| Message ID | 20200507185408.GA14561@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915/gt: Replace zero-length array with flexible-array | expand |
diff --git a/drivers/gpu/drm/i915/display/intel_vbt_defs.h b/drivers/gpu/drm/i915/display/intel_vbt_defs.h index 05c7cbe32eb4..aef7fe932d1a 100644 --- a/drivers/gpu/drm/i915/display/intel_vbt_defs.h +++ b/drivers/gpu/drm/i915/display/intel_vbt_defs.h @@ -462,7 +462,7 @@ struct bdb_general_definitions { * number = (block_size - sizeof(bdb_general_definitions))/ * defs->child_dev_size; */ - u8 devices[0]; + u8 devices[]; } __packed; /* @@ -839,7 +839,7 @@ struct bdb_mipi_config { struct bdb_mipi_sequence { u8 version; - u8 data[0]; /* up to 6 variable length blocks */ + u8 data[]; /* up to 6 variable length blocks */ } __packed; /* diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 683014e7bc51..f42c99da2580 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -216,7 +216,7 @@ struct virtual_engine { /* And finally, which physical engines this virtual engine maps onto. */ unsigned int num_siblings; - struct intel_engine_cs *siblings[0]; + struct intel_engine_cs *siblings[]; }; static struct virtual_engine *to_virtual_engine(struct intel_engine_cs *engine) diff --git a/drivers/gpu/drm/i915/i915_gpu_error.h b/drivers/gpu/drm/i915/i915_gpu_error.h index 0d1f6c8ff355..5a6561f7a210 100644 --- a/drivers/gpu/drm/i915/i915_gpu_error.h +++ b/drivers/gpu/drm/i915/i915_gpu_error.h @@ -42,7 +42,7 @@ struct i915_vma_coredump { int num_pages; int page_count; int unused; - u32 *pages[0]; + u32 *pages[]; }; struct i915_request_coredump {
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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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 <gustavoars@kernel.org> --- 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 +- 3 files changed, 4 insertions(+), 4 deletions(-)