Do not override CFLAGS, as CFLAGS is a user flag.

* Furthermore, use NDEBUG globally to detect the presence
  of building with more debug output information.
  AX_CHECK_ENABLE_DEBUG is easier to use, and nowadays
  Gnome has also switched to it from its own custom solution.

Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>

1 files changed, 124 insertions, 0 deletions

diff --git a/m4/ax_check_enable_debug.m4 b/m4/ax_check_enable_debug.m4
new file mode 100644
index 00000000..f99d75fe
--- /dev/null
+++ b/m4/ax_check_enable_debug.m4
@@ -0,0 +1,124 @@
+# ===========================================================================
+#   http://www.gnu.org/software/autoconf-archive/ax_check_enable_debug.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_ENABLE_DEBUG([enable by default=yes/info/profile/no], [ENABLE DEBUG VARIABLES ...], [DISABLE DEBUG VARIABLES NDEBUG ...], [IS-RELEASE])
+#
+# DESCRIPTION
+#
+#   Check for the presence of an --enable-debug option to configure, with
+#   the specified default value used when the option is not present.  Return
+#   the value in the variable $ax_enable_debug.
+#
+#   Specifying 'yes' adds '-g -O0' to the compilation flags for all
+#   languages. Specifying 'info' adds '-g' to the compilation flags.
+#   Specifying 'profile' adds '-g -pg' to the compilation flags and '-pg' to
+#   the linking flags. Otherwise, nothing is added.
+#
+#   Define the variables listed in the second argument if debug is enabled,
+#   defaulting to no variables.  Defines the variables listed in the third
+#   argument if debug is disabled, defaulting to NDEBUG.  All lists of
+#   variables should be space-separated.
+#
+#   If debug is not enabled, ensure AC_PROG_* will not add debugging flags.
+#   Should be invoked prior to any AC_PROG_* compiler checks.
+#
+#   IS-RELEASE can be used to change the default to 'no' when making a
+#   release.  Set IS-RELEASE to 'yes' or 'no' as appropriate. By default, it
+#   uses the value of $ax_is_release, so if you are using the AX_IS_RELEASE
+#   macro, there is no need to pass this parameter.
+#
+#     AX_IS_RELEASE([git-directory])
+#     AX_CHECK_ENABLE_DEBUG()
+#
+# LICENSE
+#
+#   Copyright (c) 2011 Rhys Ulerich <rhys.ulerich@gmail.com>
+#   Copyright (c) 2014, 2015 Philip Withnall <philip@tecnocode.co.uk>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.
+
+#serial 5
+
+AC_DEFUN([AX_CHECK_ENABLE_DEBUG],[
+    AC_BEFORE([$0],[AC_PROG_CC])dnl
+    AC_BEFORE([$0],[AC_PROG_CXX])dnl
+    AC_BEFORE([$0],[AC_PROG_F77])dnl
+    AC_BEFORE([$0],[AC_PROG_FC])dnl
+
+    AC_MSG_CHECKING(whether to enable debugging)
+
+    ax_enable_debug_default=m4_tolower(m4_normalize(ifelse([$1],,[no],[$1])))
+    ax_enable_debug_is_release=m4_tolower(m4_normalize(ifelse([$4],,
+                                                              [$ax_is_release],
+                                                              [$4])))
+
+    # If this is a release, override the default.
+    AS_IF([test "$ax_enable_debug_is_release" = "yes"],
+      [ax_enable_debug_default="no"])
+
+    m4_define(ax_enable_debug_vars,[m4_normalize(ifelse([$2],,,[$2]))])
+    m4_define(ax_disable_debug_vars,[m4_normalize(ifelse([$3],,[NDEBUG],[$3]))])
+
+    AC_ARG_ENABLE(debug,
+	[AS_HELP_STRING([--enable-debug=]@<:@yes/info/profile/no@:>@,[compile with debugging])],
+	[],enable_debug=$ax_enable_debug_default)
+
+    # empty mean debug yes
+    AS_IF([test "x$enable_debug" = "x"],
+      [enable_debug="yes"])
+
+    # case of debug
+    AS_CASE([$enable_debug],
+      [yes],[
+	AC_MSG_RESULT(yes)
+	CFLAGS="${CFLAGS} -g -O0"
+	CXXFLAGS="${CXXFLAGS} -g -O0"
+	FFLAGS="${FFLAGS} -g -O0"
+	FCFLAGS="${FCFLAGS} -g -O0"
+	OBJCFLAGS="${OBJCFLAGS} -g -O0"
+      ],
+      [info],[
+	AC_MSG_RESULT(info)
+	CFLAGS="${CFLAGS} -g"
+	CXXFLAGS="${CXXFLAGS} -g"
+	FFLAGS="${FFLAGS} -g"
+	FCFLAGS="${FCFLAGS} -g"
+	OBJCFLAGS="${OBJCFLAGS} -g"
+      ],
+      [profile],[
+	AC_MSG_RESULT(profile)
+	CFLAGS="${CFLAGS} -g -pg"
+	CXXFLAGS="${CXXFLAGS} -g -pg"
+	FFLAGS="${FFLAGS} -g -pg"
+	FCFLAGS="${FCFLAGS} -g -pg"
+	OBJCFLAGS="${OBJCFLAGS} -g -pg"
+	LDFLAGS="${LDFLAGS} -pg"
+      ],
+      [
+	AC_MSG_RESULT(no)
+	dnl Ensure AC_PROG_CC/CXX/F77/FC/OBJC will not enable debug flags
+	dnl by setting any unset environment flag variables
+	AS_IF([test "x${CFLAGS+set}" != "xset"],
+	  [CFLAGS=""])
+	AS_IF([test "x${CXXFLAGS+set}" != "xset"],
+	  [CXXFLAGS=""])
+	AS_IF([test "x${FFLAGS+set}" != "xset"],
+	  [FFLAGS=""])
+	AS_IF([test "x${FCFLAGS+set}" != "xset"],
+	  [FCFLAGS=""])
+	AS_IF([test "x${OBJCFLAGS+set}" != "xset"],
+	  [OBJCFLAGS=""])
+      ])
+
+    dnl Define various variables if debugging is disabled.
+    dnl assert.h is a NOP if NDEBUG is defined, so define it by default.
+    AS_IF([test "x$enable_debug" = "xyes"],
+      [m4_map_args_w(ax_enable_debug_vars, [AC_DEFINE(], [,,[Define if debugging is enabled])])],
+      [m4_map_args_w(ax_disable_debug_vars, [AC_DEFINE(], [,,[Define if debugging is disabled])])])
+    ax_enable_debug=$enable_debug
+])