5 files changed, 72 insertions, 0 deletions
diff --git a/src/include/s6-rc/s6rc-utils.h b/src/include/s6-rc/s6rc-utils.h
index 15a3b74..e453ade 100644
--- a/src/include/s6-rc/s6rc-utils.h
+++ b/src/include/s6-rc/s6rc-utils.h
@@ -24,4 +24,7 @@ extern int s6rc_livedir_canon (char const **) ;
 extern int s6rc_live_state_size (char const *, uint32_t *, uint32_t *) ;
 extern int s6rc_live_state_read (char const *, unsigned char *, uint32_t) ;
 
+extern uint32_t s6rc_get_major (char const *) ;  /* always pass S6RC_VERSION */
+extern uint32_t s6rc_read_major (char const *) ; /* the major a db was compiled with */
+
 #endif
diff --git a/src/libs6rc/deps-lib/s6rc b/src/libs6rc/deps-lib/s6rc
index f1a8370..c16ccdf 100644
--- a/src/libs6rc/deps-lib/s6rc
+++ b/src/libs6rc/deps-lib/s6rc
@@ -4,6 +4,7 @@ s6rc_db_check_revdeps.o
 s6rc_db_read.o
 s6rc_db_read_sizes.o
 s6rc_db_read_uint32.o
+s6rc_get_major.o
 s6rc_graph_closure.o
 s6rc_graph_clean.o
 s6rc_live_state_size.o
@@ -13,6 +14,7 @@ s6rc_livedir_create.o
 s6rc_livedir_prefix.o
 s6rc_livedir_prefixsize.o
 s6rc_lock.o
+s6rc_read_major.o
 s6rc_read_uint.o
 s6rc_sanitize_dir.o
 s6rc_servicedir_internal.o
diff --git a/src/libs6rc/s6rc_get_major.c b/src/libs6rc/s6rc_get_major.c
new file mode 100644
index 0000000..3bb9fb1
--- /dev/null
+++ b/src/libs6rc/s6rc_get_major.c
@@ -0,0 +1,21 @@
+/* ISC license. */
+
+#include <stdint.h>
+
+#include <skalibs/uint16.h>
+
+#include <s6-rc/s6rc-utils.h>
+
+uint32_t s6rc_get_major (char const *s)
+{
+  size_t len = 0, l ;
+  uint32_t acc = 0 ;
+  uint16_t u ;
+  l = uint16_scan(s + len, &u) ;
+  if (!l || s[len + l++] != '.') return 0 ;
+  len += l ; acc = acc << 16 | u ;
+  l = uint16_scan(s + len, &u) ;
+  if (!l || s[len + l++] != '.') return 0 ;
+  len += l ; acc = acc << 16 | u ;
+  return acc ;
+}
diff --git a/src/libs6rc/s6rc_read_major.c b/src/libs6rc/s6rc_read_major.c
new file mode 100644
index 0000000..978f29c
--- /dev/null
+++ b/src/libs6rc/s6rc_read_major.c
@@ -0,0 +1,30 @@
+/* ISC license. */
+
+#include <string.h>
+#include <stdint.h>
+#include <errno.h>
+
+#include <skalibs/uint32.h>
+#include <skalibs/djbunix.h>
+
+#include <s6-rc/s6rc-utils.h>
+
+#include <skalibs/posixishard.h>
+
+uint32_t s6rc_read_major (char const *compiled)
+{
+  size_t clen = strlen(compiled) ;
+  ssize_t r ;
+  uint32_t res ;
+  char tmp[UINT32_FMT] ;
+  char fn[clen + 7] ;
+  memcpy(fn, compiled, clen) ;
+  memcpy(fn + clen, "/major", 7) ;
+  r = openreadnclose(fn, tmp, UINT32_FMT) ;
+  if (r == -1) return errno == ENOENT ? 6 : 0 ; /* up to 0.6.x.y doesn't have db/major */
+  if (!r) return 0 ;
+  if (tmp[r] != '\n') return (errno = EPROTO, 0) ;
+  tmp[r] = 0 ;
+  if (uint320_scan(tmp, &res) != r) return (errno = EPROTO, 0) ;
+  return res ;
+}
diff --git a/src/s6-rc/s6-rc-compile.c b/src/s6-rc/s6-rc-compile.c
index 62b9aef..0d4e208 100644
--- a/src/s6-rc/s6-rc-compile.c
+++ b/src/s6-rc/s6-rc-compile.c
@@ -1573,6 +1573,21 @@ static inline void write_db (char const *compiled, s6rc_db_t const *db)
   strerr_diefusys(111, "write to ", dbfn) ;
 }
 
+static inline void write_major (char const *compiled)
+{
+  uint32_t version = s6rc_get_major(S6RC_VERSION) ;
+  size_t len ;
+  char fmt[UINT32_FMT] ;
+  if (!version)
+  {
+    cleanup(compiled) ;
+    strerr_dief(101, "invalid software version: ", S6RC_VERSION) ;
+  }
+  len = uint32_fmt(fmt, version) ;
+  fmt[len++] = '\n' ;
+  auto_file(compiled, "major", fmt, len) ;
+}
+
 static inline void write_compiled (
   char const *compiled,
   s6rc_db_t const *db,
@@ -1585,6 +1600,7 @@ static inline void write_compiled (
 {
   if (verbosity >= 2) strerr_warni("writing compiled information to ", compiled) ;
   init_compiled(compiled) ;
+  write_major(compiled) ;
   write_sizes(compiled, db) ;
   write_resolve(compiled, db, bundles, nbundles, bdeps) ;
   stralloc_free(&data) ;