[systemd-devel] [PATCH] util: fix strict aliasing violations in use of struct inotify_event v5

[Shawn Paul Landden]

There is alot of cleanup that will have to happen to turn on
-fstrict-aliasing, but I think our code should be correct to the rule.
---
 src/core/mount.c |  4 ++--
 src/core/path.c  |  4 ++--
 src/journal/sd-journal.c |  4 ++--
 src/shared/util.c|  5 ++---
 src/shared/util.h| 10 --
 src/udev/udevd.c |  4 ++--
 6 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/src/core/mount.c b/src/core/mount.c
index f8731bb..18ee2a0 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -1701,11 +1701,11 @@ static int mount_dispatch_io(sd_event_source *source, 
int fd, uint32_t revents,
  * internal behaviour of libmount here. */
 
 for (;;) {
-uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct 
inotify_event);
+inotify_event_buffer_t buffer;
 struct inotify_event *e;
 ssize_t l;
 
-l = read(fd, buffer, sizeof(buffer));
+l = read(fd, buffer.raw, sizeof(buffer.raw));
 if (l  0) {
 if (errno == EAGAIN || errno == EINTR)
 break;
diff --git a/src/core/path.c b/src/core/path.c
index 656ed69..bc34f66 100644
--- a/src/core/path.c
+++ b/src/core/path.c
@@ -157,7 +157,7 @@ void path_spec_unwatch(PathSpec *s) {
 }
 
 int path_spec_fd_event(PathSpec *s, uint32_t revents) {
-uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct inotify_event);
+inotify_event_buffer_t buffer;
 struct inotify_event *e;
 ssize_t l;
 int r = 0;
@@ -167,7 +167,7 @@ int path_spec_fd_event(PathSpec *s, uint32_t revents) {
 return -EINVAL;
 }
 
-l = read(s-inotify_fd, buffer, sizeof(buffer));
+l = read(s-inotify_fd, buffer.raw, sizeof(buffer.raw));
 if (l  0) {
 if (errno == EAGAIN || errno == EINTR)
 return 0;
diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index d46dc3c..5f65116 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -2188,11 +2188,11 @@ _public_ int sd_journal_process(sd_journal *j) {
 j-last_process_usec = now(CLOCK_MONOTONIC);
 
 for (;;) {
-uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct 
inotify_event);
+inotify_event_buffer_t buffer;
 struct inotify_event *e;
 ssize_t l;
 
-l = read(j-inotify_fd, buffer, sizeof(buffer));
+l = read(j-inotify_fd, buffer.raw, sizeof(buffer.raw));
 if (l  0) {
 if (errno == EAGAIN || errno == EINTR)
 return got_something ? determine_change(j) : 
SD_JOURNAL_NOP;
diff --git a/src/shared/util.c b/src/shared/util.c
index 06b6077..2fbcdab 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -39,7 +39,6 @@
 #include linux/tiocl.h
 #include termios.h
 #include stdarg.h
-#include sys/inotify.h
 #include sys/poll.h
 #include ctype.h
 #include sys/prctl.h
@@ -2106,7 +2105,7 @@ int acquire_terminal(
 assert(notify = 0);
 
 for (;;) {
-uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct 
inotify_event);
+inotify_event_buffer_t buffer;
 struct inotify_event *e;
 ssize_t l;
 
@@ -2129,7 +2128,7 @@ int acquire_terminal(
 }
 }
 
-l = read(notify, buffer, sizeof(buffer));
+l = read(notify, buffer.raw, sizeof(buffer.raw));
 if (l  0) {
 if (errno == EINTR || errno == EAGAIN)
 continue;
diff --git a/src/shared/util.h b/src/shared/util.h
index 1804b8c..e9af32a 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -42,6 +42,7 @@
 #include locale.h
 #include mntent.h
 #include sys/socket.h
+#include sys/inotify.h
 
 #if SIZEOF_PID_T == 4
 #  define PID_FMT % PRIu32
@@ -1047,8 +1048,13 @@ int sethostname_idempotent(const char *s);
 #define INOTIFY_EVENT_MAX (sizeof(struct inotify_event) + NAME_MAX + 1)
 
 #define FOREACH_INOTIFY_EVENT(e, buffer, sz) \
-for ((e) = (struct inotify_event*) (buffer);\
- (uint8_t*) (e)  (uint8_t*) (buffer) + (sz); \
+for ((e) = (struct inotify_event*) (buffer.ev);\
+ (uint8_t*) (e)  (uint8_t*) (buffer.raw) + (sz); \
  (e) = (struct inotify_event*) ((uint8_t*) (e) + sizeof(struct 
inotify_event) + (e)-len))
 
+typedef union {
+struct inotify_event ev;
+uint8_t raw[INOTIFY_EVENT_MAX];
+} inotify_event_buffer_t;
+
 #define laccess(path, mode) faccessat(AT_FDCWD, (path), (mode), 
AT_SYMLINK_NOFOLLOW)
diff --git a/src/udev/udevd.c 

Re: [systemd-devel] [PATCH] util: fix strict aliasing violations in use of struct inotify_event v5

[Lennart Poettering]

On Tue, 23.12.14 13:47, Shawn Paul Landden (sh...@churchofgit.com) wrote:

 There is alot of cleanup that will have to happen to turn on
 -fstrict-aliasing, but I think our code should be correct to the
 rule.

Applied with some minor changes! (we try to use _t only for things
that actually feel like types, you'd pass around via call-by-value,
not call-by-ref...)

Thanks!

 ---
  src/core/mount.c |  4 ++--
  src/core/path.c  |  4 ++--
  src/journal/sd-journal.c |  4 ++--
  src/shared/util.c|  5 ++---
  src/shared/util.h| 10 --
  src/udev/udevd.c |  4 ++--
  6 files changed, 18 insertions(+), 13 deletions(-)
 
 diff --git a/src/core/mount.c b/src/core/mount.c
 index f8731bb..18ee2a0 100644
 --- a/src/core/mount.c
 +++ b/src/core/mount.c
 @@ -1701,11 +1701,11 @@ static int mount_dispatch_io(sd_event_source *source, 
 int fd, uint32_t revents,
   * internal behaviour of libmount here. */
  
  for (;;) {
 -uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct 
 inotify_event);
 +inotify_event_buffer_t buffer;
  struct inotify_event *e;
  ssize_t l;
  
 -l = read(fd, buffer, sizeof(buffer));
 +l = read(fd, buffer.raw, sizeof(buffer.raw));
  if (l  0) {
  if (errno == EAGAIN || errno == EINTR)
  break;
 diff --git a/src/core/path.c b/src/core/path.c
 index 656ed69..bc34f66 100644
 --- a/src/core/path.c
 +++ b/src/core/path.c
 @@ -157,7 +157,7 @@ void path_spec_unwatch(PathSpec *s) {
  }
  
  int path_spec_fd_event(PathSpec *s, uint32_t revents) {
 -uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct inotify_event);
 +inotify_event_buffer_t buffer;
  struct inotify_event *e;
  ssize_t l;
  int r = 0;
 @@ -167,7 +167,7 @@ int path_spec_fd_event(PathSpec *s, uint32_t revents) {
  return -EINVAL;
  }
  
 -l = read(s-inotify_fd, buffer, sizeof(buffer));
 +l = read(s-inotify_fd, buffer.raw, sizeof(buffer.raw));
  if (l  0) {
  if (errno == EAGAIN || errno == EINTR)
  return 0;
 diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
 index d46dc3c..5f65116 100644
 --- a/src/journal/sd-journal.c
 +++ b/src/journal/sd-journal.c
 @@ -2188,11 +2188,11 @@ _public_ int sd_journal_process(sd_journal *j) {
  j-last_process_usec = now(CLOCK_MONOTONIC);
  
  for (;;) {
 -uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct 
 inotify_event);
 +inotify_event_buffer_t buffer;
  struct inotify_event *e;
  ssize_t l;
  
 -l = read(j-inotify_fd, buffer, sizeof(buffer));
 +l = read(j-inotify_fd, buffer.raw, sizeof(buffer.raw));
  if (l  0) {
  if (errno == EAGAIN || errno == EINTR)
  return got_something ? determine_change(j) : 
 SD_JOURNAL_NOP;
 diff --git a/src/shared/util.c b/src/shared/util.c
 index 06b6077..2fbcdab 100644
 --- a/src/shared/util.c
 +++ b/src/shared/util.c
 @@ -39,7 +39,6 @@
  #include linux/tiocl.h
  #include termios.h
  #include stdarg.h
 -#include sys/inotify.h
  #include sys/poll.h
  #include ctype.h
  #include sys/prctl.h
 @@ -2106,7 +2105,7 @@ int acquire_terminal(
  assert(notify = 0);
  
  for (;;) {
 -uint8_t buffer[INOTIFY_EVENT_MAX] _alignas_(struct 
 inotify_event);
 +inotify_event_buffer_t buffer;
  struct inotify_event *e;
  ssize_t l;
  
 @@ -2129,7 +2128,7 @@ int acquire_terminal(
  }
  }
  
 -l = read(notify, buffer, sizeof(buffer));
 +l = read(notify, buffer.raw, sizeof(buffer.raw));
  if (l  0) {
  if (errno == EINTR || errno == EAGAIN)
  continue;
 diff --git a/src/shared/util.h b/src/shared/util.h
 index 1804b8c..e9af32a 100644
 --- a/src/shared/util.h
 +++ b/src/shared/util.h
 @@ -42,6 +42,7 @@
  #include locale.h
  #include mntent.h
  #include sys/socket.h
 +#include sys/inotify.h
  
  #if SIZEOF_PID_T == 4
  #  define PID_FMT % PRIu32
 @@ -1047,8 +1048,13 @@ int sethostname_idempotent(const char *s);
  #define INOTIFY_EVENT_MAX (sizeof(struct inotify_event) + NAME_MAX + 1)
  
  #define FOREACH_INOTIFY_EVENT(e, buffer, sz) \
 -for ((e) = (struct inotify_event*) (buffer);\
 - (uint8_t*) (e)  (uint8_t*) (buffer) + (sz); \
 +for ((e) = (struct inotify_event*) (buffer.ev);\
 + (uint8_t*) (e)  (uint8_t*)