[PATCH] Objective-C: don't require redundant -fno-objc-sjlj-exceptions for the NeXT v2 ABI

[Matt Jacobson via Gcc-patches]

As is, an invocation of GCC with -fnext-runtime -fobjc-abi-version=2 crashes, 
unless target-specific code adds an implicit -fno-objc-sjlj-exceptions (which 
Darwin does).

This patch makes the general case not crash.

I don't have commit access, so if this patch is suitable, I'd need someone else
to commit it for me.  Thanks.

gcc/objc/ChangeLog:

2021-07-28  Matt Jacobson  <mhjacob...@me.com>

        * objc-next-runtime-abi-02.c (objc_next_runtime_abi_02_init): Warn
        about and reset flag_objc_sjlj_exceptions regardless of
        flag_objc_exceptions.


gcc/c-family/ChangeLog:

2021-07-28  Matt Jacobson  <mhjacob...@me.com>

        * c-opts.c (c_common_post_options): Default to
        flag_objc_sjlj_exceptions = 1 only when flag_objc_abi < 2.

diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index c51d6d34726..2568df67972 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -840,9 +840,9 @@ c_common_post_options (const char **pfilename)
   else if (!flag_gnu89_inline && !flag_isoc99)
     error ("%<-fno-gnu89-inline%> is only supported in GNU99 or C99 mode");
 
-  /* Default to ObjC sjlj exception handling if NeXT runtime.  */
+  /* Default to ObjC sjlj exception handling if NeXT <v2 runtime.  */
   if (flag_objc_sjlj_exceptions < 0)
-    flag_objc_sjlj_exceptions = flag_next_runtime;
+    flag_objc_sjlj_exceptions = (flag_next_runtime && flag_objc_abi < 2);
   if (flag_objc_exceptions && !flag_objc_sjlj_exceptions)
     flag_exceptions = 1;
 
diff --git a/gcc/objc/objc-next-runtime-abi-02.c 
b/gcc/objc/objc-next-runtime-abi-02.c
index 66c13ad0db2..9a0868410a8 100644
--- a/gcc/objc/objc-next-runtime-abi-02.c
+++ b/gcc/objc/objc-next-runtime-abi-02.c
@@ -245,7 +245,7 @@ objc_next_runtime_abi_02_init (objc_runtime_hooks *rthooks)
 {
   extern_names = ggc_cleared_vec_alloc<hash> (SIZEHASHTABLE);
 
-  if (flag_objc_exceptions && flag_objc_sjlj_exceptions)
+  if (flag_objc_sjlj_exceptions)
     {
       inform (UNKNOWN_LOCATION,
              "%<-fobjc-sjlj-exceptions%> is ignored for "