gdb: define builtin long type to be 64 bits on amd64 Cygwin

On Windows x86-64 (when building with MinGW), the size of the "long"
type is 32 bits.  amd64_windows_init_abi therefore does:

    set_gdbarch_long_bit (gdbarch, 32);

This is also used when the chosen OS ABI is Cygwin, where the "long"
type is 64 bits.  GDB therefore gets sizeof(long) wrong when using the
builtin long type:

    $ ./gdb -nx --data-directory=data-directory -batch -ex "set architecture i386:x86-64" -ex "set osabi Cygwin" -ex "print sizeof(long)"
    The target architecture is assumed to be i386:x86-64
    $1 = 4

This patch makes GDB avoid setting the size of the long type to 32 bits
when using the Cygwin OS ABI.  it will inherit the value set in
amd64_init_abi.

With this patch, I get:

    $ ./gdb -nx --data-directory=data-directory -batch -ex "set architecture i386:x86-64" -ex "set osabi Cygwin" -ex "print sizeof(long)"
    The target architecture is assumed to be i386:x86-64
    $1 = 8

gdb/ChangeLog:

	PR gdb/21500
	* amd64-windows-tdep.c (amd64_windows_init_abi): Rename
	to...
	(amd64_windows_init_abi_common): ... this.  Don't set size of
	long type.
	(amd64_windows_init_abi): New function.
	(amd64_cygwin_init_abi): New function.
	(_initialize_amd64_windows_tdep): Use amd64_cygwin_init_abi for
	the Cygwin OS ABI.
	* i386-windows-tdep.c (_initialize_i386_windows_tdep): Clarify
	comment.

3 files changed, 32 insertions, 7 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 68c8bf7..6cb3cb5 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,19 @@
 2020-03-16  Simon Marchi  <simon.marchi@efficios.com>
 
+	PR gdb/21500
+	* amd64-windows-tdep.c (amd64_windows_init_abi): Rename
+	to...
+	(amd64_windows_init_abi_common): ... this.  Don't set size of
+	long type.
+	(amd64_windows_init_abi): New function.
+	(amd64_cygwin_init_abi): New function.
+	(_initialize_amd64_windows_tdep): Use amd64_cygwin_init_abi for
+	the Cygwin OS ABI.
+	* i386-windows-tdep.c (_initialize_i386_windows_tdep): Clarify
+	comment.
+
+2020-03-16  Simon Marchi  <simon.marchi@efficios.com>
+
 	* windows-tdep.h (is_linked_with_cygwin_dll): New declaration.
 	* windows-tdep.c (CYGWIN_DLL_NAME): New.
 	(pe_import_directory_entry): New struct type.
diff --git a/gdb/amd64-windows-tdep.c b/gdb/amd64-windows-tdep.c
index e0346f8..6d5076d 100644
--- a/gdb/amd64-windows-tdep.c
+++ b/gdb/amd64-windows-tdep.c
@@ -1209,7 +1209,7 @@ amd64_windows_auto_wide_charset (void)
 }
 
 static void
-amd64_windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+amd64_windows_init_abi_common (gdbarch_info info, struct gdbarch *gdbarch)
 {
   /* The dwarf2 unwinder (appended very early by i386_gdbarch_init) is
      preferred over the SEH one.  The reasons are:
@@ -1229,9 +1229,6 @@ amd64_windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 
   windows_init_abi (info, gdbarch);
 
-  /* On Windows, "long"s are only 32bit.  */
-  set_gdbarch_long_bit (gdbarch, 32);
-
   /* Function calls.  */
   set_gdbarch_push_dummy_call (gdbarch, amd64_windows_push_dummy_call);
   set_gdbarch_return_value (gdbarch, amd64_windows_return_value);
@@ -1244,6 +1241,21 @@ amd64_windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   set_gdbarch_auto_wide_charset (gdbarch, amd64_windows_auto_wide_charset);
 }
 
+static void
+amd64_windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+{
+  amd64_windows_init_abi_common (info, gdbarch);
+
+  /* On Windows, "long"s are only 32bit.  */
+  set_gdbarch_long_bit (gdbarch, 32);
+}
+
+static void
+amd64_cygwin_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+{
+  amd64_windows_init_abi_common (info, gdbarch);
+}
+
 static gdb_osabi
 amd64_windows_osabi_sniffer (bfd *abfd)
 {
@@ -1262,11 +1274,10 @@ void _initialize_amd64_windows_tdep ();
 void
 _initialize_amd64_windows_tdep ()
 {
-  /* The Cygwin and Windows OS ABIs are currently equivalent.  */
   gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64, GDB_OSABI_WINDOWS,
                           amd64_windows_init_abi);
   gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64, GDB_OSABI_CYGWIN,
-                          amd64_windows_init_abi);
+                          amd64_cygwin_init_abi);
 
   gdbarch_register_osabi_sniffer (bfd_arch_i386, bfd_target_coff_flavour,
 				  amd64_windows_osabi_sniffer);
diff --git a/gdb/i386-windows-tdep.c b/gdb/i386-windows-tdep.c
index bd6107b..b26731c 100644
--- a/gdb/i386-windows-tdep.c
+++ b/gdb/i386-windows-tdep.c
@@ -270,7 +270,7 @@ _initialize_i386_windows_tdep ()
   gdbarch_register_osabi_sniffer (bfd_arch_i386, bfd_target_elf_flavour,
                                   i386_cygwin_core_osabi_sniffer);
 
-  /* The Windows and Cygwin OS ABIs are currently equivalent.  */
+  /* The Windows and Cygwin OS ABIs are currently equivalent on i386.  */
   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_WINDOWS,
                           i386_windows_init_abi);
   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_CYGWIN,