Fix public issue #6: Add a --with-gflags for disabling gflags autodetection

and using a manually given setting (use/don't use) instead.

R=csilvers
DELTA=16  (13 added, 0 deleted, 3 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=991


git-svn-id: http://snappy.googlecode.com/svn/trunk@9 03e5f5b5-db94-4691-08a0-1a8bf15f6143

6 files changed, 255 insertions, 172 deletions

diff --git a/autom4te.cache/output.0 b/autom4te.cache/output.0
index 61a6529..f18bb03 100644
--- a/autom4te.cache/output.0
+++ b/autom4te.cache/output.0
@@ -884,6 +884,7 @@ enable_dependency_tracking
 with_gnu_ld
 enable_libtool_lock
 enable_gtest
+with_gflags
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1542,6 +1543,8 @@ Optional Packages:
   --with-pic              try to use only PIC/non-PIC objects @<:@default=use
                           both@:>@
   --with-gnu-ld           assume the C compiler uses GNU ld @<:@default=no@:>@
+  --with-gflags           use Google Flags package to enhance the unit test
+                          @<:@default=check@:>@
 
 Some influential environment variables:
   CC          C compiler command
@@ -14828,6 +14831,17 @@ fi
 
 
 
+@%:@ Check whether --with-gflags was given.
+if test "${with_gflags+set}" = set; then :
+  withval=$with_gflags; 
+else
+  with_gflags=check
+fi
+
+
+if test "x$with_gflags" != "xno"; then
+  
+
 if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
 	if test -n "$ac_tool_prefix"; then
   # Extract the first word of "${ac_tool_prefix}pkg-config", so it can be a program name with args.
@@ -15003,11 +15017,19 @@ fi
 
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
-                true # Ignore; we can live without it.
-
+                if test "x$with_gflags" != "xcheck"; then
+      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "--with-gflags was given, but test for gflags failed
+See \`config.log' for more details." "$LINENO" 5; }
+    fi
 elif test $pkg_failed = untried; then
-	true # Ignore; we can live without it.
-
+	if test "x$with_gflags" != "xcheck"; then
+      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "--with-gflags was given, but test for gflags failed
+See \`config.log' for more details." "$LINENO" 5; }
+    fi
 else
 	gflags_CFLAGS=$pkg_cv_gflags_CFLAGS
 	gflags_LIBS=$pkg_cv_gflags_LIBS
@@ -15017,6 +15039,7 @@ $as_echo "yes" >&6; }
 $as_echo "@%:@define HAVE_GFLAGS 1" >>confdefs.h
 
 fi
+fi
 
 # See if we have __builtin_expect.
 # TODO: Use AC_CACHE.
diff --git a/autom4te.cache/output.1 b/autom4te.cache/output.1
index 3e4a418..ecf6e88 100644
--- a/autom4te.cache/output.1
+++ b/autom4te.cache/output.1
@@ -884,6 +884,7 @@ enable_dependency_tracking
 with_gnu_ld
 enable_libtool_lock
 enable_gtest
+with_gflags
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1542,6 +1543,8 @@ Optional Packages:
   --with-pic              try to use only PIC/non-PIC objects @<:@default=use
                           both@:>@
   --with-gnu-ld           assume the C compiler uses GNU ld @<:@default=no@:>@
+  --with-gflags           use Google Flags package to enhance the unit test
+                          @<:@default=check@:>@
 
 Some influential environment variables:
   CC          C compiler command
@@ -14824,6 +14827,17 @@ fi
 
 
 
+@%:@ Check whether --with-gflags was given.
+if test "${with_gflags+set}" = set; then :
+  withval=$with_gflags; 
+else
+  with_gflags=check
+fi
+
+
+if test "x$with_gflags" != "xno"; then
+  
+
 if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
 	if test -n "$ac_tool_prefix"; then
   # Extract the first word of "${ac_tool_prefix}pkg-config", so it can be a program name with args.
@@ -14999,11 +15013,19 @@ fi
 
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
-                true # Ignore; we can live without it.
-
+                if test "x$with_gflags" != "xcheck"; then
+      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "--with-gflags was given, but test for gflags failed
+See \`config.log' for more details." "$LINENO" 5; }
+    fi
 elif test $pkg_failed = untried; then
-	true # Ignore; we can live without it.
-
+	if test "x$with_gflags" != "xcheck"; then
+      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "--with-gflags was given, but test for gflags failed
+See \`config.log' for more details." "$LINENO" 5; }
+    fi
 else
 	gflags_CFLAGS=$pkg_cv_gflags_CFLAGS
 	gflags_LIBS=$pkg_cv_gflags_LIBS
@@ -15013,6 +15035,7 @@ $as_echo "yes" >&6; }
 $as_echo "@%:@define HAVE_GFLAGS 1" >>confdefs.h
 
 fi
+fi
 
 # See if we have __builtin_expect.
 # TODO: Use AC_CACHE.
diff --git a/autom4te.cache/traces.0 b/autom4te.cache/traces.0
index a1d9030..b506c40 100644
--- a/autom4te.cache/traces.0
+++ b/autom4te.cache/traces.0
@@ -2515,47 +2515,48 @@ m4trace:configure.ac:23: -1- m4_pattern_allow([^HAVE_GTEST_TRUE$])
 m4trace:configure.ac:23: -1- m4_pattern_allow([^HAVE_GTEST_FALSE$])
 m4trace:configure.ac:23: -1- _AM_SUBST_NOTMAKE([HAVE_GTEST_TRUE])
 m4trace:configure.ac:23: -1- _AM_SUBST_NOTMAKE([HAVE_GTEST_FALSE])
-m4trace:configure.ac:24: -1- PKG_CHECK_MODULES([gflags], [libgflags], [AC_DEFINE([HAVE_GFLAGS], [1], [Use the gflags package for command-line parsing.])], [true # Ignore; we can live without it.
-])
-m4trace:configure.ac:24: -1- PKG_PROG_PKG_CONFIG
-m4trace:configure.ac:24: -1- m4_pattern_forbid([^_?PKG_[A-Z_]+$])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^PKG_CONFIG(_PATH)?$])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^PKG_CONFIG$])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^PKG_CONFIG$])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^gflags_CFLAGS$])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^gflags_LIBS$])
-m4trace:configure.ac:24: -1- PKG_CHECK_EXISTS([libgflags], [pkg_cv_[]gflags_CFLAGS=`$PKG_CONFIG --[]cflags "libgflags" 2>/dev/null`], [pkg_failed=yes])
-m4trace:configure.ac:24: -1- PKG_CHECK_EXISTS([libgflags], [pkg_cv_[]gflags_LIBS=`$PKG_CONFIG --[]libs "libgflags" 2>/dev/null`], [pkg_failed=yes])
-m4trace:configure.ac:24: -1- _PKG_SHORT_ERRORS_SUPPORTED
-m4trace:configure.ac:24: -1- m4_pattern_allow([^HAVE_GFLAGS$])
-m4trace:configure.ac:33: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
+m4trace:configure.ac:33: -1- PKG_CHECK_MODULES([gflags], [libgflags], [AC_DEFINE([HAVE_GFLAGS], [1], [Use the gflags package for command-line parsing.])], [if test "x$with_gflags" != "xcheck"; then
+      AC_MSG_FAILURE([--with-gflags was given, but test for gflags failed])
+    fi])
+m4trace:configure.ac:33: -1- PKG_PROG_PKG_CONFIG
+m4trace:configure.ac:33: -1- m4_pattern_forbid([^_?PKG_[A-Z_]+$])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^PKG_CONFIG(_PATH)?$])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^PKG_CONFIG$])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^PKG_CONFIG$])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^gflags_CFLAGS$])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^gflags_LIBS$])
+m4trace:configure.ac:33: -1- PKG_CHECK_EXISTS([libgflags], [pkg_cv_[]gflags_CFLAGS=`$PKG_CONFIG --[]cflags "libgflags" 2>/dev/null`], [pkg_failed=yes])
+m4trace:configure.ac:33: -1- PKG_CHECK_EXISTS([libgflags], [pkg_cv_[]gflags_LIBS=`$PKG_CONFIG --[]libs "libgflags" 2>/dev/null`], [pkg_failed=yes])
+m4trace:configure.ac:33: -1- _PKG_SHORT_ERRORS_SUPPORTED
+m4trace:configure.ac:33: -1- m4_pattern_allow([^HAVE_GFLAGS$])
+m4trace:configure.ac:46: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
 You should run autoupdate.], [../../lib/autoconf/general.m4:2581: AC_TRY_COMPILE is expanded from...
-configure.ac:33: the top level])
-m4trace:configure.ac:43: -1- m4_pattern_allow([^HAVE_BUILTIN_EXPECT$])
-m4trace:configure.ac:50: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
+configure.ac:46: the top level])
+m4trace:configure.ac:56: -1- m4_pattern_allow([^HAVE_BUILTIN_EXPECT$])
+m4trace:configure.ac:63: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
 You should run autoupdate.], [../../lib/autoconf/general.m4:2581: AC_TRY_COMPILE is expanded from...
-configure.ac:50: the top level])
-m4trace:configure.ac:60: -1- m4_pattern_allow([^HAVE_BUILTIN_CTZ$])
-m4trace:configure.ac:65: -1- m4_pattern_allow([^HAVE_LIBZ$])
-m4trace:configure.ac:66: -1- m4_pattern_allow([^HAVE_LIBLZO2$])
-m4trace:configure.ac:67: -1- m4_pattern_allow([^HAVE_LIBLZF$])
-m4trace:configure.ac:68: -1- m4_pattern_allow([^HAVE_LIBFASTLZ$])
-m4trace:configure.ac:69: -1- m4_pattern_allow([^HAVE_LIBQUICKLZ$])
-m4trace:configure.ac:73: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
-m4trace:configure.ac:75: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
-m4trace:configure.ac:78: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
-m4trace:configure.ac:80: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
-m4trace:configure.ac:88: -1- m4_pattern_allow([^SNAPPY_MAJOR$])
-m4trace:configure.ac:89: -1- m4_pattern_allow([^SNAPPY_MINOR$])
-m4trace:configure.ac:90: -1- m4_pattern_allow([^SNAPPY_PATCHLEVEL$])
-m4trace:configure.ac:91: -1- m4_pattern_allow([^SNAPPY_LTVERSION$])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^LIB@&t@OBJS$])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^LTLIBOBJS$])
-m4trace:configure.ac:95: -1- AM_CONDITIONAL([am__EXEEXT], [test -n "$EXEEXT"])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^am__EXEEXT_TRUE$])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^am__EXEEXT_FALSE$])
-m4trace:configure.ac:95: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_TRUE])
-m4trace:configure.ac:95: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_FALSE])
-m4trace:configure.ac:95: -1- _AC_AM_CONFIG_HEADER_HOOK(["$ac_file"])
-m4trace:configure.ac:95: -1- _AM_OUTPUT_DEPENDENCY_COMMANDS
-m4trace:configure.ac:95: -1- _LT_PROG_LTMAIN
+configure.ac:63: the top level])
+m4trace:configure.ac:73: -1- m4_pattern_allow([^HAVE_BUILTIN_CTZ$])
+m4trace:configure.ac:78: -1- m4_pattern_allow([^HAVE_LIBZ$])
+m4trace:configure.ac:79: -1- m4_pattern_allow([^HAVE_LIBLZO2$])
+m4trace:configure.ac:80: -1- m4_pattern_allow([^HAVE_LIBLZF$])
+m4trace:configure.ac:81: -1- m4_pattern_allow([^HAVE_LIBFASTLZ$])
+m4trace:configure.ac:82: -1- m4_pattern_allow([^HAVE_LIBQUICKLZ$])
+m4trace:configure.ac:86: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
+m4trace:configure.ac:88: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
+m4trace:configure.ac:91: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
+m4trace:configure.ac:93: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
+m4trace:configure.ac:101: -1- m4_pattern_allow([^SNAPPY_MAJOR$])
+m4trace:configure.ac:102: -1- m4_pattern_allow([^SNAPPY_MINOR$])
+m4trace:configure.ac:103: -1- m4_pattern_allow([^SNAPPY_PATCHLEVEL$])
+m4trace:configure.ac:104: -1- m4_pattern_allow([^SNAPPY_LTVERSION$])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^LIB@&t@OBJS$])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^LTLIBOBJS$])
+m4trace:configure.ac:108: -1- AM_CONDITIONAL([am__EXEEXT], [test -n "$EXEEXT"])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^am__EXEEXT_TRUE$])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^am__EXEEXT_FALSE$])
+m4trace:configure.ac:108: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_TRUE])
+m4trace:configure.ac:108: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_FALSE])
+m4trace:configure.ac:108: -1- _AC_AM_CONFIG_HEADER_HOOK(["$ac_file"])
+m4trace:configure.ac:108: -1- _AM_OUTPUT_DEPENDENCY_COMMANDS
+m4trace:configure.ac:108: -1- _LT_PROG_LTMAIN
diff --git a/autom4te.cache/traces.1 b/autom4te.cache/traces.1
index f679ca0..0f31e2f 100644
--- a/autom4te.cache/traces.1
+++ b/autom4te.cache/traces.1
@@ -587,108 +587,108 @@ m4trace:configure.ac:23: -1- AC_SUBST_TRACE([HAVE_GTEST_FALSE])
 m4trace:configure.ac:23: -1- m4_pattern_allow([^HAVE_GTEST_FALSE$])
 m4trace:configure.ac:23: -1- _AM_SUBST_NOTMAKE([HAVE_GTEST_TRUE])
 m4trace:configure.ac:23: -1- _AM_SUBST_NOTMAKE([HAVE_GTEST_FALSE])
-m4trace:configure.ac:24: -1- m4_pattern_forbid([^_?PKG_[A-Z_]+$])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^PKG_CONFIG(_PATH)?$])
-m4trace:configure.ac:24: -1- AC_SUBST([PKG_CONFIG])
-m4trace:configure.ac:24: -1- AC_SUBST_TRACE([PKG_CONFIG])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^PKG_CONFIG$])
-m4trace:configure.ac:24: -1- AC_SUBST([PKG_CONFIG])
-m4trace:configure.ac:24: -1- AC_SUBST_TRACE([PKG_CONFIG])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^PKG_CONFIG$])
-m4trace:configure.ac:24: -1- AC_SUBST([gflags_CFLAGS])
-m4trace:configure.ac:24: -1- AC_SUBST_TRACE([gflags_CFLAGS])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^gflags_CFLAGS$])
-m4trace:configure.ac:24: -1- AC_SUBST([gflags_LIBS])
-m4trace:configure.ac:24: -1- AC_SUBST_TRACE([gflags_LIBS])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^gflags_LIBS$])
-m4trace:configure.ac:24: -1- AC_DEFINE_TRACE_LITERAL([HAVE_GFLAGS])
-m4trace:configure.ac:24: -1- m4_pattern_allow([^HAVE_GFLAGS$])
-m4trace:configure.ac:24: -1- AH_OUTPUT([HAVE_GFLAGS], [/* Use the gflags package for command-line parsing. */
+m4trace:configure.ac:33: -1- m4_pattern_forbid([^_?PKG_[A-Z_]+$])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^PKG_CONFIG(_PATH)?$])
+m4trace:configure.ac:33: -1- AC_SUBST([PKG_CONFIG])
+m4trace:configure.ac:33: -1- AC_SUBST_TRACE([PKG_CONFIG])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^PKG_CONFIG$])
+m4trace:configure.ac:33: -1- AC_SUBST([PKG_CONFIG])
+m4trace:configure.ac:33: -1- AC_SUBST_TRACE([PKG_CONFIG])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^PKG_CONFIG$])
+m4trace:configure.ac:33: -1- AC_SUBST([gflags_CFLAGS])
+m4trace:configure.ac:33: -1- AC_SUBST_TRACE([gflags_CFLAGS])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^gflags_CFLAGS$])
+m4trace:configure.ac:33: -1- AC_SUBST([gflags_LIBS])
+m4trace:configure.ac:33: -1- AC_SUBST_TRACE([gflags_LIBS])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^gflags_LIBS$])
+m4trace:configure.ac:33: -1- AC_DEFINE_TRACE_LITERAL([HAVE_GFLAGS])
+m4trace:configure.ac:33: -1- m4_pattern_allow([^HAVE_GFLAGS$])
+m4trace:configure.ac:33: -1- AH_OUTPUT([HAVE_GFLAGS], [/* Use the gflags package for command-line parsing. */
 @%:@undef HAVE_GFLAGS])
-m4trace:configure.ac:33: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
+m4trace:configure.ac:46: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
 You should run autoupdate.], [../../lib/autoconf/general.m4:2581: AC_TRY_COMPILE is expanded from...
-configure.ac:33: the top level])
-m4trace:configure.ac:43: -1- AC_DEFINE_TRACE_LITERAL([HAVE_BUILTIN_EXPECT])
-m4trace:configure.ac:43: -1- m4_pattern_allow([^HAVE_BUILTIN_EXPECT$])
-m4trace:configure.ac:43: -1- AH_OUTPUT([HAVE_BUILTIN_EXPECT], [/* Define to 1 if the compiler supports __builtin_expect. */
+configure.ac:46: the top level])
+m4trace:configure.ac:56: -1- AC_DEFINE_TRACE_LITERAL([HAVE_BUILTIN_EXPECT])
+m4trace:configure.ac:56: -1- m4_pattern_allow([^HAVE_BUILTIN_EXPECT$])
+m4trace:configure.ac:56: -1- AH_OUTPUT([HAVE_BUILTIN_EXPECT], [/* Define to 1 if the compiler supports __builtin_expect. */
 @%:@undef HAVE_BUILTIN_EXPECT])
-m4trace:configure.ac:50: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
+m4trace:configure.ac:63: -1- _m4_warn([obsolete], [The macro `AC_TRY_COMPILE' is obsolete.
 You should run autoupdate.], [../../lib/autoconf/general.m4:2581: AC_TRY_COMPILE is expanded from...
-configure.ac:50: the top level])
-m4trace:configure.ac:60: -1- AC_DEFINE_TRACE_LITERAL([HAVE_BUILTIN_CTZ])
-m4trace:configure.ac:60: -1- m4_pattern_allow([^HAVE_BUILTIN_CTZ$])
-m4trace:configure.ac:60: -1- AH_OUTPUT([HAVE_BUILTIN_CTZ], [/* Define to 1 if the compiler supports __builtin_ctz and friends. */
+configure.ac:63: the top level])
+m4trace:configure.ac:73: -1- AC_DEFINE_TRACE_LITERAL([HAVE_BUILTIN_CTZ])
+m4trace:configure.ac:73: -1- m4_pattern_allow([^HAVE_BUILTIN_CTZ$])
+m4trace:configure.ac:73: -1- AH_OUTPUT([HAVE_BUILTIN_CTZ], [/* Define to 1 if the compiler supports __builtin_ctz and friends. */
 @%:@undef HAVE_BUILTIN_CTZ])
-m4trace:configure.ac:65: -1- AH_OUTPUT([HAVE_LIBZ], [/* Define to 1 if you have the `z\' library (-lz). */
+m4trace:configure.ac:78: -1- AH_OUTPUT([HAVE_LIBZ], [/* Define to 1 if you have the `z\' library (-lz). */
 @%:@undef HAVE_LIBZ])
-m4trace:configure.ac:65: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBZ])
-m4trace:configure.ac:65: -1- m4_pattern_allow([^HAVE_LIBZ$])
-m4trace:configure.ac:66: -1- AH_OUTPUT([HAVE_LIBLZO2], [/* Define to 1 if you have the `lzo2\' library (-llzo2). */
+m4trace:configure.ac:78: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBZ])
+m4trace:configure.ac:78: -1- m4_pattern_allow([^HAVE_LIBZ$])
+m4trace:configure.ac:79: -1- AH_OUTPUT([HAVE_LIBLZO2], [/* Define to 1 if you have the `lzo2\' library (-llzo2). */
 @%:@undef HAVE_LIBLZO2])
-m4trace:configure.ac:66: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBLZO2])
-m4trace:configure.ac:66: -1- m4_pattern_allow([^HAVE_LIBLZO2$])
-m4trace:configure.ac:67: -1- AH_OUTPUT([HAVE_LIBLZF], [/* Define to 1 if you have the `lzf\' library (-llzf). */
+m4trace:configure.ac:79: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBLZO2])
+m4trace:configure.ac:79: -1- m4_pattern_allow([^HAVE_LIBLZO2$])
+m4trace:configure.ac:80: -1- AH_OUTPUT([HAVE_LIBLZF], [/* Define to 1 if you have the `lzf\' library (-llzf). */
 @%:@undef HAVE_LIBLZF])
-m4trace:configure.ac:67: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBLZF])
-m4trace:configure.ac:67: -1- m4_pattern_allow([^HAVE_LIBLZF$])
-m4trace:configure.ac:68: -1- AH_OUTPUT([HAVE_LIBFASTLZ], [/* Define to 1 if you have the `fastlz\' library (-lfastlz). */
+m4trace:configure.ac:80: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBLZF])
+m4trace:configure.ac:80: -1- m4_pattern_allow([^HAVE_LIBLZF$])
+m4trace:configure.ac:81: -1- AH_OUTPUT([HAVE_LIBFASTLZ], [/* Define to 1 if you have the `fastlz\' library (-lfastlz). */
 @%:@undef HAVE_LIBFASTLZ])
-m4trace:configure.ac:68: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBFASTLZ])
-m4trace:configure.ac:68: -1- m4_pattern_allow([^HAVE_LIBFASTLZ$])
-m4trace:configure.ac:69: -1- AH_OUTPUT([HAVE_LIBQUICKLZ], [/* Define to 1 if you have the `quicklz\' library (-lquicklz). */
+m4trace:configure.ac:81: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBFASTLZ])
+m4trace:configure.ac:81: -1- m4_pattern_allow([^HAVE_LIBFASTLZ$])
+m4trace:configure.ac:82: -1- AH_OUTPUT([HAVE_LIBQUICKLZ], [/* Define to 1 if you have the `quicklz\' library (-lquicklz). */
 @%:@undef HAVE_LIBQUICKLZ])
-m4trace:configure.ac:69: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBQUICKLZ])
-m4trace:configure.ac:69: -1- m4_pattern_allow([^HAVE_LIBQUICKLZ$])
-m4trace:configure.ac:73: -1- AC_SUBST([ac_cv_have_stdint_h], [1])
-m4trace:configure.ac:73: -1- AC_SUBST_TRACE([ac_cv_have_stdint_h])
-m4trace:configure.ac:73: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
-m4trace:configure.ac:75: -1- AC_SUBST([ac_cv_have_stdint_h], [0])
-m4trace:configure.ac:75: -1- AC_SUBST_TRACE([ac_cv_have_stdint_h])
-m4trace:configure.ac:75: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
-m4trace:configure.ac:78: -1- AC_SUBST([ac_cv_have_stddef_h], [1])
-m4trace:configure.ac:78: -1- AC_SUBST_TRACE([ac_cv_have_stddef_h])
-m4trace:configure.ac:78: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
-m4trace:configure.ac:80: -1- AC_SUBST([ac_cv_have_stddef_h], [0])
-m4trace:configure.ac:80: -1- AC_SUBST_TRACE([ac_cv_have_stddef_h])
-m4trace:configure.ac:80: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
-m4trace:configure.ac:88: -1- AC_SUBST([SNAPPY_MAJOR])
-m4trace:configure.ac:88: -1- AC_SUBST_TRACE([SNAPPY_MAJOR])
-m4trace:configure.ac:88: -1- m4_pattern_allow([^SNAPPY_MAJOR$])
-m4trace:configure.ac:89: -1- AC_SUBST([SNAPPY_MINOR])
-m4trace:configure.ac:89: -1- AC_SUBST_TRACE([SNAPPY_MINOR])
-m4trace:configure.ac:89: -1- m4_pattern_allow([^SNAPPY_MINOR$])
-m4trace:configure.ac:90: -1- AC_SUBST([SNAPPY_PATCHLEVEL])
-m4trace:configure.ac:90: -1- AC_SUBST_TRACE([SNAPPY_PATCHLEVEL])
-m4trace:configure.ac:90: -1- m4_pattern_allow([^SNAPPY_PATCHLEVEL$])
-m4trace:configure.ac:91: -1- AC_SUBST([SNAPPY_LTVERSION], [1:0:0])
-m4trace:configure.ac:91: -1- AC_SUBST_TRACE([SNAPPY_LTVERSION])
-m4trace:configure.ac:91: -1- m4_pattern_allow([^SNAPPY_LTVERSION$])
-m4trace:configure.ac:93: -1- AC_CONFIG_HEADERS([config.h])
-m4trace:configure.ac:94: -1- AC_CONFIG_FILES([Makefile snappy-stubs-public.h])
-m4trace:configure.ac:95: -1- AC_SUBST([LIB@&t@OBJS], [$ac_libobjs])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([LIB@&t@OBJS])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^LIB@&t@OBJS$])
-m4trace:configure.ac:95: -1- AC_SUBST([LTLIBOBJS], [$ac_ltlibobjs])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([LTLIBOBJS])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^LTLIBOBJS$])
-m4trace:configure.ac:95: -1- AM_CONDITIONAL([am__EXEEXT], [test -n "$EXEEXT"])
-m4trace:configure.ac:95: -1- AC_SUBST([am__EXEEXT_TRUE])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([am__EXEEXT_TRUE])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^am__EXEEXT_TRUE$])
-m4trace:configure.ac:95: -1- AC_SUBST([am__EXEEXT_FALSE])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([am__EXEEXT_FALSE])
-m4trace:configure.ac:95: -1- m4_pattern_allow([^am__EXEEXT_FALSE$])
-m4trace:configure.ac:95: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_TRUE])
-m4trace:configure.ac:95: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_FALSE])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([top_builddir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([top_build_prefix])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([srcdir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([abs_srcdir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([top_srcdir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([abs_top_srcdir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([builddir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([abs_builddir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([abs_top_builddir])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([INSTALL])
-m4trace:configure.ac:95: -1- AC_SUBST_TRACE([MKDIR_P])
-m4trace:configure.ac:95: -1- AC_REQUIRE_AUX_FILE([ltmain.sh])
+m4trace:configure.ac:82: -1- AC_DEFINE_TRACE_LITERAL([HAVE_LIBQUICKLZ])
+m4trace:configure.ac:82: -1- m4_pattern_allow([^HAVE_LIBQUICKLZ$])
+m4trace:configure.ac:86: -1- AC_SUBST([ac_cv_have_stdint_h], [1])
+m4trace:configure.ac:86: -1- AC_SUBST_TRACE([ac_cv_have_stdint_h])
+m4trace:configure.ac:86: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
+m4trace:configure.ac:88: -1- AC_SUBST([ac_cv_have_stdint_h], [0])
+m4trace:configure.ac:88: -1- AC_SUBST_TRACE([ac_cv_have_stdint_h])
+m4trace:configure.ac:88: -1- m4_pattern_allow([^ac_cv_have_stdint_h$])
+m4trace:configure.ac:91: -1- AC_SUBST([ac_cv_have_stddef_h], [1])
+m4trace:configure.ac:91: -1- AC_SUBST_TRACE([ac_cv_have_stddef_h])
+m4trace:configure.ac:91: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
+m4trace:configure.ac:93: -1- AC_SUBST([ac_cv_have_stddef_h], [0])
+m4trace:configure.ac:93: -1- AC_SUBST_TRACE([ac_cv_have_stddef_h])
+m4trace:configure.ac:93: -1- m4_pattern_allow([^ac_cv_have_stddef_h$])
+m4trace:configure.ac:101: -1- AC_SUBST([SNAPPY_MAJOR])
+m4trace:configure.ac:101: -1- AC_SUBST_TRACE([SNAPPY_MAJOR])
+m4trace:configure.ac:101: -1- m4_pattern_allow([^SNAPPY_MAJOR$])
+m4trace:configure.ac:102: -1- AC_SUBST([SNAPPY_MINOR])
+m4trace:configure.ac:102: -1- AC_SUBST_TRACE([SNAPPY_MINOR])
+m4trace:configure.ac:102: -1- m4_pattern_allow([^SNAPPY_MINOR$])
+m4trace:configure.ac:103: -1- AC_SUBST([SNAPPY_PATCHLEVEL])
+m4trace:configure.ac:103: -1- AC_SUBST_TRACE([SNAPPY_PATCHLEVEL])
+m4trace:configure.ac:103: -1- m4_pattern_allow([^SNAPPY_PATCHLEVEL$])
+m4trace:configure.ac:104: -1- AC_SUBST([SNAPPY_LTVERSION], [1:0:0])
+m4trace:configure.ac:104: -1- AC_SUBST_TRACE([SNAPPY_LTVERSION])
+m4trace:configure.ac:104: -1- m4_pattern_allow([^SNAPPY_LTVERSION$])
+m4trace:configure.ac:106: -1- AC_CONFIG_HEADERS([config.h])
+m4trace:configure.ac:107: -1- AC_CONFIG_FILES([Makefile snappy-stubs-public.h])
+m4trace:configure.ac:108: -1- AC_SUBST([LIB@&t@OBJS], [$ac_libobjs])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([LIB@&t@OBJS])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^LIB@&t@OBJS$])
+m4trace:configure.ac:108: -1- AC_SUBST([LTLIBOBJS], [$ac_ltlibobjs])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([LTLIBOBJS])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^LTLIBOBJS$])
+m4trace:configure.ac:108: -1- AM_CONDITIONAL([am__EXEEXT], [test -n "$EXEEXT"])
+m4trace:configure.ac:108: -1- AC_SUBST([am__EXEEXT_TRUE])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([am__EXEEXT_TRUE])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^am__EXEEXT_TRUE$])
+m4trace:configure.ac:108: -1- AC_SUBST([am__EXEEXT_FALSE])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([am__EXEEXT_FALSE])
+m4trace:configure.ac:108: -1- m4_pattern_allow([^am__EXEEXT_FALSE$])
+m4trace:configure.ac:108: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_TRUE])
+m4trace:configure.ac:108: -1- _AM_SUBST_NOTMAKE([am__EXEEXT_FALSE])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([top_builddir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([top_build_prefix])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([srcdir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([abs_srcdir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([top_srcdir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([abs_top_srcdir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([builddir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([abs_builddir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([abs_top_builddir])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([INSTALL])
+m4trace:configure.ac:108: -1- AC_SUBST_TRACE([MKDIR_P])
+m4trace:configure.ac:108: -1- AC_REQUIRE_AUX_FILE([ltmain.sh])
diff --git a/configure b/configure
index a188774..b25a95e 100755
--- a/configure
+++ b/configure
@@ -884,6 +884,7 @@ enable_dependency_tracking
 with_gnu_ld
 enable_libtool_lock
 enable_gtest
+with_gflags
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1542,6 +1543,8 @@ Optional Packages:
   --with-pic              try to use only PIC/non-PIC objects [default=use
                           both]
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
+  --with-gflags           use Google Flags package to enhance the unit test
+                          [default=check]
 
 Some influential environment variables:
   CC          C compiler command
@@ -4741,13 +4744,13 @@ if test "${lt_cv_nm_interface+set}" = set; then :
 else
   lt_cv_nm_interface="BSD nm"
   echo "int some_variable = 0;" > conftest.$ac_ext
-  (eval echo "\"\$as_me:4744: $ac_compile\"" >&5)
+  (eval echo "\"\$as_me:4747: $ac_compile\"" >&5)
   (eval "$ac_compile" 2>conftest.err)
   cat conftest.err >&5
-  (eval echo "\"\$as_me:4747: $NM \\\"conftest.$ac_objext\\\"\"" >&5)
+  (eval echo "\"\$as_me:4750: $NM \\\"conftest.$ac_objext\\\"\"" >&5)
   (eval "$NM \"conftest.$ac_objext\"" 2>conftest.err > conftest.out)
   cat conftest.err >&5
-  (eval echo "\"\$as_me:4750: output\"" >&5)
+  (eval echo "\"\$as_me:4753: output\"" >&5)
   cat conftest.out >&5
   if $GREP 'External.*some_variable' conftest.out > /dev/null; then
     lt_cv_nm_interface="MS dumpbin"
@@ -5953,7 +5956,7 @@ ia64-*-hpux*)
   ;;
 *-*-irix6*)
   # Find out which ABI we are using.
-  echo '#line 5956 "configure"' > conftest.$ac_ext
+  echo '#line 5959 "configure"' > conftest.$ac_ext
   if { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_compile\""; } >&5
   (eval $ac_compile) 2>&5
   ac_status=$?
@@ -7479,11 +7482,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:7482: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:7485: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:7486: \$? = $ac_status" >&5
+   echo "$as_me:7489: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -7818,11 +7821,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:7821: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:7824: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:7825: \$? = $ac_status" >&5
+   echo "$as_me:7828: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -7923,11 +7926,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:7926: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:7929: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:7930: \$? = $ac_status" >&5
+   echo "$as_me:7933: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -7978,11 +7981,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:7981: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:7984: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:7985: \$? = $ac_status" >&5
+   echo "$as_me:7988: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -10362,7 +10365,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 10365 "configure"
+#line 10368 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -10458,7 +10461,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 10461 "configure"
+#line 10464 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -13344,11 +13347,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:13347: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:13350: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:13351: \$? = $ac_status" >&5
+   echo "$as_me:13354: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -13443,11 +13446,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:13446: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:13449: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:13450: \$? = $ac_status" >&5
+   echo "$as_me:13453: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -13495,11 +13498,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:13498: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:13501: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:13502: \$? = $ac_status" >&5
+   echo "$as_me:13505: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -14824,6 +14827,17 @@ fi
 
 
 
+# Check whether --with-gflags was given.
+if test "${with_gflags+set}" = set; then :
+  withval=$with_gflags;
+else
+  with_gflags=check
+fi
+
+
+if test "x$with_gflags" != "xno"; then
+
+
 if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
 	if test -n "$ac_tool_prefix"; then
   # Extract the first word of "${ac_tool_prefix}pkg-config", so it can be a program name with args.
@@ -14999,11 +15013,19 @@ fi
 
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
-                true # Ignore; we can live without it.
-
+                if test "x$with_gflags" != "xcheck"; then
+      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "--with-gflags was given, but test for gflags failed
+See \`config.log' for more details." "$LINENO" 5; }
+    fi
 elif test $pkg_failed = untried; then
-	true # Ignore; we can live without it.
-
+	if test "x$with_gflags" != "xcheck"; then
+      { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error "--with-gflags was given, but test for gflags failed
+See \`config.log' for more details." "$LINENO" 5; }
+    fi
 else
 	gflags_CFLAGS=$pkg_cv_gflags_CFLAGS
 	gflags_LIBS=$pkg_cv_gflags_LIBS
@@ -15013,6 +15035,7 @@ $as_echo "yes" >&6; }
 $as_echo "#define HAVE_GFLAGS 1" >>confdefs.h
 
 fi
+fi
 
 # See if we have __builtin_expect.
 # TODO: Use AC_CACHE.
diff --git a/configure.ac b/configure.ac
index 49d8cf5..3a3da35 100644
--- a/configure.ac
+++ b/configure.ac
@@ -21,10 +21,23 @@ AC_CHECK_HEADERS([stdint.h stddef.h])
 AC_CHECK_FUNC([mmap])
 
 GTEST_LIB_CHECK([], [true], [true # Ignore; we can live without it.])
-PKG_CHECK_MODULES([gflags], [libgflags],
+
+AC_ARG_WITH([gflags],
+  [AS_HELP_STRING(
+    [--with-gflags],
+    [use Google Flags package to enhance the unit test @<:@default=check@:>@])],
+    [],
+    [with_gflags=check])
+
+if test "x$with_gflags" != "xno"; then
+  PKG_CHECK_MODULES(
+    [gflags],
+    [libgflags],
     [AC_DEFINE([HAVE_GFLAGS], [1], [Use the gflags package for command-line parsing.])],
-    [true # Ignore; we can live without it.]
-)
+    [if test "x$with_gflags" != "xcheck"; then
+      AC_MSG_FAILURE([--with-gflags was given, but test for gflags failed])
+    fi])
+fi
 
 # See if we have __builtin_expect.
 # TODO: Use AC_CACHE.