[PATCH 1/7] [gdb/build, c++20] Fix Wdeprecated-enum-enum-conversion

[Tom de Vries <tdevries@suse.de>]

When building gdb with clang 15 and -std=c++20, I run into:
...
gdbsupport/common-exceptions.h:203:32: error: arithmetic between different \
  enumeration types ('const enum return_reason' and 'const enum errors') is \
  deprecated [-Werror,-Wdeprecated-enum-enum-conversion]
    size_t result = exc.reason + exc.error;
                    ~~~~~~~~~~ ^ ~~~~~~~~~
...

Fix this by using to_underlying.

Likewise in a few other places.

Tested on x86_64-linux.
---
 gdb/remote.c                   | 12 ++++++++----
 gdb/rs6000-tdep.c              |  3 ++-
 gdbsupport/common-exceptions.h |  4 +++-
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index 6fefabac0ce..e01da795ec8 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -10850,7 +10850,8 @@ remote_target::insert_watchpoint (CORE_ADDR addr, int len,
   char *p;
   enum Z_packet_type packet = watchpoint_to_Z_packet (type);
 
-  if (m_features.packet_support (PACKET_Z0 + packet) == PACKET_DISABLE)
+  if (m_features.packet_support ((to_underlying (PACKET_Z0)
+				  + to_underlying (packet))) == PACKET_DISABLE)
     return 1;
 
   /* Make sure the remote is pointing at the right process, if
@@ -10867,7 +10868,8 @@ remote_target::insert_watchpoint (CORE_ADDR addr, int len,
   putpkt (rs->buf);
   getpkt (&rs->buf, 0);
 
-  switch (m_features.packet_ok (rs->buf, PACKET_Z0 + packet))
+  switch (m_features.packet_ok (rs->buf, (to_underlying (PACKET_Z0)
+					  + to_underlying (packet))))
     {
     case PACKET_ERROR:
       return -1;
@@ -10898,7 +10900,8 @@ remote_target::remove_watchpoint (CORE_ADDR addr, int len,
   char *p;
   enum Z_packet_type packet = watchpoint_to_Z_packet (type);
 
-  if (m_features.packet_support (PACKET_Z0 + packet) == PACKET_DISABLE)
+  if (m_features.packet_support ((to_underlying (PACKET_Z0)
+				  + to_underlying (packet))) == PACKET_DISABLE)
     return -1;
 
   /* Make sure the remote is pointing at the right process, if
@@ -10914,7 +10917,8 @@ remote_target::remove_watchpoint (CORE_ADDR addr, int len,
   putpkt (rs->buf);
   getpkt (&rs->buf, 0);
 
-  switch (m_features.packet_ok (rs->buf, PACKET_Z0 + packet))
+  switch (m_features.packet_ok (rs->buf, (to_underlying (PACKET_Z0)
+					  + to_underlying (packet))))
     {
     case PACKET_ERROR:
     case PACKET_UNKNOWN:
diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
index ff83743da36..71390513ad2 100644
--- a/gdb/rs6000-tdep.c
+++ b/gdb/rs6000-tdep.c
@@ -2495,7 +2495,8 @@ rs6000_register_name (struct gdbarch *gdbarch, int regno)
 
   /* Hide the upper halves of the cvs0~cvs31 registers.  */
   if (PPC_CVSR0_UPPER_REGNUM <= regno
-      && regno < PPC_CVSR0_UPPER_REGNUM + ppc_num_gprs)
+      && regno < (to_underlying (PPC_CVSR0_UPPER_REGNUM)
+		  + to_underlying (ppc_num_gprs)))
     return "";
 
   /* Check if the SPE pseudo registers are available.  */
diff --git a/gdbsupport/common-exceptions.h b/gdbsupport/common-exceptions.h
index f9b59ece736..e4750211448 100644
--- a/gdbsupport/common-exceptions.h
+++ b/gdbsupport/common-exceptions.h
@@ -26,6 +26,8 @@
 #include <string>
 #include <functional>
 
+#include "gdbsupport/underlying.h"
+
 /* Reasons for calling throw_exceptions().  NOTE: all reason values
    must be different from zero.  enum value 0 is reserved for internal
    use as the return value from an initial setjmp().  */
@@ -200,7 +202,7 @@ struct hash<gdb_exception>
 {
   size_t operator() (const gdb_exception &exc) const
   {
-    size_t result = exc.reason + exc.error;
+    size_t result = to_underlying (exc.reason) + to_underlying (exc.error);
     if (exc.message != nullptr)
       result += std::hash<std::string> {} (*exc.message);
     return result;
-- 
2.35.3