Rewrite gdb_mpz::operator==

Simon pointed out that the recent changes to gdb_mpz caused a build
failure on amd64 macOS.  It turns out to be somewhat difficult to
overload a method in a way that will work "naturally" for all integer
types; especially in a case like gdb_mpz::operator==, where it's
desirable to special case all integer types that are no wider than
'long'.

After a false start, I came up with this patch, which seems to work.
It applies the desirable GMP special cases directly in the body,
rather than via overloads.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

diff --git a/gdb/gmp-utils.h b/gdb/gmp-utils.h
index d05c11ecbe4ba3304e5f5b88e40e8d3d9063c0c1..a5c27feb59ff87006bc272d299048df1a13a67dc 100644 (file)
--- a/gdb/gmp-utils.h
+++ b/gdb/gmp-utils.h
@@ -323,31 +323,25 @@ struct gdb_mpz
     return mpz_cmp_si (m_val, other) < 0;
   }
 
-  bool operator== (int other) const
-  {
-    return mpz_cmp_si (m_val, other) == 0;
-  }
-
-  bool operator== (long other) const
-  {
-    return mpz_cmp_si (m_val, other) == 0;
-  }
-
-  bool operator== (unsigned long other) const
-  {
-    return mpz_cmp_ui (m_val, other) == 0;
-  }
-
-  template<typename T,
-          typename = gdb::Requires<
-            gdb::And<std::is_integral<T>,
-                     std::integral_constant<bool,
-                                            (sizeof (T) > sizeof (long))>>
-            >
-          >
-  bool operator== (T src)
-  {
-    return *this == gdb_mpz (src);
+  /* We want an operator== that can handle all integer types.  For
+     types that are 'long' or narrower, we can use a GMP function and
+     avoid boxing the RHS.  But, because overloading based on integer
+     type is a pain in C++, we accept all such types here and check
+     the size in the body.  */
+  template<typename T, typename = gdb::Requires<std::is_integral<T>>>
+  bool operator== (T other) const
+  {
+    if (std::is_signed<T>::value)
+      {
+       if (sizeof (T) <= sizeof (long))
+         return mpz_cmp_si (m_val, other) == 0;
+      }
+    else
+      {
+       if (sizeof (T) <= sizeof (unsigned long))
+         return mpz_cmp_ui (m_val, other) == 0;
+      }
+    return *this == gdb_mpz (other);
   }
 
   bool operator== (const gdb_mpz &other) const