diff --git a/m4/sah_select_bitness.m4 b/m4/sah_select_bitness.m4
index 57be329ce5..3f80dfacde 100644
--- a/m4/sah_select_bitness.m4
+++ b/m4/sah_select_bitness.m4
@@ -7,15 +7,17 @@ AC_DEFUN([SAH_DEFAULT_BITNESS],[
       ${CC} ${CFLAGS} ${CPPFLAGS} -fno-lto -c conftest.$ac_ext 2>&AS_MESSAGE_LOG_FD >&AS_MESSAGE_LOG_FD
       COMPILER_MODEL_BITS=32
       if test -f conftest.${OBJEXT}; then
-        if test -n "$(${OBJDUMP} --file-headers conftest.${OBJEXT} | grep 'file format' | grep 64)" -o -n "$(file conftest.${OBJEXT} | grep -i 64-bit)"; then
+        OBJDUMP_TEST="$(${OBJDUMP} --file-headers conftest.${OBJEXT} | grep 'file format')"
+        FILE_TEST="$(file conftest.${OBJEXT})"
+        if test -n "$(echo $OBJDUMP_TEST | grep 64)" -o -n "$(echo $FILE_TEST | grep -i 64-bit)"; then
           COMPILER_MODEL_BITS=64
         #else
-          #if test -n "$(${OBJDUMP} --file-headers conftest.${OBJEXT} | grep 'file format' | grep 16)"; then
+          #if test -n "$(echo $OBJDUMP_TEST | grep 16)"; then
             #COMPILER_MODEL_BITS=16
           #fi
         fi
       fi
-      /bin/rm conftest.$ac_ext conftest.${OBJEXT}
+      /bin/rm -f conftest.$ac_ext conftest.${OBJEXT}
       AC_MSG_RESULT([$COMPILER_MODEL_BITS])
     AC_LANG_POP([C])
 
@@ -25,13 +27,20 @@ AC_DEFUN([SAH_DEFAULT_BITNESS],[
       AC_REQUIRE_CPP
       ${CXX} ${CXXFLAGS} ${CPPFLAGS} -fno-lto -c conftest.$ac_ext 2>&AS_MESSAGE_LOG_FD >&AS_MESSAGE_LOG_FD
       if test -f conftest.${OBJEXT}; then
-        if test -n "$(${OBJDUMP} --file-headers conftest.${OBJEXT} | grep 'file format' | grep 64)" -o -n "$(file conftest.${OBJEXT} | grep -i 64-bit)"; then
+        OBJDUMP_TEST="$(${OBJDUMP} --file-headers conftest.${OBJEXT} | grep 'file format')"
+        FILE_TEST="$(file conftest.${OBJEXT})"
+        if test -n "$(echo $OBJDUMP_TEST | grep 32)" -o -n "$(echo $FILE_TEST | grep -i 32-bit)"; then
+          if test "${COMPILER_MODEL_BITS}" != "32"; then
+            AC_MSG_ERROR([32 but not same as bitness in C])
+          fi
+        fi
+        if test -n "$(echo $OBJDUMP_TEST | grep 64)" -o -n "$(echo $FILE_TEST | grep -i 64-bit)"; then
           if test "${COMPILER_MODEL_BITS}" != "64"; then
             AC_MSG_ERROR([64 but not same as bitness in C])
           fi
         fi
       fi
-      /bin/rm conftest.$ac_ext conftest.${OBJEXT}
+      /bin/rm -f conftest.$ac_ext conftest.${OBJEXT}
       AC_MSG_RESULT([$COMPILER_MODEL_BITS])
     AC_LANG_POP([C++])
   fi
@@ -47,14 +56,15 @@ AC_DEFUN([SAH_SELECT_BITNESS],[
       AC_REQUIRE_CPP
       ${CC} ${CFLAGS} ${CPPFLAGS} -m$1 -fno-lto -c conftest.$ac_ext 2>&AS_MESSAGE_LOG_FD >&AS_MESSAGE_LOG_FD
       if test -f conftest.${OBJEXT}; then
-        if test -n "$(file conftest.${OBJEXT} | grep -i $1-bit)"; then
+        FILE_TEST="$(file conftest.${OBJEXT})"
+        if test -n "$(echo $FILE_TEST | grep -i $1-bit)"; then
           CFLAGS="${CFLAGS} -m$1"
           AC_MSG_RESULT([ok use $1])
         else
           AC_MSG_ERROR([failed still $COMPILER_MODEL_BITS])
         fi
       fi
-      /bin/rm conftest.$ac_ext conftest.${OBJEXT}
+      /bin/rm -f conftest.$ac_ext conftest.${OBJEXT}
     else
       AC_MSG_RESULT([ok use $1])
     fi
@@ -67,14 +77,15 @@ AC_DEFUN([SAH_SELECT_BITNESS],[
       AC_REQUIRE_CPP
       ${CXX} ${CXXFLAGS} ${CPPFLAGS} -m$1 -fno-lto -c conftest.$ac_ext 2>&AS_MESSAGE_LOG_FD >&AS_MESSAGE_LOG_FD
       if test -f conftest.${OBJEXT}; then
-        if test -n "$(file conftest.${OBJEXT} | grep -i $1-bit)"; then
+        FILE_TEST="$(file conftest.${OBJEXT})"
+        if test -n "$(echo $FILE_TEST | grep -i $1-bit)"; then
           CXXFLAGS="${CXXFLAGS} -m$1"
           AC_MSG_RESULT([ok use $1])
         else
           AC_MSG_ERROR([failed still $COMPILER_MODEL_BITS])
         fi
       fi
-      /bin/rm conftest.$ac_ext conftest.${OBJEXT}
+      /bin/rm -f conftest.$ac_ext conftest.${OBJEXT}
     else
       AC_MSG_RESULT([ok use $1])
     fi