[gcc r14-9760] libiberty: Invoke D demangler when --format=auto

[Tom Tromey <tromey@gcc.gnu.org>]

https://gcc.gnu.org/g:ca2f7c84927f85b95f0f48f82b93f1460c372db4

commit r14-9760-gca2f7c84927f85b95f0f48f82b93f1460c372db4
Author: Tom Tromey <tom@tromey.com>
Date:   Sat Mar 30 13:48:30 2024 -0600

    libiberty: Invoke D demangler when --format=auto
    
    Investigating GDB PR d/31580 showed that the libiberty demangler
    doesn't automatically demangle D mangled names.  However, I think it
    should -- like C++ and Rust (new-style), D mangled names are readily
    distinguished by the leading "_D", and so the likelihood of confusion
    is low.  The other non-"auto" cases in this code are Ada (where the
    encoded form could more easily be confused by ordinary programs) and
    Java (which is long gone, but which also shared the C++ mangling and
    thus was just an output style preference).
    
    This patch also fixed another GDB bug, though of course that part
    won't apply to the GCC repository.
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31580
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30276
    
    libiberty
            * cplus-dem.c (cplus_demangle): Try the D demangler with
            "auto" format.
            * testsuite/d-demangle-expected: Add --format=auto test.

Diff:
---
 libiberty/cplus-dem.c                   | 2 +-
 libiberty/testsuite/d-demangle-expected | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/libiberty/cplus-dem.c b/libiberty/cplus-dem.c
index 8b92946981f..ee9e84f5d6b 100644
--- a/libiberty/cplus-dem.c
+++ b/libiberty/cplus-dem.c
@@ -186,7 +186,7 @@ cplus_demangle (const char *mangled, int options)
   if (GNAT_DEMANGLING)
     return ada_demangle (mangled, options);
 
-  if (DLANG_DEMANGLING)
+  if (DLANG_DEMANGLING || AUTO_DEMANGLING)
     {
       ret = dlang_demangle (mangled, options);
       if (ret)
diff --git a/libiberty/testsuite/d-demangle-expected b/libiberty/testsuite/d-demangle-expected
index 47b059c4298..cfbdf2a52cb 100644
--- a/libiberty/testsuite/d-demangle-expected
+++ b/libiberty/testsuite/d-demangle-expected
@@ -1470,3 +1470,8 @@ demangle.anonymous
 --format=dlang
 _D8demangle9anonymous03fooZ
 demangle.anonymous.foo
+#
+# Test that 'auto' works.
+--format=auto
+_D8demangle9anonymous03fooZ
+demangle.anonymous.foo