8000 PGPRO-5646: remove compiler warning (gcc 11.2.0) by MarinaPolyakova · Pull Request #11 · postgrespro/ptrack · GitHub
[go: up one dir, main page]
Skip to content

PGPRO-5646: remove compiler warning (gcc 11.2.0) #11

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Oct 22, 2021
Merged

PGPRO-5646: remove compiler warning (gcc 11.2.0) #11

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
PGPRO-5646: remove compiler warning (gcc 11.2.0) 
In function ‘ptrack_write_chunk’,
    inlined from ‘ptrackCheckpoint’ at engine.c:397:2:
engine.c:78:13: warning: ‘write’ reading 8 bytes from a region of size 4
[-Wstringop-overread]
   78 |         if (write(fd, chunk, size) != size)
      |             ^~~~~~~~~~~~~~~~~~~~~~
In file included from engine.c:47:
engine.c: In function ‘ptrackCheckpoint’:
engine.h:55:25: note: source object ‘magic’ of size 4
   55 |         char            magic[PTRACK_MAGIC_SIZE];
      |                         ^~~~~
In file included from engine.c:22:
/usr/include/unistd.h:378:16: note: in a call to function ‘write’ declared with
attribute ‘access (read_only, 2, 3)’
  378 | extern ssize_t write (int __fd, const void *__buf, size_t __n) __wur
      |                ^~~~~

In C a pointer to the first field of a structure and a pointer to the structure
itself are always equal. Add a compile-time assertion check in case the field
magic is not the first field in the structure PtrackMapHdr in the future.

Thanks to Maksim Orlov for the review.
  • Loading branch information
Marina Polyakova committed Oct 20, 2021
commit 3dbc4fa6f70ea74c46dd0de80d35726efded93fa
12 changes: 11 additions & 1 deletion engine.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -394,7 +394,17 @@ ptrackCheckpoint(void)
*
* Write both magic and varsion_num at once.
*/
ptrack_write_chunk(ptrack_tmp_fd, &crc, (char *) &ptrack_map->magic,

/*
* Previously we read from the field magic, now we read from the beginning
* of the structure PtrackMapHdr. Make sure nothing has changed since then.
*/
StaticAssertStmt(
offsetof(PtrackMapHdr, magic) == 0,
"old write format for PtrackMapHdr.magic and PtrackMapHdr.version_num "
"is not upward-compatible");

ptrack_write_chunk(ptrack_tmp_fd, &crc, (char *) ptrack_map,
offsetof(PtrackMapHdr, init_lsn));

init_lsn = pg_atomic_read_u64(&ptrack_map->init_lsn);
Expand Down
0