build: Decontaminate enviromental pollution to allow compiliation by clang

The statements in configure.ac "pollute" the environmental variables. This causes problem
when --enable-warnings is set and clang is the compiler. It only works by accident on
gcc because gcc aborts on illegal flags anyway, but clang does not which causes -Werror
to get added to the check. One of the warning conflicts with that, causing it to be
uncompiliable under clang.

This patch removes the  environmental polluation by storing the flags in automake variables.
The flags are then added by automake. Also, there already a function in autoconf-archive to
determine valid flags, so use that instead of the hand-rolled one.

Signed-off-by: Christopher Byrne <salah.coronya@gmail.com>

Author: salahcoronya

common/Makefile.am

@@ -20,7 +20,7 @@
 noinst_LIBRARIES = libtio.a libprot.a libdict.a libexpr.a
 
 AM_CPPFLAGS=-I$(top_srcdir)
-AM_CFLAGS = $(PIC_CFLAGS)
+AM_CFLAGS = $(PIC_CFLAGS) $(DEBUG_CFLAGS) $(EXTRA_CFLAGS)
 
 libtio_a_SOURCES = tio.c tio.h
 

compat/Makefile.am

@@ -20,7 +20,7 @@
 noinst_LIBRARIES = libcompat.a
 
 AM_CPPFLAGS=-I$(top_srcdir)
-AM_CFLAGS = $(PIC_CFLAGS)
+AM_CFLAGS = $(PIC_CFLAGS) $(DEBUG_CFLAGS) $(EXTRA_CFLAGS)
 
 EXTRA_DIST = getopt_long.c getopt_long.h \
              ether.c ether.h \

configure.ac

@@ -101,39 +101,25 @@ then
 fi
 
 # check for debugging options
+DEBUG_CFLAGS=""
 AC_ARG_ENABLE(debug,
               AS_HELP_STRING([--enable-debug],
                              [enable extensive debugging and logging]),
-              [if test "x$enableval" != "xno" ; then CFLAGS="-g -DDEBUG $CFLAGS" ; fi])
+              [AS_IF([test "x$enableval" != "xno"],
+		    [AX_APPEND_COMPILE_FLAGS([-g -DDEBUG],[DEBUG_CFLAGS])]
+              )])
+AC_SUBST([DEBUG_CFLAGS])
 
 # check for extra compiler warnings
-DESIRED_CFLAGS=""
+EXTRA_CFLAGS=""
 AC_ARG_ENABLE(warnings,
               AS_HELP_STRING([--enable-warnings],
                              [enable extra compiler warnings (gcc)]),
-              [if test "x$enableval" != "no"
-               then
-                 CFLAGS="$CFLAGS -pedantic -Wall -Wshadow -Wpointer-arith -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Waggregate-return -Wmissing-declarations -Wunused -Wformat=2 -Wswitch-default -Wswitch-enum -Wfloat-equal -Wbad-function-cast -Wredundant-decls"
-                 DESIRED_CFLAGS="$DESIRED_CFLAGS -Wextra -Wdeclaration-after-statement -Werror-implicit-function-declaration -Werror=implicit"
-               fi])
-test_gcc_flag() {
-  AC_LANG_CONFTEST([AC_LANG_PROGRAM()])
-  $CC -c conftest.c $CFLAGS $@ > /dev/null 2> /dev/null
-  ret=$?
-  rm -f conftest.o
-  return $ret
-}
-for flag in $DESIRED_CFLAGS
-do
-  AC_MSG_CHECKING([whether $CC accepts $flag])
-  if test_gcc_flag $flag
-  then
-    CFLAGS="$CFLAGS $flag"
-    AC_MSG_RESULT([yes])
-  else
-    AC_MSG_RESULT([no])
-  fi
-done
+              [AS_IF([test "x$enableval" != "xno"],[
+                 AX_APPEND_COMPILE_FLAGS([-pedantic -Wall -Wshadow -Wpointer-arith -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Waggregate-return -Wmissing-declarations -Wunused -Wformat=2 -Wswitch-default -Wswitch-enum -Wfloat-equal -Wbad-function-cast -Wredundant-decls],[EXTRA_CFLAGS],[-Werror])
+                 AX_APPEND_COMPILE_FLAGS([-Wextra -Wdeclaration-after-statement -Werror-implicit-function-declaration -Werror=implicit],[EXTRA_CFLAGS],[-Werror])
+               ])])
+AC_SUBST([EXTRA_CFLAGS])
 
 # check for Position Independent Code compiler option
 PIC_CFLAGS=""

nslcd/Makefile.am

@@ -21,7 +21,7 @@
 sbin_PROGRAMS = nslcd
 
 AM_CPPFLAGS=-I$(top_srcdir)
-AM_CFLAGS = $(PTHREAD_CFLAGS)
+AM_CFLAGS = $(PTHREAD_CFLAGS) $(DEBUG_CFLAGS) $(EXTRA_CFLAGS)
 
 nslcd_SOURCES = nslcd.c ../nslcd.h ../common/nslcd-prot.h \
                 ../compat/attrs.h \

nss/Makefile.am

@@ -23,7 +23,7 @@
 noinst_PROGRAMS = nss_ldap.so
 
 AM_CPPFLAGS=-I$(top_srcdir)
-AM_CFLAGS = $(PIC_CFLAGS)
+AM_CFLAGS = $(PIC_CFLAGS) $(DEBUG_CFLAGS) $(EXTRA_CFLAGS)
 
 nss_ldap_so_SOURCES = common.c common.h prototypes.h solnss.h \
                       ../nslcd.h ../common/nslcd-prot.h \

pam/Makefile.am

@@ -21,7 +21,7 @@
 noinst_PROGRAMS = pam_ldap.so
 
 AM_CPPFLAGS=-I$(top_srcdir)
-AM_CFLAGS = $(PIC_CFLAGS)
+AM_CFLAGS = $(PIC_CFLAGS) $(DEBUG_CFLAGS) $(EXTRA_CFLAGS)
 
 pam_ldap_so_SOURCES = ../nslcd.h ../common/nslcd-prot.h \
                       ../compat/attrs.h pam.c common.h

tests/Makefile.am

@@ -58,7 +58,7 @@ clean-local:
 	-rm -rf *.pyc *.pyo __pycache__ flake8-venv
 
 AM_CPPFLAGS = -I$(top_srcdir)
-AM_CFLAGS = $(PTHREAD_CFLAGS) -g
+AM_CFLAGS = $(PTHREAD_CFLAGS) -g $(DEBUG_CFLAGS) $(EXTRA_CFLAGS)
 
 test_dict_SOURCES = test_dict.c ../common/dict.h
 test_dict_LDADD = ../common/libdict.a