Add the magic number to the dependency record.

The magic number will be used later to determine if a target has already
been rebuild.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/build.c b/src/build.c
index 73fc757..d217a23 100644
--- a/src/build.c
+++ b/src/build.c
@@ -285,8 +285,8 @@ void add_dep(const char *target, int indent) {
             fp = fopen(dep_path, "w");
             if (!fp)
                 fatal(ERRM_FOPEN, dep_path);
-            /* skip the first n bytes that are reserved for the hash */
-            fseek(fp, 20, SEEK_SET);
+            /* skip the first n bytes that are reserved for the hash + magic number */
+            fseek(fp, 20 + sizeof(unsigned int), SEEK_SET);
         } else {
             fatal(ERRM_FOPEN, dep_path);
         }
@@ -329,7 +329,9 @@ void hash_file(const char *target, unsigned char (*hash)[20]) {
 
 /* Calculate and store the hash of target in the right dependency file */
 void write_dep_hash(const char *target) {
+    assert(getenv("REDO_MAGIC"));
     unsigned char hash[SHA_DIGEST_LENGTH];
+    int magic = atoi(getenv("REDO_MAGIC"));
 
     hash_file(target, &hash);
 
@@ -341,6 +343,9 @@ void write_dep_hash(const char *target) {
     if (write(out, hash, sizeof hash) < (ssize_t) sizeof hash)
         fatal("redo: failed to write hash to '%s'", dep_path);
 
+    if (write(out, &magic, sizeof(unsigned int)) < (ssize_t) sizeof(unsigned int))
+        fatal("redo: failed to write magic number to '%s'", dep_path);
+
     if (close(out))
         fatal("redo: failed to close file descriptor.");
     free(dep_path);