[Bug bootstrap/63888] New: [5 Regression] bootstrap failed when configured with -with-build-config=bootstrap-asan --disable-werror

["hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63888

            Bug ID: 63888
           Summary: [5 Regression] bootstrap failed when configured with
                    -with-build-config=bootstrap-asan --disable-werror
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: bootstrap
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com

On Linux/x86-64, r217602 gave

build/genmddeps /export/gnu/import/git/sources/gcc/gcc/common.md
/export/gnu/import/git/sources/gcc/gcc/config/i386/i386.md > tmp-mddeps
build/genmodes -h > tmp-modes.h

=================================================================
==31507==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x47b5da in __interceptor_malloc
/export/gnu/import/git/sources/gcc/libsanitizer/asan/asan_malloc_linux.cc:38
    #1 0x4b42d7 in xmalloc
/export/gnu/import/git/sources/gcc/libiberty/xmalloc.c:147

SUMMARY: AddressSanitizer: 40 byte(s) leaked in 1 allocation(s).
make[5]: *** [s-mddeps] Error 23

There are some global string variables initialized with

Breakpoint 5, xmalloc (size=size@entry=40)
    at /export/gnu/import/git/sources/gcc/libiberty/xmalloc.c:146
146        size = 1;
(gdb) bt
#0  xmalloc (size=size@entry=40)
    at /export/gnu/import/git/sources/gcc/libiberty/xmalloc.c:146
#1  0x00000000004b43d1 in xstrndup (
    s=0x7fffffffe18a "/export/gnu/import/git/sources/gcc/gcc/common.md", 
    n=<optimized out>)
    at /export/gnu/import/git/sources/gcc/libiberty/xstrndup.c:56
#2  0x00000000004aff9e in handle_toplevel_file (
    handle_directive=handle_directive@entry=0x0)
    at /export/gnu/import/git/sources/gcc/gcc/read-md.c:1008
#3  0x00000000004b0672 in read_md_files (argc=<optimized out>, 
    argv=<optimized out>, parse_opt=parse_opt@entry=0x0, 
    handle_directive=handle_directive@entry=0x0)
    at /export/gnu/import/git/sources/gcc/gcc/read-md.c:1138
#4  0x00000000004059d1 in main (argc=<optimized out>, argv=<optimized out>)
    at /export/gnu/import/git/sources/gcc/gcc/genmddeps.c:50
(gdb) c

They aren't freed before exit and are detected as memory leaks.
How can they be suppressed?