gdb: fix build with newest clang

The upstream build of GDB can fail on fedora rawhide, since the self
check in regcache.c uses an unitialized variable to be compared, which
now generates the following warning:

    binutils-gdb/gdb/regcache.c:1847:42: error: variable
    'buf' is uninitialized when passed as a const pointer argument here
    [-Werror,-Wuninitialized-const-pointer]
    1847 | SELF_CHECK (regcache->raw_compare (0, &buf, register_size (inf.arch (), 0)));

This commit fixes that by initializing the variable to 0.
Since the comment above that line would be changed, it was also
reformatted so that it doesn't go beyond 80 columns.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/gdb/regcache.c b/gdb/regcache.c
index 9892c54..cf4c5dd 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -1841,9 +1841,10 @@ reg_buffer_raw_compare_zero_len_test ()
   const regcache *regcache
     = get_thread_arch_regcache (&inf, ptid_t (1, 1), inf.arch ());
 
-  /* The buffer address is irrelevant since we end up comparing 0 bytes, we just
-     need to pass something.  */
-  gdb_byte buf;
+  /* The buffer address is irrelevant since we end up comparing 0 bytes, we
+     just need to pass something.  The variable needs to be initialized to
+     avoid compiler warnings about uninitialized values.  */
+  gdb_byte buf = 0;
   SELF_CHECK (regcache->raw_compare (0, &buf, register_size (inf.arch (), 0)));
 }