cache.c: make all io-related functions return errno on error

We'll need proper return-values from these functions to make the cache
behave correctly (which includes giving proper error messages).

Noticed-by: Jim Meyering <jim@meyering.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 24 insertions, 9 deletions

diff --git a/cache.c b/cache.c
index add647e..6847202 100644
--- a/cache.c
+++ b/cache.c
@@ -57,30 +57,34 @@ static int open_slot(struct cache_slot *slot)
 
         bufz = memchr(slot->buf, 0, slot->bufsize);
         if (bufz)
                 bufkeylen = bufz - slot->buf;
 
         slot->match = bufkeylen == slot->keylen &&
             !memcmp(slot->key, slot->buf, bufkeylen + 1);
 
         return 0;
 }
 
 /* Close the active cache slot */
-static void close_slot(struct cache_slot *slot)
+static int close_slot(struct cache_slot *slot)
 {
+        int err = 0;
         if (slot->cache_fd > 0) {
-                close(slot->cache_fd);
-                slot->cache_fd = -1;
+                if (close(slot->cache_fd))
+                        err = errno;
+                else
+                        slot->cache_fd = -1;
         }
+        return err;
 }
 
 /* Print the content of the active cache slot (but skip the key). */
 static int print_slot(struct cache_slot *slot)
 {
         ssize_t i, j = 0;
 
         i = lseek(slot->cache_fd, slot->keylen + 1, SEEK_SET);
         if (i != slot->keylen + 1)
                 return errno;
 
         while((i=read(slot->cache_fd, slot->buf, sizeof(slot->buf))) > 0)
@@ -107,59 +111,68 @@ static int is_expired(struct cache_slot *slot)
 static int is_modified(struct cache_slot *slot)
 {
         struct stat st;
 
         if (stat(slot->cache_name, &st))
                 return 1;
         return (st.st_ino != slot->cache_st.st_ino ||
                 st.st_mtime != slot->cache_st.st_mtime ||
                 st.st_size != slot->cache_st.st_size);
 }
 
 /* Close an open lockfile */
-static void close_lock(struct cache_slot *slot)
+static int close_lock(struct cache_slot *slot)
 {
+        int err = 0;
         if (slot->lock_fd > 0) {
-                close(slot->lock_fd);
-                slot->lock_fd = -1;
+                if (close(slot->lock_fd))
+                        err = errno;
+                else
+                        slot->lock_fd = -1;
         }
+        return err;
 }
 
 /* Create a lockfile used to store the generated content for a cache
  * slot, and write the slot key + \0 into it.
  * Returns 0 on success and errno otherwise.
  */
 static int lock_slot(struct cache_slot *slot)
 {
         slot->lock_fd = open(slot->lock_name, O_RDWR|O_CREAT|O_EXCL,
                              S_IRUSR|S_IWUSR);
         if (slot->lock_fd == -1)
                 return errno;
-        write(slot->lock_fd, slot->key, slot->keylen + 1);
+        if (write(slot->lock_fd, slot->key, slot->keylen + 1) < 0)
+                return errno;
         return 0;
 }
 
 /* Release the current lockfile. If `replace_old_slot` is set the
  * lockfile replaces the old cache slot, otherwise the lockfile is
  * just deleted.
  */
 static int unlock_slot(struct cache_slot *slot, int replace_old_slot)
 {
         int err;
 
         if (replace_old_slot)
                 err = rename(slot->lock_name, slot->cache_name);
         else
                 err = unlink(slot->lock_name);
-        return err;
+
+        if (err)
+                return errno;
+
+        return 0;
 }
 
 /* Generate the content for the current cache slot by redirecting
  * stdout to the lock-fd and invoking the callback function
  */
 static int fill_slot(struct cache_slot *slot)
 {
         int tmp;
 
         /* Preserve stdout */
         tmp = dup(STDOUT_FILENO);
         if (tmp == -1)
@@ -168,25 +181,27 @@ static int fill_slot(struct cache_slot *slot)
         /* Redirect stdout to lockfile */
         if (dup2(slot->lock_fd, STDOUT_FILENO) == -1)
                 return errno;
 
         /* Generate cache content */
         slot->fn(slot->cbdata);
 
         /* Restore stdout */
         if (dup2(tmp, STDOUT_FILENO) == -1)
                 return errno;
 
         /* Close the temporary filedescriptor */
-        close(tmp);
+        if (close(tmp))
+                return errno;
+
         return 0;
 }
 
 /* Crude implementation of 32-bit FNV-1 hash algorithm,
  * see http://www.isthe.com/chongo/tech/comp/fnv/ for details
  * about the magic numbers.
  */
 #define FNV_OFFSET 0x811c9dc5
 #define FNV_PRIME  0x01000193
 
 unsigned long hash_str(const char *str)
 {