config: Check for and use gcc -Wnull-dereference.

-Wnull-dereference is new in GCC6

Signed-off-by: Mark Wielaard <mjw@redhat.com>

diff --git a/ChangeLog b/ChangeLog
index dce61adf53f95655ccdefbf806083929e38696f7..07b525c38809455813706351e029167f6d6be22c 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2016-02-13  Mark Wielaard  <mjw@redhat.com>
+
+       * configure.ac: Add check for whether gcc accepts -Wnull-dereference.
+
 2016-02-08  Mark Wielaard  <mjw@redhat.com>
 
        * configure.ac: Add checks for sane -Wlogical-op and whether gcc

diff --git a/config/ChangeLog b/config/ChangeLog
index 8523cb31751e6f553ffa1aa2224cb1cc6a36738d..494778a424876119ad4a67342b1f1be0fe3ca0f2 100644 (file)
--- a/config/ChangeLog
+++ b/config/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-13  Mark Wielaard  <mjw@redhat.com>
+
+       * eu.am: Check HAVE_NULL_DEREFERENCE_WARNING.
+       (AM_CFLAGS): Add NULL_DEREFERENCE_WARNING.
+
 2016-02-09  Mark Wielaard  <mjw@redhat.com>
 
        * eu.am: Check SANE_LOGICAL_OP_WARNING and

diff --git a/config/eu.am b/config/eu.am
index c4e9279adc164052d415898b75d124026926fd3d..4998771dc115e90aa92193efbf3e6779963bba58 100644 (file)
--- a/config/eu.am
+++ b/config/eu.am
@@ -55,9 +55,16 @@ else
 DUPLICATED_COND_WARNING=
 endif
 
+if HAVE_NULL_DEREFERENCE_WARNING
+NULL_DEREFERENCE_WARNING=-Wnull-dereference
+else
+NULL_DEREFERENCE_WARNING=
+endif
+
 AM_CFLAGS = -std=gnu99 -Wall -Wshadow -Wformat=2 \
            -Wold-style-definition -Wstrict-prototypes \
            $(LOGICAL_OP_WARNING) $(DUPLICATED_COND_WARNING) \
+           $(NULL_DEREFERENCE_WARNING) \
            $(if $($(*F)_no_Werror),,-Werror) \
            $(if $($(*F)_no_Wunused),,-Wunused -Wextra) \
            $(if $($(*F)_no_Wstack_usage),,$(STACK_USAGE_WARNING)) \

diff --git a/configure.ac b/configure.ac
index d447db7e1009998c3f6086cb30458bee1f49d7bb..df58b5b9a8435f489941a7842329f70b338ab029 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -313,6 +313,16 @@ CFLAGS="$old_CFLAGS"])
 AM_CONDITIONAL(HAVE_DUPLICATED_COND_WARNING,
               [test "x$ac_cv_duplicated_cond" != "xno"])
 
+# -Wnull-dereference was added by GCC6
+AC_CACHE_CHECK([whether gcc accepts -Wnull-dereference], ac_cv_null_dereference, [dnl
+old_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -Wnull-dereference"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([])],
+                 ac_cv_null_dereference=yes, ac_cv_null_dereference=no)
+CFLAGS="$old_CFLAGS"])
+AM_CONDITIONAL(HAVE_NULL_DEREFERENCE_WARNING,
+              [test "x$ac_cv_null_dereference" != "xno"])
+
 dnl Check if we have argp available from our libc
 AC_LINK_IFELSE(
        [AC_LANG_PROGRAM(