[PATCH] malloc: Remove dumped heap support

[DJ Delorie]

Sam James <sam@gentoo.org> writes:
>> malloc_get_state is only used during the Emacs build process,
>> so we provide a stub implementation only.  Existing Emacs binaries
>> will not call this stub function, but still reference the symbol.
>
> This reassured me, but I was concerned seeing the changes below because
> of "... contained in historic Emacs executables". My modern Emacs built
> from trunk does have a .pdmp file installed at least. I don't know if
> old Emacs ever installed its (non-portable) dump, or if it was ever
> actually used for anything once installed.

It might be useful to poll the emacs mailing list for their opinions
too; they might be glad to have some external pressure to force
8-year-old emacs binary users to upgrade to something more secure.

(and it's 8-year-old emacs on 0-year-old glibc, not just older distros!)

A quick look at the emacs sources, I see a lot of #ifdef DOUG_LEA_MALLOC
so removing support might be more complicated than we think.  The
configure check is simple though:

AC_CACHE_CHECK(
  [whether malloc is Doug Lea style],
  [emacs_cv_var_doug_lea_malloc],
  [emacs_cv_var_doug_lea_malloc=no
   dnl Hooks do not work with address sanitization.
   if test "$emacs_cv_sanitize_address" != yes; then
     AC_LINK_IFELSE(
       [AC_LANG_PROGRAM(
          [[#include <malloc.h>
            static void hook (void) {}]],
          [[malloc_set_state (malloc_get_state ());
            __after_morecore_hook = hook;
            __malloc_initialize_hook = hook;]])],
       [emacs_cv_var_doug_lea_malloc=yes])
   fi])
doug_lea_malloc=$emacs_cv_var_doug_lea_malloc