[gcc r13-2958] Robustify DWARF2_UNWIND_INFO handling in vx-common.h

[Olivier Hainque]

https://gcc.gnu.org/g:2813f529ab8df6daef739d996688caab615eb1a9

commit r13-2958-g2813f529ab8df6daef739d996688caab615eb1a9
Author: Olivier Hainque <hainque@adacore.com>
Date:   Thu Mar 10 10:46:19 2022 +0000

    Robustify DWARF2_UNWIND_INFO handling in vx-common.h
    
    This adjusts vx-common.h to #define DWARF2_UNWIND_INFO to 0
    when ARM_UNWIND_INFO is set, preventing defaults.h from
    possibly setting DWARF2_UNWIND_INFO to 1 (as well) on its own
    afterwards if the macro isn't defined.
    
    2022-09-29  Olivier Hainque  <hainque@adacore.com>
    
    gcc/
            * config/vx-common.h (DWARF2_UNWIND_INFO): #define to 0
            when ARM_UNWIND_INFO is set.

Diff:
---
 gcc/config/vx-common.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/gcc/config/vx-common.h b/gcc/config/vx-common.h
index bc27684375a..bf5823af6bf 100644
--- a/gcc/config/vx-common.h
+++ b/gcc/config/vx-common.h
@@ -74,7 +74,8 @@ along with GCC; see the file COPYING3.  If not see
 /* ---------------------- Debug and unwind info formats ------------------  */
 
 /* Dwarf2 unwind info is supported, unless overriden by a request for a target
-   specific format.
+   specific format.  Always #define DWARF2_UNWIND_INFO to prevent defaults.h
+   from picking a possibly different value.
 
    Taking care of this here allows using DWARF2_UNWIND_INFO in #if conditions
    from the common config/vxworks.h files, included before the cpu
@@ -84,8 +85,10 @@ along with GCC; see the file COPYING3.  If not see
    #if point.  Since <cpu>/vxworks.h. is typically included after
    config/vxworks.h, #if expressions in the latter can't rely on possible
    redefinitions in the former.  */
-#if !ARM_UNWIND_INFO
 #undef DWARF2_UNWIND_INFO
+#if ARM_UNWIND_INFO
+#define DWARF2_UNWIND_INFO 0
+#else
 #define DWARF2_UNWIND_INFO 1
 #endif