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Fix incorrect data type choices in some read and write calls.

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Recently-introduced code in reconstruct.c was using "unsigned"
to store the result of read(), pg_pread(), or write().  This is
completely bogus: it breaks subsequent tests for the result being
negative, as we're being reminded of by a chorus of buildfarm
warnings.  Switch to "int" as was doubtless intended.  (There are
several other uses of "unsigned" in this file that also look poorly
chosen to me, but for now I'm just trying to clean up the buildfarm.)

A larger problem is that "int" is not necessarily wide enough to hold
the result: per POSIX, all these functions return ssize_t.  In places
where the requested read or write length clearly fits in int, that's
academic.  It may be academic anyway as long as we constrain
individual data files to 1GB, since even a readv or writev-like
operation would then not be responsible for transferring more than
1GB.  Nonetheless it seems like trouble waiting to happen, so I made
a pass over readv and writev calls and fixed the result variables
where that seemed appropriate.  We might want to think about changing
some of the fd.c functions to return ssize_t too, for future-proofing;
but I didn't tackle that here.

Discussion: https://postgr.es/m/1672202.1703441340@sss.pgh.pa.us
This commit is contained in:
Tom Lane 2023-12-27 11:02:53 -05:00
parent da083b20f6
commit 98c6231d19
3 changed files with 15 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/backend/access/transam/xlog.c
View File

@ -2280,7 +2280,7 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible)
char *from;
Size nbytes;
Size nleft;
int written;
ssize_t written;
instr_time start;
/* OK to write the page(s) */

12
src/backend/backup/basebackup.c
View File

@ -117,8 +117,8 @@ static void perform_base_backup(basebackup_options *opt, bbsink *sink,
IncrementalBackupInfo *ib);
static void parse_basebackup_options(List *options, basebackup_options *opt);
static int compareWalFileNames(const ListCell *a, const ListCell *b);
static int basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
const char *filename, bool partial_read_ok);
static ssize_t basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
const char *filename, bool partial_read_ok);
/* Was the backup currently in-progress initiated in recovery mode? */
static bool backup_started_in_recovery = false;
@ -525,7 +525,7 @@ perform_base_backup(basebackup_options *opt, bbsink *sink,
{
char *walFileName = (char *) lfirst(lc);
int fd;
size_t cnt;
ssize_t cnt;
pgoff_t len = 0;
snprintf(pathbuf, MAXPGPATH, XLOGDIR "/%s", walFileName);
@ -2079,11 +2079,11 @@ convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
*
* Returns the number of bytes read.
*/
static int
static ssize_t
basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
const char *filename, bool partial_read_ok)
{
int rc;
ssize_t rc;
pgstat_report_wait_start(WAIT_EVENT_BASEBACKUP_READ);
rc = pg_pread(fd, buf, nbytes, offset);
@ -2096,7 +2096,7 @@ basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
if (!partial_read_ok && rc > 0 && rc != nbytes)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": read %d of %zu",
errmsg("could not read file \"%s\": read %zd of %zu",
filename, rc, nbytes)));
return rc;

16
src/bin/pg_combinebackup/reconstruct.c
View File

@ -504,7 +504,7 @@ make_rfile(char *filename, bool missing_ok)
static void
read_bytes(rfile *rf, void *buffer, unsigned length)
{
unsigned rb = read(rf->fd, buffer, length);
int rb = read(rf->fd, buffer, length);
if (rb != length)
{
@ -512,7 +512,7 @@ read_bytes(rfile *rf, void *buffer, unsigned length)
pg_fatal("could not read file \"%s\": %m", rf->filename);
else
pg_fatal("could not read file \"%s\": read only %d of %d bytes",
rf->filename, (int) rb, length);
rf->filename, rb, length);
}
}
@ -614,7 +614,7 @@ write_reconstructed_file(char *input_filename,
{
uint8 buffer[BLCKSZ];
rfile *s = sourcemap[i];
unsigned wb;
int wb;
/* Update accounting information. */
if (s == NULL)
@ -641,7 +641,7 @@ write_reconstructed_file(char *input_filename,
}
else
{
unsigned rb;
int rb;
/* Read the block from the correct source, except if dry-run. */
rb = pg_pread(s->fd, buffer, BLCKSZ, offsetmap[i]);
@ -650,9 +650,9 @@ write_reconstructed_file(char *input_filename,
if (rb < 0)
pg_fatal("could not read file \"%s\": %m", s->filename);
else
pg_fatal("could not read file \"%s\": read only %d of %d bytes at offset %u",
s->filename, (int) rb, BLCKSZ,
(unsigned) offsetmap[i]);
pg_fatal("could not read file \"%s\": read only %d of %d bytes at offset %llu",
s->filename, rb, BLCKSZ,
(unsigned long long) offsetmap[i]);
}
}
@ -663,7 +663,7 @@ write_reconstructed_file(char *input_filename,
pg_fatal("could not write file \"%s\": %m", output_filename);
else
pg_fatal("could not write file \"%s\": wrote only %d of %d bytes",
output_filename, (int) wb, BLCKSZ);
output_filename, wb, BLCKSZ);
}
/* Update the checksum computation. */