[PATCH] gdb: only include mips and riscv targets if building with 64-bit bfd

[Andrew Burgess]

While testing another patch I was trying to build different
configurations of GDB, and, during one test build I ran into a
problem, I configured with `--enable-targets=all
--host=i686-w64-mingw32` and saw this error while linking GDB:

  .../i686-w64-mingw32/bin/ld: mips-tdep.o: in function `mips_gdbarch_init':
  .../src/gdb/mips-tdep.c:8730: undefined reference to `disassembler_options_mips'
  .../i686-w64-mingw32/bin/ld: riscv-tdep.o: in function `riscv_gdbarch_init':
  .../src/gdb/riscv-tdep.c:3851: undefined reference to `disassembler_options_riscv'

So the `disassembler_options_mips` and `disassembler_options_riscv`
symbols are missing.

This turns out to be because mips-dis.c and riscv-dis.c, in which
these symbols are defined, are in the TARGET64_LIBOPCODES_CFILES list
in opcodes/Makefile.am, these files are only built when we are
building with a 64-bit bfd.

If we look further, into bfd/Makefile.am, we can see that all the
files matching elf*-riscv.lo are in the BFD64_BACKENDS list, as are
the elf*-mips.lo files, and (I know because I tried), the two
disassemblers do, not surprisingly, depend on features supplied from
libbfd.

So, though we can build most of GDB just fine for riscv and mips with
a 32-bit bfd, if I understand correctly, the final GDB
executable (assuming we could get it to link) would not understand
these architectures at the bfd level, nor would there be any
disassembler available.  This sounds like a pretty useless GDB to me.

So, in this commit, I move the riscv and mips targets into GDB's list
of targets that require a 64-bit bfd.  After this I can build GDB just
fine with the configure options given above.
---
 gdb/Makefile.in | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index bff27577b95..f2966cf6c00 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -710,10 +710,21 @@ ALL_64_TARGET_OBS = \
 	arch/aarch64-insn.o \
 	arch/aarch64-mte-linux.o \
 	arch/amd64.o \
+	arch/riscv.o \
 	ia64-linux-tdep.o \
 	ia64-tdep.o \
 	ia64-vms-tdep.o \
+	mips-fbsd-tdep.o \
+	mips-linux-tdep.o \
+	mips-netbsd-tdep.o \
+	mips-sde-tdep.o \
+	mips-tdep.o \
 	mips64-obsd-tdep.o \
+	riscv-fbsd-tdep.o \
+	riscv-linux-tdep.o \
+	riscv-none-tdep.o \
+	riscv-ravenscar-thread.o \
+	riscv-tdep.o \
 	sparc64-fbsd-tdep.o \
 	sparc64-linux-tdep.o \
 	sparc64-netbsd-tdep.o \
@@ -734,7 +745,6 @@ ALL_TARGET_OBS = \
 	arch/arm-linux.o \
 	arch/i386.o \
 	arch/ppc-linux-common.o \
-	arch/riscv.o \
 	arm-bsd-tdep.o \
 	arm-fbsd-tdep.o \
 	arm-linux-tdep.o \
@@ -793,11 +803,6 @@ ALL_TARGET_OBS = \
 	mep-tdep.o \
 	microblaze-linux-tdep.o \
 	microblaze-tdep.o \
-	mips-fbsd-tdep.o \
-	mips-linux-tdep.o \
-	mips-netbsd-tdep.o \
-	mips-sde-tdep.o \
-	mips-tdep.o \
 	mn10300-linux-tdep.o \
 	mn10300-tdep.o \
 	moxie-tdep.o \
@@ -818,11 +823,6 @@ ALL_TARGET_OBS = \
 	ppc-sysv-tdep.o \
 	ppc64-tdep.o \
 	ravenscar-thread.o \
-	riscv-fbsd-tdep.o \
-	riscv-linux-tdep.o \
-	riscv-none-tdep.o \
-	riscv-ravenscar-thread.o \
-	riscv-tdep.o \
 	rl78-tdep.o \
 	rs6000-aix-tdep.o \
 	rs6000-lynx178-tdep.o \
-- 
2.25.4