btrfs-progs: ioctl: make build-time structure size checks optional

Temporarily make the build checks optional. The structure sizes could
change on arches due to alignment requirements or padding inserted into
the structures. We need more extensive tests to make sure we'd not break
ioctls.

Signed-off-by: David Sterba <dsterba@suse.com>

Makefile.in

@@ -19,6 +19,7 @@
 #                  all     - shortcut for all of the above
 #                  asan    - enable address sanitizer compiler feature
 #                  ubsan   - undefined behaviour sanitizer compiler feature
+#                  bcheck  - extended build checks
 #   W=123          build with warnings (default: off)
 #   DEBUG_CFLAGS   additional compiler flags for debugging build
 #   EXTRA_CFLAGS   additional compiler flags
@@ -161,6 +162,10 @@ ifneq (,$(findstring ubsan,$(D)))
   DEBUG_CFLAGS_INTERNAL += -fsanitize=undefined
 endif
 
+ifneq (,$(findstring bcheck,$(D)))
+  DEBUG_CFLAGS_INTERNAL += -DDEBUG_BUILD_CHECKS
+endif
+
 MAKEOPTS = --no-print-directory Q=$(Q)
 
 # build all by default

kerncompat.h

@@ -70,7 +70,11 @@
 
 #define __token_glue(a,b,c)	___token_glue(a,b,c)
 #define ___token_glue(a,b,c)	a ## b ## c
+#ifdef DEBUG_BUILD_CHECKS
 #define BUILD_ASSERT(x)		extern int __token_glue(compile_time_assert_,__LINE__,__COUNTER__)[1-2*!(x)] __attribute__((unused))
+#else
+#define BUILD_ASSERT(x)
+#endif
 
 #ifndef BTRFS_DISABLE_BACKTRACE
 #define MAX_BACKTRACE	16