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author | 2020-05-15 12:29:26 -0500 | |
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committer | 2020-05-28 10:03:27 -0300 | |
commit | 6549a8c0c3d94500a9a1bb66fc237f7c01c41753 (patch) | |
tree | 003129d2a7b9d34ac57d28ca54745dae234c65c9 /tools/perf/util/annotate.h | |
parent | perf intel-pt: Use allocated branch stack for PEBS sample (diff) | |
download | linux-6549a8c0c3d94500a9a1bb66fc237f7c01c41753.tar.gz linux-6549a8c0c3d94500a9a1bb66fc237f7c01c41753.tar.bz2 linux-6549a8c0c3d94500a9a1bb66fc237f7c01c41753.zip |
perf tools: 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>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200515172926.GA31976@embeddedor
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/annotate.h')
-rw-r--r-- | tools/perf/util/annotate.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h index 2d88069d6428..0a0cd4f32175 100644 --- a/tools/perf/util/annotate.h +++ b/tools/perf/util/annotate.h @@ -144,7 +144,7 @@ struct annotation_line { u32 idx; int idx_asm; int data_nr; - struct annotation_data data[0]; + struct annotation_data data[]; }; struct disasm_line { @@ -227,7 +227,7 @@ void symbol__calc_percent(struct symbol *sym, struct evsel *evsel); struct sym_hist { u64 nr_samples; u64 period; - struct sym_hist_entry addr[0]; + struct sym_hist_entry addr[]; }; struct cyc_hist { |