Remove build system name from deterministic dumps

* configure.ac (DETERMINISTIC_DUMP): New configuration option.
* lisp/version.el (emacs-build-time): Add a comment to make the
build time deterministic if requested.
(emacs-build-system): Make variable deterministic if requested.
* src/emacs.c (main): Initialize `deterministic-dump' from the
configuration option.
(syms_of_emacs): New constant `deterministic-dump'.
* src/sysdep.c (init_system_name): Use a constant
if a deterministic dump is requested.

2 files changed, 17 insertions, 0 deletions

diff --git a/src/emacs.c b/src/emacs.c
index c512885076c..e7cb4ea4aaa 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -872,6 +872,9 @@ main (int argc, char **argv)
   SET_BINARY (fileno (stdout));
 #endif /* MSDOS */
 
+  if (DETERMINISTIC_DUMP)
+    Vdeterministic_dump = Qt;
+
   /* Skip initial setlocale if LC_ALL is "C", as it's not needed in that case.
      The build procedure uses this while dumping, to ensure that the
      dumped Emacs does not have its system locale tables initialized,
@@ -2532,6 +2535,13 @@ libraries; only those already known by Emacs will be loaded.  */);
   Vdynamic_library_alist = Qnil;
   Fput (intern_c_string ("dynamic-library-alist"), Qrisky_local_variable, Qt);
 
+  DEFVAR_BOOL ("deterministic-dump", Vdeterministic_dump,
+    doc: /* If non-nil, attempt to make dumping deterministic by
+avoiding sources of nondeterminism such as absolute file names, the
+hostname, or timestamps.  */);
+  Vdeterministic_dump = DETERMINISTIC_DUMP ? Qt : Qnil;
+  XSYMBOL (intern_c_string ("deterministic-dump"))->constant = 1;
+
 #ifdef WINDOWSNT
   Vlibrary_cache = Qnil;
   staticpro (&Vlibrary_cache);
diff --git a/src/sysdep.c b/src/sysdep.c
index 418c50d5e78..b01c64d52ac 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -1408,6 +1408,13 @@ setup_pty (int fd)
 void
 init_system_name (void)
 {
+  if (DETERMINISTIC_DUMP && (might_dump || ! NILP (Vpurify_flag)))
+    {
+      /* If we're dumping, set the hostname to a literal so that the
+         dump is deterministic.  */
+      Vsystem_name = build_pure_c_string ("elided");
+      return;
+    }
   char *hostname_alloc = NULL;
   char *hostname;
 #ifndef HAVE_GETHOSTNAME