2 patches: build with warnings enabled and latest gcc

[Jim Meyering]

I tried to build coreutils with warnings enabled and using the latest
gcc (built from head of gcc.git) and was irritated to see it fail with
a few of the new warnings evoking apparent false positives, like these:

  lib/human.c: In function 'human_readable':
  lib/human.c:232:24: error: '%.0Lf' directive output between 1 and 4934 \
    bytes may exceed minimum required size of 4095 [-Werror=format-overflow=]
       sprintf (buf, "%.0Lf", adjust_value (inexact_style, damt));

  parse-datetime.y:1626:33: error: ' TZ=' directive output truncated writing \
   4 bytes into a region of size 1 [-Werror=format-truncation=]
  parse-datetime.y:1626:33: note: assuming directive output of 1 byte
  In file included from /usr/include/stdio.h:939:0,
                   from ./lib/stdio.h:43,
                   from parse-datetime.y:68:
  /usr/include/bits/stdio2.h:64:10: note: '__builtin___snprintf_chk' output 5 \
     or more bytes (assuming 6) into a destination of size 1
     return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          __bos (__s), __fmt, __va_arg_pack ());
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hoping they'd been addressed in latest gnulib, I tried updating the submodule,
but with that, even bootstrap failed due to inability to apply coreutils'
gl/modules/tempname.diff patch.

I adjusted that .diff file and upgraded gnulib to latest in the first patch
below, but the warning/error issues persisted, so I disabled the offenders
via the second patch.  Now, "make distcheck" nearly completes.

I'll push these soon if no one objects.

>From 0b7fababf893803505e0382f71dc755951c98cc8 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Fri, 11 Aug 2017 17:33:15 -0700
Subject: [PATCH 1/2] gnulib: update to latest and adjust
 gl/modules/tempname.diff

* gnulib: Update to latest.
* gl/modules/tempname.diff: This patch failed to apply.
Adjust it to reflect removal of the secure_getenv dependency.
---
 gl/modules/tempname.diff | 3 +--
 gnulib                   | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/gl/modules/tempname.diff b/gl/modules/tempname.diff
index 4aee47c6f..d572734b6 100644
--- a/gl/modules/tempname.diff
+++ b/gl/modules/tempname.diff
@@ -2,12 +2,11 @@ diff --git a/modules/tempname b/modules/tempname
 index 570ea54..f1be8ff 100644
 --- a/modules/tempname
 +++ b/modules/tempname
-@@ -12,7 +12,9 @@ extensions
+@@ -12,6 +12,8 @@
  fcntl-h
  gettimeofday
  lstat
 +randint
- secure_getenv
 +stdbool
  stdint
  sys_stat
diff --git a/gnulib b/gnulib
index ac2fdcad6..0474f8e6a 160000
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit ac2fdcad666d24d51a32a152fe1b3911b610344d
+Subproject commit 0474f8e6a85621c276dfc47099b9863a47f96a0d
--
2.14.1.145.gb3622a4ee


>From 96101eef33b2a56bd169560cd806b4b3237d2430 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Sat, 12 Aug 2017 13:51:19 -0700
Subject: [PATCH 2/2] build: adjust warning options to work with latest GCC

* configure.ac: Disable some new warnings to avoid false positives.
Building with warnings enabled and latest gcc would evoke build
failure without these changes.  Disable the following in coreutils
proper: -Wformat-overflow=2 -Wformat-truncation=2, and
disable these for gnulib: -Wformat-truncation=2 -Wduplicated-branches
---
 configure.ac | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/configure.ac b/configure.ac
index 7c7c8c238..73e445d02 100644
--- a/configure.ac
+++ b/configure.ac
@@ -133,6 +133,8 @@ if test "$gl_gcc_warnings" = yes; then
   nw="$nw -Wswitch-default"         # Too many warnings for now
   nw="$nw -Wstack-protector"        # not worth working around
   nw="$nw -Wtype-limits"            # False alarms for portable code
+  nw="$nw -Wformat-overflow=2"      # False alarms due to GCC bug 80776
+  nw="$nw -Wformat-truncation=2"    # False alarm in ls.c, probably related
   # things I might fix soon:
   nw="$nw -Wfloat-equal"            # sort.c, seq.c
   nw="$nw -Wmissing-format-attribute" # copy.c
@@ -193,6 +195,8 @@ if test "$gl_gcc_warnings" = yes; then
   # We use a slightly smaller set of warning options for lib/.
   # Remove the following and save the result in GNULIB_WARN_CFLAGS.
   nw=
+  nw="$nw -Wduplicated-branches"    # Too many false alarms
+  nw="$nw -Wformat-truncation=2"
   nw="$nw -Wstrict-overflow"
   nw="$nw -Wuninitialized"
   nw="$nw -Wunused-macros"
--
2.14.1.145.gb3622a4ee