Re: gdb.error: "define PI" is not a prefix command.

[Andrew Burgess <aburgess@redhat.com>]

* Simon Sobisch via Gdb <gdb@sourceware.org> [2021-12-22 16:12:11 +0100]:

> The following shows the issue quite well:
> 
> (gdb) macro define PI1 (3.1415926)
> (gdb) print PI1
> $1 = 3.1415926000000001
> (gdb) py gdb.execute("print PI1", True, False)
> $2 = 3.1415926000000001
> (gdb) py gdb.execute("macro define PI2 (3.1415926)", True, False)
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
> gdb.error: "define PI2" is not a prefix command.
> Error while executing Python code.
> (gdb) print PI2
> No symbol "PI2" in current context.
> 
> This is happening with GDB 8.2, Python 3.6.8.
> 
> It did work with GDB 7.6:
> 
> (gdb) macro define PI1 (3.1415926)
> (gdb) print PI1
> $1 = 3.1415925999999996
> (gdb) py gdb.execute("print PI1", True, False)
> $2 = 3.1415925999999996
> (gdb) py gdb.execute("macro define PI2 (3.1415926)", True, False)
> (gdb) print PI2
> $3 = 3.1415925999999996
> (gdb) py gdb.execute("print PI1", True, False)
> $24 = 3.1415925999999996
> 
> I've thought that this was related to the different python version (2.7.5 on
> GDB 7.6), but it isn't. After building GDB 11.1 on the test machine (same
> Python, obviously) it also works there.
> 
> 
> Question:
> Is there any way to execute this command with Python in GDB 8.2
> (= without upgrading GDB)?

I tried GDB 8.2.1, and the bug is fixed in this release, if a minor
update is possible then this would be the easiest solution...

Failing that I found that this works:

  (gdb) shell cat ~/tmp/file.gdb
  macro define PI2 (3.1415926)
  (gdb) py gdb.execute("source ~/tmp/file.gdb", True, False)
  (gdb) print PI2
  $1 = 3.1415926000000001

Certainly not idea, but, if you really are stuck on 8.2 then you can
write the problematic commands into a temporary file, and source that
from Python code.

There might be other hack folk come up with.

Thanks,
Andrew