Messages in this thread | | | Date | Mon, 11 May 2020 17:20:08 -0300 | Subject | Re: [PATCH] perf tools: Replace zero-length array with flexible-array | From | Arnaldo Melo <> |
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On May 11, 2020 4:56:43 PM GMT-03:00, "Gustavo A. R. Silva" <gustavoars@kernel.org> wrote: >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.
Thanks, applied
- Arnaldo > >[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> >--- > 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/branch.h | 2 +- > 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 +- > 15 files changed, 19 insertions(+), 19 deletions(-) > >diff --git a/tools/perf/bench/sched-messaging.c >b/tools/perf/bench/sched-messaging.c >index 97e4a4fb3362..71d830d7b923 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 7e124a7b8bfd..8f983877c42d 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 1f57a7ecdf3d..02d64a9c6f64 100644 >--- a/tools/perf/builtin-script.c >+++ b/tools/perf/builtin-script.c >@@ -2619,7 +2619,7 @@ 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 9e84fae9b096..0ba568efa939 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 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 { >diff --git a/tools/perf/util/branch.h b/tools/perf/util/branch.h >index 154a05cd03af..748f1d23a5c4 100644 >--- a/tools/perf/util/branch.h >+++ b/tools/perf/util/branch.h >@@ -41,7 +41,7 @@ struct branch_entry { > struct branch_stack { > u64 nr; > u64 hw_idx; >- struct branch_entry entries[0]; >+ struct branch_entry entries[]; > }; > > /* >diff --git a/tools/perf/util/cputopo.h b/tools/perf/util/cputopo.h >index 7bf6b811f715..6201c3790d86 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 2db64b79617a..d7ba29ad19ff 100644 >--- a/tools/perf/util/dso.h >+++ b/tools/perf/util/dso.h >@@ -136,7 +136,7 @@ struct dso_cache { > struct rb_node rb_node; > u64 offset; > u64 size; >- char data[0]; >+ char data[]; > }; > > struct auxtrace_cache; >@@ -208,7 +208,7 @@ 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 b8289f160f07..6ae01c3c2ffa 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 e3ccb0ce1938..32bb05e03fb2 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 f2c3823cc81a..ab2842def83d 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 0920fb0ec6cc..75345946c4b9 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 80ff41fc45be..a1d1e4ef6257 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 93fc43db1be3..ff4f4c47e148 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 b4649f5a0c2f..9aededc0bc06 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,
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