[gcc r12-825] Avoid outputting corrupt string constructor when host/target chars mismatch.

[Joern Rennecke <amylaar@gcc.gnu.org>]

https://gcc.gnu.org/g:a8e19fa4198ea2504c89d01741d11766e0e9e91b

commit r12-825-ga8e19fa4198ea2504c89d01741d11766e0e9e91b
Author: Joern Rennecke <joern.rennecke@embecosm.com>
Date:   Mon May 17 10:57:23 2021 +0100

    Avoid outputting corrupt string constructor when host/target chars mismatch.
    
            * c-common.c (braced_list_to_string): Return CTOR unchanged
            if host and target character sizes don't match.

Diff:
---
 gcc/c-family/c-common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 7bd799d1825..b7daa2e2654 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -9059,6 +9059,12 @@ braced_list_to_string (tree type, tree ctor, bool member)
   if (!member && !tree_fits_uhwi_p (typesize))
     return ctor;
 
+  /* If the target char size differes from the host char size, we'd risk
+     loosing data and getting object sizes wrong by converting to
+     host chars.  */
+  if (TYPE_PRECISION (char_type_node) != CHAR_BIT)
+    return ctor;
+
   /* If the array has an explicit bound, use it to constrain the size
      of the string.  If it doesn't, be sure to create a string that's
      as long as implied by the index of the last zero specified via