diff options
author | Gustavo A. R. Silva | 2020-05-07 13:57:55 -0500 |
---|---|---|
committer | Michael Ellerman | 2020-05-15 11:58:54 +1000 |
commit | 02bddf21c34d0a918acc8647195ba4507e3db8fc (patch) | |
tree | 1f9763895ecf57b6827836e695a1fd0eb5636bb2 /tools/testing/selftests/powerpc | |
parent | 0f6be41c60699fd8cdfa93e5e85a306cec1ac1d0 (diff) |
powerpc/mm: Replace zero-length array with flexible-array
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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200507185755.GA15014@embeddedor
Diffstat (limited to 'tools/testing/selftests/powerpc')
-rw-r--r-- | tools/testing/selftests/powerpc/pmu/ebb/trace.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/tools/testing/selftests/powerpc/pmu/ebb/trace.h b/tools/testing/selftests/powerpc/pmu/ebb/trace.h index 7c0fb5d2bdb1..da2a3be5441f 100644 --- a/tools/testing/selftests/powerpc/pmu/ebb/trace.h +++ b/tools/testing/selftests/powerpc/pmu/ebb/trace.h @@ -18,7 +18,7 @@ struct trace_entry { u8 type; u8 length; - u8 data[0]; + u8 data[]; }; struct trace_buffer @@ -26,7 +26,7 @@ struct trace_buffer u64 size; bool overflow; void *tail; - u8 data[0]; + u8 data[]; }; struct trace_buffer *trace_buffer_allocate(u64 size); |