Broken PQtrace CopyData display
I used PQtrace to trace a logical decoding session, and was confused to see
lines like this:
2025-08-29 22:09:57.633980 F 38 CopyData 'r\x00\x00\x00\x00\xffffff8e\x07\xffffff85x\x00\x00\x00\x00\xffffff8e\x07\xffffff85x\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\xffffffe0\xffffff84\xffffff89R\xffffffd7\xffffffb8\x00'
The data doesn't make sense and has the wrong length. A quick look shows that
the \xffffff85 parts are a signedness issue (on my compiler char is signed).
I instead expect to see output like this:
2025-08-29 22:39:17.041261 F 38 CopyData 'r\x00\x00\x00\x00\x8e\x07\x89\xf8\x00\x00\x00\x00\x8e\x07\x89\xf8\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\xe0\x84\xf21Dh\x00'
The diff below fixes this particular problem, though they say bugs are like
mushrooms, if you find one then there are probably others nearby, so a more
comprehensive fix may be warranted.
diff --git i/src/interfaces/libpq/fe-trace.c w/src/interfaces/libpq/fe-trace.c
index a45f0d85587..f487c111fc7 100644
--- i/src/interfaces/libpq/fe-trace.c
+++ w/src/interfaces/libpq/fe-trace.c
@@ -212,7 +212,7 @@ pqTraceOutputNchar(FILE *pfdebug, int len, const char *data, int *cursor, bool s
else
{
fwrite(v + next, 1, i - next, pfdebug);
- fprintf(pfdebug, "\\x%02x", v[i]);
+ fprintf(pfdebug, "\\x%02x", (unsigned char) v[i]);
next = i + 1;
}
}
On Fri, Aug 29, 2025 at 10:45:18PM +0300, Ran Benita wrote:
I used PQtrace to trace a logical decoding session, and was confused to see
lines like this:2025-08-29 22:09:57.633980 F 38 CopyData 'r\x00\x00\x00\x00\xffffff8e\x07\xffffff85x\x00\x00\x00\x00\xffffff8e\x07\xffffff85x\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\xffffffe0\xffffff84\xffffff89R\xffffffd7\xffffffb8\x00'
The data doesn't make sense and has the wrong length. A quick look shows that
the \xffffff85 parts are a signedness issue (on my compiler char is signed).@@ -212,7 +212,7 @@ pqTraceOutputNchar(FILE *pfdebug, int len, const char *data, int *cursor, bool s else { fwrite(v + next, 1, i - next, pfdebug); - fprintf(pfdebug, "\\x%02x", v[i]); + fprintf(pfdebug, "\\x%02x", (unsigned char) v[i]); next = i + 1; } }
Yeah. Not a lot of people use the libpq tracing, but it would be
better to show non-printable data in a consistent way.
The diff below fixes this particular problem, though they say bugs are like
mushrooms, if you find one then there are probably others nearby, so a more
comprehensive fix may be warranted.
There's one more mushroom: pqTraceOutputByte1() also uses a %02X
without a cast for non-printable data. Note as well
logicalmsg_desc(), auth-oauth.c, mbprint.c (which uses an unsigned
char type in input to force things).
--
Michael
On Sun, Aug 31, 2025 at 01:53:50PM +0900, Michael Paquier wrote:
Yeah. Not a lot of people use the libpq tracing, but it would be
better to show non-printable data in a consistent way.
Done this one with db9405493b48.
--
Michael
On 2025-Sep-03, Michael Paquier wrote:
On Sun, Aug 31, 2025 at 01:53:50PM +0900, Michael Paquier wrote:
Yeah. Not a lot of people use the libpq tracing, but it would be
better to show non-printable data in a consistent way.Done this one with db9405493b48.
Thanks!
--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"La persona que no quería pecar / estaba obligada a sentarse
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