/ext/random
+++ b/libstdc++-v3/include/ext/random
@@ -346,6 +346,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 					    0xa3ac4000U, 0xecc1327aU>
     sfmt44497_64;
 
+#if __SIZE_WIDTH__ >= 32
 
   typedef simd_fast_mersenne_twister_engine<uint32_t, 86243, 366,
 					    6, 7, 19, 1,
@@ -396,6 +397,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 					    0xf8000001U, 0x89e80709U,
 					    0x3bd2b64bU, 0x0c64b1e4U>
     sfmt216091_64;
+#endif // __SIZE_WIDTH__ >= 32
 
 #endif // __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__