Re: Question Regarding Int Cast Error in GDB Python

[Luis via Gdb <gdb@sourceware.org>]

On 8/22/25 19:21, Vacha Bhavsar via Gdb wrote:
> Hi,
> 
> I am developing a patch for QEMU which would allow QEMU to expose
> SME registers, such as the ZA storage, via gdbstub to a remote
> gdb client session. I am working to write a simple test case for
> this change which simply sets the value of the za register, then
> reads it and ensures what is read is equivalent to what was set.
> 
> The full test case can be found here:
> 
> https://lists.gnu.org/archive/html/qemu-devel/2025-08/msg01815.html
> 
> However, it seems there is an issue in the int cast in the following
> code:
> 
> v = gdb.parse_and_eval(reg)
> report(str(v.type) == "uint8_t", "size of %s" % (reg))
> report(int(v) == 0x1, "%s is 0x%x" % (reg, 0x1))

If reg is ZA, I´d expect gdb to have difficulties casting the whole 
array to an int, hence the message about not managing to operate on 
integers larger than 8 bytes.

How are you testing ZA? Byte by byte?

> 
> This results in the following error:
> 
> Python Exception <class 'gdb.error'>: That operation is not available
> on integers of more than 8 bytes.
> Error occurred in Python: That operation is not available on integers
> of more than 8 bytes.
> 
> After running various tests with different host architectures, gdb
> versions, python version and int casting included and excluded, we
> are seeing that this issue only seems to arise when the int cast is
> included and the gdb used is GNU gdb (Ubuntu 15.0.50.20240403-0ubuntu1)
> 15.0.50.20240403-git (regardless of python version and host architecture).
> 
> The test results are presented below. I was hoping to get some guidance
> regarding this error and what may be the cause if it indeed stems from
> this specific version of gdb?
> 
> Thanks,
> Vacha
> 
> 
>   gdb     gdb target           python   host          int cast    status
> version support              version  architecture
> 16.3 --enable-targets=all 3.11.13   x86        yes        pass
> 16.3 --enable-targets=all 3.11.13   x86         no        pass
> 16.3 --enable-targets=all 3.10.18   x86        yes        pass
> 16.3 --enable-targets=all 3.10.18   x86         no        pass
> 16.3 --enable-targets=all 3.8.10    x86        yes        pass
> 16.3 --enable-targets=all 3.8.10    x86          no        pass
> 
> 16.3   aarch64             3.11.0rc1 aarch64      yes        pass
> 16.3   aarch64             3.11.0rc1 aarch64       no        pass
> 16.3   aarch64             3.10.12   aarch64      yes        pass
> 16.3   aarch64             3.10.12   aarch64       no        pass
> 
> 15.0   multiarch           3.10.12   aarch64      yes        fail
> 15.0   multiarch           3.10.12   aarch64      no        pass
> 15.0   multiarch          3.11.0rc1 aarch64      yes        fail
> 15.0   multiarch          3.11.0rc1 aarch64      no        pass
> 
> 15.0   multiarch          3.8.10      x86            yes        fail
> 15.0   multiarch          3.8.10      x86             no        pass
> 15.0   multiarch        3.11.13      x86            yes        fail
> 15.0   multiarch        3.11.13      x86             no        pass
> 15.0   multiarch        3.10.18      x86            yes        fail
> 15.0   multiarch        3.10.18     x86             no        pass