bug#48680: "zgrep -q" failing with some large files

[Paul Eggert]

What platform are you running on? Who built zgrep and gzip on your 
platform? In what directories are the zgrep and gzip executables? What 
is the output of "gzip --version"?

What is the output of the following shell command?

  unset BASH_ENV; bash -x ./zgrep -q fox synthetic.log.bz2

Here's the output I get for that last command, for comparison. I am 
running gzip 1.10 (which I compiled) on Fedora 33 x86-64. This system's 
bash is version 5.0.17.

+ grep='${GREP-'\''/usr/bin/grep'\''}'
+ version='zgrep (gzip) 1.10
Copyright (C) 2010-2018 Free Software Foundation, Inc.
This is free software.  You may redistribute copies of it under the terms of
the GNU General Public License <https://www.gnu.org/licenses/gpl.html>.
There is NO WARRANTY, to the extent permitted by law.

Written by Jean-loup Gailly.'
+ usage='Usage: ./zgrep [OPTION]... [-e] PATTERN [FILE]...
Look for instances of PATTERN in the input FILEs, using their
uncompressed contents if they are compressed.

OPTIONs are the same as for '\''grep'\'', except that the following 
'\''grep'\''
options are not supported: --dereference-recursive (-R), --directories (-d),
--exclude, --exclude-from, --exclude-dir, --include, --null (-Z),
--null-data (-z), and --recursive (-r).

Report bugs to <bug-gzip@gnu.org>.'
+ escape='
  s/'\''/'\''\\'\'''\''/g
  $s/$/'\''/
'
+ operands=
+ have_pat=0
+ files_with_matches=0
+ files_without_matches=0
+ no_filename=0
+ with_filename=0
+ pattmp=
+ test 3 -ne 0
+ option=-q
+ shift
+ optarg=
+ case $option in
+ case $option in
+ case $option in
+ option=''\''-q'\'''
+ grep='${GREP-'\''/usr/bin/grep'\''} '\''-q'\'''
+ test 2 -ne 0
+ option=fox
+ shift
+ optarg=
+ case $option in
+ case $option in
+ operands=' '\''fox'\'''
+ continue
+ test 1 -ne 0
+ option=synthetic.log.bz2
+ shift
+ optarg=
+ case $option in
+ case $option in
+ operands=' '\''fox'\'' '\''synthetic.log.bz2'\'''
+ continue
+ test 0 -ne 0
+ eval 'set --  '\''fox'\'' '\''synthetic.log.bz2'\'' ${1+"$@"}'
++ set -- fox synthetic.log.bz2
+ test 0 -eq 0
+ case ${1?"missing pattern; try \`$0 --help' for help"} in
+ grep='${GREP-'\''/usr/bin/grep'\''} '\''-q'\'' -- '\''fox'\'''
+ shift
+ test 1 -eq 0
+ exec
+ res=1
+ for i in "$@"
++ exec
++ gzip -cdfq -- synthetic.log.bz2
++ test 0 -eq 1
++ test 0 -eq 1
++ test 0 -eq 0
++ test 1 -eq 1
++ eval '${GREP-'\''/usr/bin/grep'\''} '\''-q'\'' -- '\''fox'\'''
+++ /usr/bin/grep -q -- fox
++ echo 0
+ gzip_status=0
+ r=1
+ test 0 -eq 2
+ test 0 -eq 1
+ test 1 -lt 0
+ test 1 -le 1
+ test 1 -le 1
+ test 1 -lt 1
+ test 126 -le 1
+ test -n ''
+ test 128 -le 1
+ exit 1