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

[Pedro Alves <pedro@palves.net>]

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.

Pedro Alves