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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 7649773293 ("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>
35 lines
665 B
C
35 lines
665 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __PERF_CPUTOPO_H
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#define __PERF_CPUTOPO_H
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#include <linux/types.h>
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struct cpu_topology {
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u32 core_sib;
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u32 die_sib;
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u32 thread_sib;
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char **core_siblings;
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char **die_siblings;
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char **thread_siblings;
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};
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struct numa_topology_node {
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char *cpus;
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u32 node;
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u64 mem_total;
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u64 mem_free;
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};
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struct numa_topology {
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u32 nr;
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struct numa_topology_node nodes[];
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};
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struct cpu_topology *cpu_topology__new(void);
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void cpu_topology__delete(struct cpu_topology *tp);
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struct numa_topology *numa_topology__new(void);
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void numa_topology__delete(struct numa_topology *tp);
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#endif /* __PERF_CPUTOPO_H */
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