Re: [PATCH 3/4] gdb: distinguish GNU and MSVC flavors of the Windows OS ABI

[Simon Marchi <simark@simark.ca>]

On 7/15/26 10:10 AM, Pedro Alves wrote:
> On 2026-07-15 14:13, Simon Marchi wrote:
>> On 7/15/26 7:18 AM, Pedro Alves wrote:
>>> On 2026-07-15 02:21, Simon Marchi wrote:
>>>> What happens if you build a GDB with --enable-targets=all and load a
>>>> .exe?  Is either ABI preferred over the other?  
>>>
>>> The preferred one is taken out of --target, defaults to GNU.
>>> --enable-targets=foo,bar,all does not affect it.
>>
>> I was thinking when building GDB on Linux (with --target that defaults
>> to something Linux) with --enable-targets=all, i.e. a typical
>> development build.  In that case, the --target does not help to choose
>> an ABI, so the fallback must come from somewhere else.
>>
> 
> Hmm, I _think_ I see what the confusion is.  The logic is:
> 
>   "let GDB pick the flavor": GDB uses the configured default OS ABI (from --target) when that is a Windows flavor, and otherwise assumes the GNU flavor."
>                                                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> 
> The code that does this is here:
> 
> +  /* A generic "Windows" OS ABI means a PE binary whose flavor --
> +     GNU (MinGW) or MSVC -- could not be determined.  The osabi
> +     sniffers and gdbserver's target description both report the
> +     generic "Windows" OS ABI, because neither can tell the two
> +     flavors apart from the binary alone.  Resolve it here to a
> +     concrete flavor: use the configured default if that is itself a
> +     Windows flavor, otherwise assume GNU.  */
> +  if (info->osabi == GDB_OSABI_WINDOWS)
> +    {
> +      info->osabi = GDB_OSABI_WINDOWS_GNU;       <<< "somewhere else"
> +#ifdef GDB_OSABI_DEFAULT
> +      if (GDB_OSABI_DEFAULT == GDB_OSABI_WINDOWS_GNU
> +         || GDB_OSABI_DEFAULT == GDB_OSABI_WINDOWS_MSVC)
> +       info->osabi = GDB_OSABI_DEFAULT;
> +#endif
> +    }
> 
> So with --target=Linux, if the sniffer, or the target.xml, or the user picks/returns
> GDB_OSABI_WINDOWS, we resolve to GDB_OSABI_WINDOWS_GNU, as GDB_OSABI_DEFAULT itself is not
> a Windows flavor (it's GDB_OSABI_LINUX).
> 
> Does this clarify it?  The "somewhere else" is basically indicated above in the <<< line.

Ah yes thanks, I had missed the "and otherwise assumes the GNU flavor".

Simon