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Commit033471d

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author
Marina Polyakova
committed
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 withattribute ‘access (read_only, 2, 3)’ 378 | extern ssize_t write (int __fd, const void *__buf, size_t __n) __wur | ^~~~~To avoid changing other code for the fields magic and version_num in thestructure PtrackMapHdr, use two calls to ptrack_write_chunk to write them to thefile. (This function is called a few times later, so why not add another call?)Add a compile-time assertion check that nothing has actually changed (e.g.alignment is fine).
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‎engine.c

Lines changed: 14 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -391,11 +391,22 @@ ptrackCheckpoint(void)
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* We are writing ptrack map values to file, but we want to simply map it
392392
* into the memory with mmap after a crash/restart. That way, we have to
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* write values taking into account all paddings/alignments.
394-
*
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* Write both magic and varsion_num at once.
396394
*/
395+
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/*
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* Earlier we wrote both magic and varsion_num at once. Make sure nothing
398+
* has changed since then (e.g. alignment is fine).
399+
*/
400+
StaticAssertStmt(
401+
sizeof(ptrack_map->magic)+sizeof(ptrack_map->version_num)==
402+
offsetof(PtrackMapHdr,init_lsn),
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"old write format for PtrackMapHdr.magic and PtrackMapHdr.version_num "
404+
"is not upward-compatible");
405+
397406
ptrack_write_chunk(ptrack_tmp_fd,&crc, (char*)&ptrack_map->magic,
398-
offsetof(PtrackMapHdr,init_lsn));
407+
sizeof(ptrack_map->magic));
408+
ptrack_write_chunk(ptrack_tmp_fd,&crc, (char*)&ptrack_map->version_num,
409+
sizeof(ptrack_map->version_num));
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400411
init_lsn=pg_atomic_read_u64(&ptrack_map->init_lsn);
401412

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