On Tue, 25 Feb 2020, "Gustavo A. R. Silva" gustavo@embeddedor.com wrote:
The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99:
struct foo { int stuff; struct boo array[]; };
By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this change:
"Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com
drivers/gpu/drm/etnaviv/etnaviv_gem.h | 2 +- drivers/gpu/drm/gma500/intel_bios.h | 2 +- drivers/gpu/drm/i915/display/intel_vbt_defs.h | 4 ++-- drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +- drivers/gpu/drm/i915/i915_gpu_error.h | 2 +-
Please split out the i915 changes to a separate patch.
drivers/gpu/drm/msm/msm_gem.h | 2 +- drivers/gpu/drm/qxl/qxl_cmd.c | 2 +- drivers/gpu/drm/vboxvideo/vboxvideo.h | 2 +- drivers/gpu/drm/vc4/vc4_drv.h | 2 +- drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 2 +- drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 2 +- include/drm/bridge/mhl.h | 4 ++-- include/drm/drm_displayid.h | 2 +- include/uapi/drm/i915_drm.h | 4 ++--
Not sure it's worth touching uapi headers. They're full of both [0] and []. Again, please at least split it to a separate patch to be decided separately.
BR, Jani.