[gdb/testsuite] Add gdb.python/py-disasm-{exec,obj}.exp

I tried to reproduce a problem in test-case gdb.python/py-disasm.exp on a
s390x machine, but when running with target board unix/-m31 I saw that the
required libraries were missing, so I couldn't generate an executable.

However, I realized that I did have an object file, and the test-case should
mostly also work with an object file.

I've renamed gdb.python/py-disasm.exp to gdb.python/py-disasm.exp.tcl and
included it from two new minimal test-case wrappers:
- gdb.python/py-disasm-exec.exp, and
- gdb.python/py-disasm-obj.exp
where the former uses an executable as before, and the latter uses an object
file.

Using an object file required changing the info.read_memory calls in
gdb.python/py-disasm.py:
...
-            info.read_memory(1, -info.address + 2)
+            info.read_memory(1, -info.address - 1)
...
because reading from address 2 succeeds.  Using address -1 instead does
generate the expected gdb.MemoryError.

Tested on x86_64-linux.

1 files changed, 4 insertions, 4 deletions

diff --git a/gdb/testsuite/gdb.python/py-disasm.py b/gdb/testsuite/gdb.python/py-disasm.py
index 2741fdb..f105657 100644
--- a/gdb/testsuite/gdb.python/py-disasm.py
+++ b/gdb/testsuite/gdb.python/py-disasm.py
@@ -252,7 +252,7 @@ class MemoryErrorEarlyDisassembler(TestDisassembler):
     def disassemble(self, info):
         tag = "## FAIL"
         try:
-            info.read_memory(1, -info.address + 2)
+            info.read_memory(1, -info.address - 1)
         except gdb.MemoryError:
             tag = "## AFTER ERROR"
         result = builtin_disassemble_wrapper(info)
@@ -267,7 +267,7 @@ class MemoryErrorLateDisassembler(TestDisassembler):
     def disassemble(self, info):
         result = builtin_disassemble_wrapper(info)
         # The following read will throw an error.
-        info.read_memory(1, -info.address + 2)
+        info.read_memory(1, -info.address - 1)
         return DisassemblerResult(1, "BAD")
 
 
@@ -276,9 +276,9 @@ class RethrowMemoryErrorDisassembler(TestDisassembler):
 
     def disassemble(self, info):
         try:
-            info.read_memory(1, -info.address + 2)
+            info.read_memory(1, -info.address - 1)
         except gdb.MemoryError as e:
-            raise gdb.MemoryError("cannot read code at address 0x2")
+            raise gdb.MemoryError("cannot read code at address -1")
         return DisassemblerResult(1, "BAD")