Re: [PATCH] Rewrite gdb_mpz::operator==

[Tom Tromey <tromey@adacore.com>]

Tom> I feel like it happened in the past, but maybe it doesn't any more.
Tom> I'll rewrite this patch.

Here's v3.

Tom

commit f12c9b23d3ac219e08818935930f5ee891396158
Author: Tom Tromey <tromey@adacore.com>
Date:   Mon Apr 17 12:59:57 2023 -0600

    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.

diff --git a/gdb/gmp-utils.h b/gdb/gmp-utils.h
index d05c11ecbe4..1bbdd9564fa 100644
--- a/gdb/gmp-utils.h
+++ b/gdb/gmp-utils.h
@@ -323,31 +323,26 @@ 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;
-  }
-
+  /* 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<
-	     gdb::And<std::is_integral<T>,
-		      std::integral_constant<bool,
-					     (sizeof (T) > sizeof (long))>>
-	     >
-	   >
-  bool operator== (T src)
-  {
-    return *this == gdb_mpz (src);
+	   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