[Bug bootstrap/79052] New: bootstrap-ubsan failures due to warnings

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79052

            Bug ID: 79052
           Summary: bootstrap-ubsan failures due to warnings
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: bootstrap
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

While verifying fixes for bug 79029 and bug 78608 I see the following errors
during bootstrap-ubsan (there might be others, these were just the first few
that showed up in a parallel build before it stopped).

/opt/notnfs/msebor/src/gcc/trunk/gcc/dwarf2out.c:2060:37: error: comparison
between signed and unsigned integer expressions [-Werror=sign-compare]
    gcc_assert (val1->v.val_unsigned == DWARF2_ADDR_SIZE);
/opt/notnfs/msebor/src/gcc/trunk/gcc/system.h:731:14: note: in definition of
macro ‘gcc_assert’
    ((void)(!(EXPR) ? fancy_abort (__FILE__, __LINE__, __FUNCTION__), 0 : 0))
              ^~~~
...
/opt/notnfs/msebor/src/gcc/trunk/gcc/c/gimple-parser.c: In function ‘void
c_parser_parse_gimple_body(c_parser*)’:
/opt/notnfs/msebor/src/gcc/trunk/gcc/c/gimple-parser.c:1301:34: error:
‘exp1.c_expr::value’ may be used uninitialized in this function
[-Werror=maybe-uninitialized]
    case_label = build_case_label (exp1.value, NULL_TREE,
                 ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
              decl);
              ~~~~~                
/opt/notnfs/msebor/src/gcc/trunk/gcc/c/gimple-parser.c:1283:10: note:
‘exp1.c_expr::value’ was declared here
   c_expr exp1;
          ^~~~
/opt/notnfs/msebor/src/gcc/trunk/gcc/c/gimple-parser.c:1377:49: error:
‘cond_expr.c_expr::value’ may be used uninitialized in this function
[-Werror=maybe-uninitialized]
   gimple_seq_add_stmt (seq, gimple_build_switch (cond_expr.value,
                             ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
        default_label, labels));
        ~~~~~~~~~~~~~~~~~~~~~~                    
/opt/notnfs/msebor/src/gcc/trunk/gcc/c/gimple-parser.c:1255:10: note:
‘cond_expr.c_expr::value’ was declared here
   c_expr cond_expr;
          ^~~~~~~~~
...
/opt/notnfs/msebor/src/gcc/trunk/gcc/c-family/c-cppbuiltin.c: In function ‘void
c_cpp_builtins(cpp_reader*)’:
/opt/notnfs/msebor/src/gcc/trunk/gcc/c-family/c-cppbuiltin.c:848:1: error: ‘%s’
directive argument is null [-Werror=format-length=]
 c_cpp_builtins (cpp_reader *pfile)
 ^~~~~~~~~~~~~~
...
/opt/notnfs/msebor/src/gcc/trunk/gcc/c/c-typeck.c: In function ‘char*
print_spelling(char*)’:
/opt/notnfs/msebor/src/gcc/trunk/gcc/c/c-typeck.c:7022:59: error: null
destination pointer [-Werror=format-length=]
  sprintf (d, "[" HOST_WIDE_INT_PRINT_UNSIGNED "]", p->u.i);
                                                           ^