avoid an unwarranted "memory exhausted"

[Jim Meyering]

I was surprised to see a false report of "memory exhausted". This fixes it.
I've also tweaked configure.ac for warning-enabled builds on some systems:

>From 01103f62481f8b6d59dc1aba5c2460532bc75012 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering@fb.com>
Date: Sun, 20 Mar 2022 09:43:30 -0700
Subject: [PATCH 1/2] grep: very long lines no longer evoke unwarranted "memory
 exhausted"

When calling xpalloc (NULL, &n, incr_min, alloc_max, 1) with
nontrivial ALLOC_MAX, this must hold: N + INCR_MIN <= ALLOC_MAX.
With a very long line, it did not, and grep would mistakenly fail
with a report of "memory exhausted".
* src/grep.c (fillbuf): When using nontrivial ALLOC_MAX, ensure it
is at least N+INCR_MIN.
* tests/fillbuf-long-line: New file, to test for this.
* tests/Makefile.am (TESTS): Add its name.
---
 src/grep.c              |  2 +-
 tests/Makefile.am       |  1 +
 tests/fillbuf-long-line | 11 +++++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100755 tests/fillbuf-long-line

diff --git a/src/grep.c b/src/grep.c
index 9c933e4..4109ae4 100644
--- a/src/grep.c
+++ b/src/grep.c
@@ -984,7 +984,7 @@ fillbuf (idx_t save, struct stat const *st)
               ptrdiff_t a;
               if (0 <= to_be_read
                   && INT_ADD_OK (to_be_read, save + min_after_buflim, &a))
-                alloc_max = a;
+                alloc_max = MAX (a, bufalloc + incr_min);
             }

           newbuf = xpalloc (NULL, &bufalloc, incr_min, alloc_max, 1);
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 04a9eee..708980d 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -104,6 +104,7 @@ TESTS =                                             \
   fgrep-longest                                        \
   file                                         \
   filename-lineno.pl                           \
+  fillbuf-long-line                            \
   fmbtest                                      \
   foad1                                                \
   grep-dev-null                                        \
diff --git a/tests/fillbuf-long-line b/tests/fillbuf-long-line
new file mode 100755
index 0000000..5a8d339
--- /dev/null
+++ b/tests/fillbuf-long-line
@@ -0,0 +1,11 @@
+#!/bin/sh
+# This would fail for v3.7-15-ge3694e9 .. grep-v3.7-48-g5c3c427
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+
+printf %0104681d 0 > in || framework_failure_
+
+fail=0
+
+returns_ 1 grep xx in || fail=1
+
+Exit $fail
-- 
2.35.1.273.ge6ebfd0e8c


>From 08d68a84adeb7270485a971b9045a01a53603402 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering@fb.com>
Date: Sun, 20 Mar 2022 11:05:31 -0700
Subject: [PATCH 2/2] build: avoid build failure on systems that must compile
 regexec.c

With --enable-gcc-warnings, compiling regexec.h would fail due to
its use of a single variable-length array.
* configure.ac: Add -Wvla to the list of disabled warnings and
remove most of the others, that no longer need to be disabled.
---
 configure.ac | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/configure.ac b/configure.ac
index 98d757a..0a97982 100644
--- a/configure.ac
+++ b/configure.ac
@@ -128,18 +128,9 @@ if test $gl_gcc_warnings != no; then

   nw=$ew
   # This, $nw, is the list of warnings we disable.
-  nw="$nw -Wdeclaration-after-statement" # too useful to forbid
-  nw="$nw -Waggregate-return"       # anachronistic
-  nw="$nw -Wlong-long"              # C90 is anachronistic (lib/gethrxtime.h)
-  nw="$nw -Wc++-compat"             # We don't care about C++ compilers
-  nw="$nw -Wundef"                  # Warns on '#if GNULIB_FOO' etc in gnulib
+  nw="$nw -Wvla"                    # suppress a warning in regexec.h
   nw="$nw -Wsystem-headers"         # Don't let system headers trigger warnings
-  nw="$nw -Wpadded"                 # Our structs are not padded
-  nw="$nw -Wstack-protector"        # generates false alarms for useful code
-  nw="$nw -Wswitch-default"         # Too many warnings for now
-  nw="$nw -Wunsafe-loop-optimizations" # OK to suppress unsafe optimizations
-  nw="$nw -Winline"                 # streq.h's streq4, streq6 and strcaseeq6
-  nw="$nw -Wstrict-overflow"        # regexec.c
+

   gl_MANYWARN_ALL_GCC([ws])
   gl_MANYWARN_COMPLEMENT([ws], [$ws], [$nw])
-- 
2.35.1.273.ge6ebfd0e8c