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commit    1518b7d76aadcbdffa6214555b82b995e7404b38
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Mon Oct 13 16:44:20 2025 +0000
First released in: 16.11, 17.7, 18.1

    Fix issue with reading zero bytes in Gzip_read.
    
    pg_dump expects a read request of zero bytes to be a no-op; see for
    example ReadStr().  Gzip_read got this wrong and falsely supposed
    that the resulting gzret == 0 indicated an error.  We could complicate
    that error-checking logic some more, but it seems best to just fall
    out immediately when passed size == 0.
    
    This bug breaks the nominally-supported case of manually gzip'ing
    the toc.dat file within a directory-style dump, so back-patch to v16
    where this code came in.  (Prior branches already have a short-circuit
    for size == 0 before their only gzread call.)
    
    Author: Tom Lane <tgl@sss.pgh.pa.us>
    Reviewed-by: Chao Li <li.evan.chao@gmail.com>
    Discussion: https://postgr.es/m/3515357.1760128017@sss.pgh.pa.us
    Backpatch-through: 16


 src/bin/pg_dump/compress_gzip.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/bin/pg_dump/compress_gzip.c b/src/bin/pg_dump/compress_gzip.c
index f76dd42219b..f7f17fa3b22 100644
--- a/src/bin/pg_dump/compress_gzip.c
+++ b/src/bin/pg_dump/compress_gzip.c
@@ -257,6 +257,10 @@ Gzip_read(void *ptr, size_t size, CompressFileHandle *CFH)
 	gzFile		gzfp = (gzFile) CFH->private_data;
 	int			gzret;
 
+	/* Reading zero bytes must be a no-op */
+	if (size == 0)
+		return 0;
+
 	gzret = gzread(gzfp, ptr, size);
 
 	/*


[parent: b835759ec7e8]