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R. Silva" Cc: Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: Re: [PATCH v2 perf/core] perf tools: Replace zero-length array with flexible-array Message-ID: <20200520014209.GG28228@kernel.org> References: <20200515172926.GA31976@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200515172926.GA31976@embeddedor> X-Url: http://acmel.wordpress.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, May 15, 2020 at 12:29:26PM -0500, Gustavo A. R. Silva escreveu: > 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[]; > }; Thanks, applied. - Arnaldo > 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 > --- > Changes in v2: > - Remove changes in tools/perf/util/branch.h > > tools/perf/bench/sched-messaging.c | 2 +- > tools/perf/builtin-inject.c | 2 +- > tools/perf/builtin-script.c | 2 +- > tools/perf/builtin-timechart.c | 2 +- > tools/perf/util/annotate.h | 4 ++-- > tools/perf/util/cputopo.h | 2 +- > tools/perf/util/dso.h | 4 ++-- > tools/perf/util/event.h | 2 +- > tools/perf/util/jitdump.c | 2 +- > tools/perf/util/jitdump.h | 6 +++--- > tools/perf/util/ordered-events.h | 2 +- > tools/perf/util/pstack.c | 2 +- > tools/perf/util/symbol.h | 2 +- > tools/perf/util/unwind-libunwind-local.c | 2 +- > 14 files changed, 18 insertions(+), 18 deletions(-) > > diff --git a/tools/perf/bench/sched-messaging.c b/tools/perf/bench/sched-messaging.c > index 97e4a4fb33624..71d830d7b9231 100644 > --- a/tools/perf/bench/sched-messaging.c > +++ b/tools/perf/bench/sched-messaging.c > @@ -40,7 +40,7 @@ struct sender_context { > unsigned int num_fds; > int ready_out; > int wakefd; > - int out_fds[0]; > + int out_fds[]; > }; > > struct receiver_context { > diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c > index 53932db97a79d..4a6de4b03ac0b 100644 > --- a/tools/perf/builtin-inject.c > +++ b/tools/perf/builtin-inject.c > @@ -51,7 +51,7 @@ struct perf_inject { > 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) > diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c > index ecc8bd4c5e57d..4c0837efaceba 100644 > --- a/tools/perf/builtin-script.c > +++ b/tools/perf/builtin-script.c > @@ -2449,7 +2449,7 @@ static int __cmd_script(struct perf_script *script) > struct script_spec { > struct list_head node; > struct scripting_ops *ops; > - char spec[0]; > + char spec[]; > }; > > static LIST_HEAD(script_specs); > diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c > index c76f84b174c4b..4e380e7b52307 100644 > --- a/tools/perf/builtin-timechart.c > +++ b/tools/perf/builtin-timechart.c > @@ -128,7 +128,7 @@ struct sample_wrapper { > struct sample_wrapper *next; > > u64 timestamp; > - unsigned char data[0]; > + unsigned char data[]; > }; > > #define TYPE_NONE 0 > diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h > index 2d88069d64283..0a0cd4f32175e 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 { > diff --git a/tools/perf/util/cputopo.h b/tools/perf/util/cputopo.h > index 7bf6b811f715e..6201c3790d868 100644 > --- a/tools/perf/util/cputopo.h > +++ b/tools/perf/util/cputopo.h > @@ -22,7 +22,7 @@ struct numa_topology_node { > > struct numa_topology { > u32 nr; > - struct numa_topology_node nodes[0]; > + struct numa_topology_node nodes[]; > }; > > struct cpu_topology *cpu_topology__new(void); > diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h > index 9553a1fd9e8a8..e3e9e3b772970 100644 > --- a/tools/perf/util/dso.h > +++ b/tools/perf/util/dso.h > @@ -137,7 +137,7 @@ struct dso_cache { > struct rb_node rb_node; > u64 offset; > u64 size; > - char data[0]; > + char data[]; > }; > > struct auxtrace_cache; > @@ -209,7 +209,7 @@ struct dso { > 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 > diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h > index b8289f160f070..6ae01c3c2ffa7 100644 > --- a/tools/perf/util/event.h > +++ b/tools/perf/util/event.h > @@ -79,7 +79,7 @@ struct sample_read { > > struct ip_callchain { > u64 nr; > - u64 ips[0]; > + u64 ips[]; > }; > > struct branch_stack; > diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c > index e3ccb0ce1938d..32bb05e03fb2d 100644 > --- a/tools/perf/util/jitdump.c > +++ b/tools/perf/util/jitdump.c > @@ -57,7 +57,7 @@ struct debug_line_info { > 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 { > diff --git a/tools/perf/util/jitdump.h b/tools/perf/util/jitdump.h > index f2c3823cc81a4..ab2842def83df 100644 > --- a/tools/perf/util/jitdump.h > +++ b/tools/perf/util/jitdump.h > @@ -93,7 +93,7 @@ struct debug_entry { > 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 { > @@ -101,7 +101,7 @@ 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 { > @@ -110,7 +110,7 @@ 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 { > diff --git a/tools/perf/util/ordered-events.h b/tools/perf/util/ordered-events.h > index 0920fb0ec6cc7..75345946c4b9e 100644 > --- a/tools/perf/util/ordered-events.h > +++ b/tools/perf/util/ordered-events.h > @@ -29,7 +29,7 @@ typedef int (*ordered_events__deliver_t)(struct ordered_events *oe, > > struct ordered_events_buffer { > struct list_head list; > - struct ordered_event event[0]; > + struct ordered_event event[]; > }; > > struct ordered_events { > diff --git a/tools/perf/util/pstack.c b/tools/perf/util/pstack.c > index 80ff41fc45be8..a1d1e4ef6257e 100644 > --- a/tools/perf/util/pstack.c > +++ b/tools/perf/util/pstack.c > @@ -15,7 +15,7 @@ > struct pstack { > unsigned short top; > unsigned short max_nr_entries; > - void *entries[0]; > + void *entries[]; > }; > > struct pstack *pstack__new(unsigned short max_nr_entries) > diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h > index 93fc43db1be3c..ff4f4c47e1484 100644 > --- a/tools/perf/util/symbol.h > +++ b/tools/perf/util/symbol.h > @@ -55,7 +55,7 @@ struct symbol { > u8 inlined:1; > u8 arch_sym; > bool annotate2; > - char name[0]; > + char name[]; > }; > > void symbol__delete(struct symbol *sym); > diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c > index b4649f5a0c2f1..9aededc0bc06f 100644 > --- a/tools/perf/util/unwind-libunwind-local.c > +++ b/tools/perf/util/unwind-libunwind-local.c > @@ -243,7 +243,7 @@ struct eh_frame_hdr { > * 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, > -- > 2.26.2 > -- - Arnaldo