Messages in this thread Patch in this message | | | Date | Mon, 11 May 2020 14:56:43 -0500 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH] perf tools: Replace zero-length array with flexible-array |
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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 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, -- 2.26.2
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