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>
unsigned int num_fds;
int ready_out;
int wakefd;
- int out_fds[0];
+ int out_fds[];
};
struct receiver_context {
struct event_entry {
struct list_head node;
u32 tid;
- union perf_event event[0];
+ union perf_event event[];
};
static int output_bytes(struct perf_inject *inject, void *buf, size_t sz)
struct script_spec {
struct list_head node;
struct scripting_ops *ops;
- char spec[0];
+ char spec[];
};
static LIST_HEAD(script_specs);
struct sample_wrapper *next;
u64 timestamp;
- unsigned char data[0];
+ unsigned char data[];
};
#define TYPE_NONE 0
u32 idx;
int idx_asm;
int data_nr;
- struct annotation_data data[0];
+ struct annotation_data data[];
};
struct disasm_line {
struct sym_hist {
u64 nr_samples;
u64 period;
- struct sym_hist_entry addr[0];
+ struct sym_hist_entry addr[];
};
struct cyc_hist {
struct numa_topology {
u32 nr;
- struct numa_topology_node nodes[0];
+ struct numa_topology_node nodes[];
};
struct cpu_topology *cpu_topology__new(void);
struct rb_node rb_node;
u64 offset;
u64 size;
- char data[0];
+ char data[];
};
struct auxtrace_cache;
struct nsinfo *nsinfo;
struct dso_id id;
refcount_t refcnt;
- char name[0];
+ char name[];
};
/* dso__for_each_symbol - iterate over the symbols of given type
struct ip_callchain {
u64 nr;
- u64 ips[0];
+ u64 ips[];
};
struct branch_stack;
unsigned long vma;
unsigned int lineno;
/* The filename format is unspecified, absolute path, relative etc. */
- char const filename[0];
+ char const filename[];
};
struct jit_tool {
uint64_t addr;
int lineno; /* source line number starting at 1 */
int discrim; /* column discriminator, 0 is default */
- const char name[0]; /* null terminated filename, \xff\0 if same as previous entry */
+ const char name[]; /* null terminated filename, \xff\0 if same as previous entry */
};
struct jr_code_debug_info {
uint64_t code_addr;
uint64_t nr_entry;
- struct debug_entry entries[0];
+ struct debug_entry entries[];
};
struct jr_code_unwinding_info {
uint64_t unwinding_size;
uint64_t eh_frame_hdr_size;
uint64_t mapped_size;
- const char unwinding_data[0];
+ const char unwinding_data[];
};
union jr_entry {
struct ordered_events_buffer {
struct list_head list;
- struct ordered_event event[0];
+ struct ordered_event event[];
};
struct ordered_events {
struct pstack {
unsigned short top;
unsigned short max_nr_entries;
- void *entries[0];
+ void *entries[];
};
struct pstack *pstack__new(unsigned short max_nr_entries)
u8 inlined:1;
u8 arch_sym;
bool annotate2;
- char name[0];
+ char name[];
};
void symbol__delete(struct symbol *sym);
* encoded_t fde_addr;
* } binary_search_table[fde_count];
*/
- char data[0];
+ char data[];
} __packed;
static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
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